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This article was downloaded by: [LMU Muenchen] On: 14 March 2013, At: 01:12 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Journal of Macromolecular Science, Part C Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/lmsc19 Biodegradable Polymers: Challenges and Strategies D. Satyanarayana a & P. R. Chatterji a a Division of Organic Coatings & Polymers, Indian Institute of Chemical Technology, Hyderabad, 500007, India Version of record first published: 23 Sep 2006. To cite this article: D. Satyanarayana & P. R. Chatterji (1993): Biodegradable Polymers: Challenges and Strategies, Journal of Macromolecular Science, Part C, 33:3, 349-368 To link to this article: http://dx.doi.org/10.1080/15321799308021440 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms- and-conditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages

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Page 1: Biodegradable Polymers: Challenges and Strategies

This article was downloaded by: [LMU Muenchen]On: 14 March 2013, At: 01:12Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK

Journal of MacromolecularScience, Part CPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/lmsc19

Biodegradable Polymers:Challenges and StrategiesD. Satyanarayana a & P. R. Chatterji aa Division of Organic Coatings & Polymers, IndianInstitute of Chemical Technology, Hyderabad,500007, IndiaVersion of record first published: 23 Sep 2006.

To cite this article: D. Satyanarayana & P. R. Chatterji (1993): BiodegradablePolymers: Challenges and Strategies, Journal of Macromolecular Science, Part C, 33:3,349-368

To link to this article: http://dx.doi.org/10.1080/15321799308021440

PLEASE SCROLL DOWN FOR ARTICLE

Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions

This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden.

The publisher does not give any warranty express or implied or make anyrepresentation that the contents will be complete or accurate or up todate. The accuracy of any instructions, formulae, and drug doses should beindependently verified with primary sources. The publisher shall not be liablefor any loss, actions, claims, proceedings, demand, or costs or damages

Page 2: Biodegradable Polymers: Challenges and Strategies

whatsoever or howsoever caused arising directly or indirectly in connectionwith or arising out of the use of this material.

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J.M.S.-REV. MACROMOL. CHEM. PHYS., C33(3), 349-368 (1993)

Biodegradable Polymers: Challenges and Strategies'

D. SATYANARAYANA and P. R. CHATTERJI Division of Organic Coatings & Polymers Indian Institute of Chemical Technology Hyderabad 500007, India

1 .

2.

3.

4.

5

6.

INTRODUCTION . . . . . . . ROLE OF ENVIRONMENTAL FACTORS ON BIODEGRADATION . . . . . . . . . . . . . . . . . . . . . . . SYNTHETIC POLYMERS AND BIODEGRADABILITY. . . . . SEARCH FOR SYNTHETIC BIODEGRADABLE POLYMERS.

4.2. Poly(urethanes) , Poly(esters), Poly(amides),

. . . . . . . . . . . . . . . . . . . . . . . . . .

4.1. Hydrophilic Polymers. . . . . . . . . . . . . . . . . . .

4.3. Biosynthetic Pathways. . . . . . . . . . . . . . . . Poly(anhydrides), etc.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.4. Miscellaneous Systems. .

COMPOSITES OF SYNTHETIC AND NATURAL MACROMOLECULES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1. Polysaccharide-Based Systems. . . . . . . . . . . . . . . . . . . . . . . . . 5.2.

CONCLUSIONS . . . . . . . . . . . . . 6.1. Mixed Cultures and Microbial Communities. . . 6.2. Biotechnological Answer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . REFERENCES. . . . . . . . . . . . . . . . . . . . .

Protein-Based Systems. . . . . . . . . . . . .

350

353

354

355 355

355 356 357

357 358 359

359 360 36 1

36 1

'IICT Communication NO. 3097.

349

Copyright @ 1993 by Marcel Dekker, Inc.

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Page 4: Biodegradable Polymers: Challenges and Strategies

350 SATYANARAYANA AND CHATTERJI

1. INTRODUCTION

Synthetic polymers have displaced metals, glasses, ceramics, and wood in many products, especially in the area of packaging. Poly(ethylene), poly(styrene), poly(viny1 chloride), and poly(propylene), in a variety of forms such as films, flexible pouches, and rigid containers, have revolutionized the packaging industry. However, these materials, once discarded, persist in the environment without being degraded, thus giving rise to a multitude of ecological and environmental concerns.

The resistance to natural degradation can be equated to durability or stability. However, the thermodynamic and kinetic interpretations of stability are slightly different. Thermodynamically speaking, no chemical compound is stable eternally. There is every probability that at some stage during the evolutionary process a few microorganisms may develop the necessary catabolic expertise to deal with these manmade materials. Kinetic stability, on the other hand, is defined in terms of more realistic time scales, and many materials may be safely classified as nondegradable. Hence, based on a common reference time frame, synthetic polymers are nondegradable while natural polymers, such as proteins and polysaccharides, are readily degradable. Tables I and 2 list the biodegrada- bility characteristics of some natural and synthetic polymers.

TABLE 1

Natural Polymers and Their Biodegradation Characteristics

Chemical Enzymes responsible No. Natural polymer nature for degradation

Poly saccharides Cellulose Dextran Agar Chitin Starch Proteins Collagen Casein Gelatin Keratin Natural rubber Lignin Nucleic acids

Ether linkages

Amide linkages

Isoprene units Phenolic units Nucleotides

Cellulases Dex tranase Microbial resistant Chitinase Amylase and phosphorylase

Pepsin, chymotrypsin, trypsin, carboxy peptidase, papain

Nucleases

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Page 5: Biodegradable Polymers: Challenges and Strategies

TABLE 2

Synthetic Polymers and Their Biodegradation Characteristics

Degradability No. Synthetic polymer Chemical nature characterstics

1 Resins (a) Aced resins + C R z O +n

@) Acrylic resins + C H 2 - CH -+ I

O = C- 0 - R

(c) Phenolic resins

-4[$cH2- CH2 - /

(d) Amine resins .N-CH2-O - CHz-N, /

(e ) Epoxy resins f 0 -@Tb 0- C H 2 - C H - C H 2

CH3 (f) Phenoxy resins @O-CHz-CH- CHZ- 0

I 0 -

(g) Furan resins

2 Poly(acrylonitri1e)

CN

I R

No biological degradability

h- C % + 5 Poly(propy1ene)

I t H7

(continued)

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352 SATYANARAYANA AND CHATTERJI

TABLE 2. Continued

Degradability No. Synthetic polymer Chemical nature characterstics

6

7

8

9

10

I I

12

13

14

15

16

f CH- CH,-)-,

f c 5 - c 5 + n

f CH2-CH2 t,

Poly(viny1 chloride) I

CI

Poly (fluroethylene)

Poly(viny1 alcohol) f CHI-~H-)~

OH

Poly(ethy1ene)

Poly (esters) + O - C - C H 2 i II 0

0 0 I1 Pol y(amides)

-C-C%-N-C ( I H

Poly (urethanes) H O I II

- N - C - O -

Wet condition susceptible

Low molecular weight and straight chain susceptible

Susceptible

,CH I - N - I H

Aliphatics are susceptible

Susceptible ! ? I Pol y (anhydrides) C . R . C - 0 +n

Poly (ureas) ~ R N C O N R J- n

Pol y (phosphazone) f N = P(OR12 3;;

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BIODEGRADABLE POLYMERS 353

What exactly do we mean by degradation of macromolecules? It is the breakdown of these large carbon compounds into smaller fragments and ultimately into simpler, stable end products. These degradative carbon cycles are run in the soil by aerobic or anaerobic microorganisms, seeking to releaee and harness the energy for their growth. For example, in the highly oxidizing atmosphere of earth, the stablest carbon compound is carbon dioxide. And, indeed, carbon dioxide is the beginning and end of nature's carbon cycle. In contrast, under reducing conditions, the stablest end product of carbon is methane. However, more often than not, the reduction of carbon compounds does not go to completion and a wide range of microbial fermentation products, less reduced than methane, is formed. This depends on the microorganism and the degree of anaerobiosis that favors its growth.

There is general consensus on the need for biodegradable plastics for packaging and other short-term applications. The first logistic step toward the development of biodegradable plastics is a critical appraisal of the various factors influencing biodegradability. This, indeed, is essential because Nature has paradoxically perfected the enzymatic machinery to break down the amide bonds in complex proteins but not those in a seemingly simpler synthetic polyamide (nylon).

2. ROLE OF ENVIRONMENTAL FACTORS ON BIODEGRADATION

Environmental factors play an important role in influencing the microbial attack on any given material. Of these, the following are of main concern.

Water Water is essential for the growth of microbes. Bacteria and lower forms of fungii need a humid habitat. For example, wood is attacked by fungii only when the moisture content is more than 20%.

Microbes need optimum temperatures for growth. At very high or very low temperatures, they are destroyed. Generally, fungii need a temperature range of 20-28 "C and bacteria prefer 28-37 "C. However, there are exceptions. The thermophilic bacteria isolated from hot springs or volcanic sites have an optimum growth temperature of around 100°C. Similarly, antarctic microbes survive in the other climatic extreme of intenve cold.

pH: Each microorganism thrives and operates in specific pH ranges. Fungii can tolerate acidic pH but bacteria favor slightly basic pH. Of course, there are also exceptions in these cases.

Oxygen: The availability of molecular oxygen is an important factor for the growth of microbes. While fungii are generally aerobic, bacteria can be aerobic, anaerobic, or microaerophilic.

Temperature:

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354 SATYANARAYANAAND CHATTERJI

If environmental conditions are conducive, then microbes infest a material, thus ensuring subsequent decay.

3. SYNTHETIC POLYMERS AND BIODEGRADABILITY

Because of their hydrophobic nature, synthetic polymers are generally unable to harbor microbes, but there are some exceptions. Table 2 lists common synthetic polymers and their biodegradability characteristics (1,2). Laboratory- scale biodegradability studies often provide valuable data regarding structure- microbial susceptibiility relationships (3, 4). Standard methods are available for such assessments (5-10). We shall take a closer look at factors affecting the biodegradability of synthetic plastics.

Structure ofthe Plastic: Chemical structure influences the rate and extent of biodegradation. Synthetic and natural polymers are structurally very dissimilar. This makes them different in their biodegradability characteristics too. The effect of chemical structure on biodegradability has been dealt with in detail by Potts et al. (1 1). In some cases, molecular weight is an important factor. High molecular weight poly(ethy1ene) is extremely durable, but low molecular weight samples (< 500) are susceptible to degradation. However, poly(styrenes) are not biodegradable in any molecular weight range. Aliphatic polymers are more vulnerable to microbial attack than their aromatic counterparts.

Functional Groups: Functional groups like -NH2, -COOH, -OH, and -NCO can improve the hydrophilicity of a polymer, thus making it a more attractive habitat for microbes. The degree of susceptibility of some polymers to biodegradation improves when the backbone contains both hydrophilic and hydrophobic segments (12). Alkane diol polymers with C6 and C8 units are more susceptible to biodegradation than polymers containing C2 and C4 or Cl0 and CI2 units.

Brunching: Branching affects biodegradability adversely. Highly branched chains with an effective molecular weight of less than 400 have been found to be bioresistant.

Crosslinking: Crosslinking restricts the mobility of polymer segments and consequently the accessibility of enzymes to susceptible points, thus leading to a decrease in biodegradability.

It is often found that rough surfaces are more susceptible to microbial attack than are smoother surfaces. Perhaps the pits and crevices help to retain moisture and thus promote microbial growth.

Surjiuce Characteristics:

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BIODEGRADABLE POLYMERS 355

4. SEARCH FOR SYNTHETIC BIODEGRADABLE POLYMERS

It is obvious from Table 2 that the common synthetic polymers are resistant to degradation in a realistic time scale, and this has been linked partially to their hydrophobicity. Hence, several strategies have been adopted to induce biodegradability by imparting hydrophilic properties to plastics. Thus, introducing polar groups and synthesizing polymers similar in structure to natural polymers are considered viable alternatives.

4.1. Hydrophilic Polymers

Since wettability is the first and foremost criterion for biodegradability, the development of water-soluble and hydrophilic polymers has received considerable attention. Recently Matsumura et al. (13) and Swift (14) briefly reviewed the literature on water-soluble biodegradable polymers. Such polymers have been recommended as protective coatings for seed (15, 16).

The extent of biodegradability of these polymers depends on the method of preparation and the chemistry of the components used. Materials with 61 % biodegradability can be prepared from maleic anhydride, ethylene glycol, acrylic acid, and p-toluenesulfonic acid. When the components involved are ethylene glycol, diacrylate, acrylic acid, mercaptoethanol, and 2,2 '-azobis-(2-amino propane), the biodegradability improves to 89 % . Water-soluble, microbially- sensitive block copolymers of lysine and styrene have also been reported (17).

Poly(styrene) is one of the most versatile and widely used synthetic plastics used for packaging. Hence, serious attempts have been made to improve its biodegradability (1 8). Systematic investigations have indicated that partially oxidized or hydrolyzed poly(styrene) is broken down by microbes of the Moraxella genus and the fungii of the Penicillium genus (19-2 1) . This could be due to the formation of hydroxyl and carbonyl groups.

4.2. Poly(urethanes), Poly(esters), Poly(amides), Poly(anhydrides), etc.

These synthetic polymers possess backbone structures which bear a chemical resemblance to natural polymers. Hence, some of these are indeed fragmented by microbes with ease. For example, the poly(urethane) backbone resembles the peptide backbone in a protein. The biodegradability of poly(urethanes) has been well documented (22-26). The degradability of poly(capro1actones) depends on their molecular weight (27-29). Low molecular weight poly(ester- urea) containing phenylalanine is readily hydrolyzed by u-chymotrypsin at pH

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356 SATYANARAVANA AND CHATTERJI

7.8. However, if phenylalanine is replaced by glycine, the material turns resistant to chymotrypsin (30).

@-Substituted poly(esters) have been synthesized and tested for biodegradability in acid and alkaline media (3 1). All these esters are in general attacked by microbes, except those with an isotactic structure. Poly(esters) derived from diglycolic acid and lower alkane diols are biodegradable (32). Poly(esters) having carboxy-ortho or ortho-ester linkages are also susceptible to microbial attack (33).

Attempts have been made to synthesize biodegradable derivatives of nylon (34). Several poly(amides) derived from amino acids show not only microbial degradability but biocompatibility as well (35). Poly(amides) derived from cyclic dinitrones and ketocarboxylic acids are biodegradable (36, 37). Poly(amides) containing methyl and hydroxyl groups also behave similarly (38). Hydroxy propyl methacrylamide polymers with peptide linkages are hydrolyzed by papain (39). Biodegradable nonpeptide polyamides have been derived by the ring opening polymerization of bis(oxazo1ones) with diamines, amino alcohols, and aminothiols (40).

Biodegradable poly(amide)-poly(ester) fibers can be prepared by the polycondensation of diamine with 2 moles of glycolic or lactic acid (41). The resulting diamine is subsequently condensed with a dicarboxylic acid. Low molecular weight polymers of poly(keto esters) are susceptible to degradation by Aspergillus niger and Aspergillus flaves (42). The introduction of methyl groups in the chain decreases the susceptibility to fungal attack. Domb (43) recently reported the synthesis of biodegradable aromatic anhydrides. In an interesting study, a computerized approach has been used to predict the rates of biodegradation of poly(anhydrides) (44).

4.3. Biosynthetic Pathways

Biosynthetic pathways have been investigated for the synthesis of several biodegradable poly(esters) (45-57). These poly(esters) are actually poly(@- hydroxy alkanoates) which are intercellular reserve materials accumulated by the Alkaligenus eutrophus bacteria under certain unbalanced growth conditions. In addition to the well-known simple poly(ester), poly(P-hydroxy butyrate) (PHB), various other copolyesters containing other hydroxy acid units such as 3-hydroxy valerate, 4-hydroxy butyrate, and 5-hydroxy valerate have been detected in the cells of these bacteria (58-71). These copolyesters have attracted commercial interest as possible candidates for the large-scale production of biodegradable thermoplastic materials. The blends of these bacterial copoly- esters with poly(ethy1ene) and poly(styrene) are also biodegradable (72).

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BIODEGRADABLE POLYMERS 357

4.4. Miscellaneous Systems

The synthesis of biodegradable block copolymers by condensation and addition reactions has been reported (73). Amide-ester block copolymers prepared from low molecular weight aliphatic esters and amides are sensitive to microbial attack (74). The poly(ester-amide) block copolymers of polycaprolactone and nylon segments interspersed with diisocyanate bridges are susceptible to enzymatic degradation (75, 76). Increasing the aromatic content, however, decreases the susceptibility of the material to enzymatic hydrolysis.

[Poly(urethane-poly(urea)] diblock copolymers, developed by polymerizing the diisocyanate with polyol and a glycol diester of phenylalanine, are attacked by chymotrypsin (77). Ethylene-methylene dioxepane copolymers with considerable biodegradability characteristics are prepared from ethylene and 2-methylene-l,3-dioxepane (78, 79).

Preparation and properties of phosphorus and nitrogen-based bioerodible polymers have been reported by Allcock et al. (80). Phosphazene polymers with good biodegradability have been reported by a group of Russian scientists (8 1). [Ethylene-vinyloxirane] block copolymers with good malleability and biodegradability have also been reported (82).

Biodegradable composites of poly(lactic acid) derivatives and synthetic polymers exhibit excellent thermal and mechanical properties (83). [Acrylonitrile-butadiene-methyl acrylate] terpolymers become sensitive to biodegradation upon mild acid hydrolysis (84). In a similar approach, the microbial degradability of (acrolein-acrylic acid) copolymers can be improved through chemical modification (85). The biodegradability of (1,3-trimethylene carbonate) polymers has been studied in virro and in vivo (86).

5. COMPOSITES OF SYNTHETIC AND NATURAL MACROMOLECULES

Natural polymers are generally biodegradable but they do not possess the necessary thermal or mechanical properties desirable for engineering plastics. On the other hand, the best engineering plastics are obtained from synthetic polymers, but they are very poor in their biodegradability characteristics. Hence, attempts are underway to exploit the complementary characteristics of these two classes of macromolecules by combining them as blends, block or graft copolymers, etc. We shall discuss these systems in detail.

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358 SATYANARAYANAAND CHATTERJI

5.1. Polysaccharide-Based Systems

High molecular weight carbohydrates are generally referred to as polysaccharides. Starch and cellulose, the abundantly available polysaccharides, figure significantly in the preparation of multicomponent biodegradable systems.

5. I . 1 . Starch-Based Systems

The deficiencies in the thermal and mechanical properties of starch have been circumvented by blending it with suitable synthetic polymers or synthesizing graft copolymers (87-93). Surface-modified starch polymers are also biodegradable (94). Such systems satisfy the requirements of thermal stability, minimum interference with flow properties, and minimum disturbance to product quality.

Several methodologies have been reported for the manufacture of biodegradable starch-based films (95- 1 14). These films are useful as agricultural mulches or packaging materials.

The biodegradability of the graft copolymers of starch has been tested. These materials lose their mechanical strength and suffer a weight loss of up to 40% due to substantial degradation of the starch ( I 15-120). Block copolymers containing amylose and polyester segments are also biodegradable (12 1- 124).

5. I . 2 . Cellulose-Based Systems

Cellulose is an abundant natural polymer. Kim et al. (125) reviewed the data on the biodegradability of cellulose block copolymers. Nishiyawa et al. (126), while discussing the problems of developing biodegradable plastics, briefly focused on the properties of cellulose-chitosan composites. The degradation characteristics of block and graft copolymers of cellulose have been reported ( 1 27- 134).

5. I . 3. Lignocellulose Systems

The major components of lignocellulose are cellulose, hemicellulose, and lignin. Lignin is a phenolic compound, generally resistant to microbial degradation, but pretreatment renders it susceptible to the cellulase enzyme (135-140). The grafting of lignocellulose with various vinyl polymers has also been attempted, with quite encouraging results (141- 145)

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BIODEGRADABLE POLYMERS 359

5.2. Protein-Based Systems

The backbone of proteins, the peptide bond, is very sensitive to microbial degradation. However, the very poor thermal properties of proteins restrict their use as engineering materials. Chemical modification through functiorial group derivahtion or through graft copolymerizations can indeed improve their thermal and mechanical properties, and make them less readily degradable. The most studied protein system is gelatin, the hydrolysis fragment of the structural protein collagen (146-149). However, the investigations are still in the realm of basic research, and no process significant enough to be commercialized has been achieved.

6. CONCLUSIONS

We began this review by considering the various factors that influence the attack of microorganisms on macromolecules. We noted that structure and chemistry play significant roles in deciding the biodegradability characteristics of a polymer. Although poly(esters) and poly(amides) bear a structural kinship to natural polymers, the aliphatic straight chain poly(esters) and poly(amides) alone are biodegradable; the aromatic and branched analogues are not. Hence, suitable methods for the synthesis of appropriate aliphatic polymers should be developed. Recent progress in the synthesis of hydrophilic polymers and biosynthetic pathways hold promise for the future. However, while developing synthetic alternatives, it is necessary to be fully aware of the capabilities of the ubiquitous microorganisms.

Since the ultimate applications of biodegradable polymers are for short term uses such as packaging, the synthetic approaches may not prove economically viable. Hence, it is imperative that an earnest search be initiated for cost-effective alternatives. Modifying natural polymers by blending or grafting with suitable synthetic polymers gains significance from this point of view. The ideal choice in this context is cellulose. This natural polymer combines the advantages of being a renewable, nonedible material with a very low cost profile. More important, such a choice will be more conservative of resources and less disruptive of the environment.

This issue of biodegradability of plastics requires bolder and braver approaches under two important counts:

1. The use of mixed cultures and microbial communities in biodegradability evaluation.

2. The biotechnological approach.

We shall discuss these points in detail.

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360 SATYANARAYANAANDCHATTERJI

6.1. Mixed Cultures and Microbial Communities

The standard laboratory procedures for evaluating the microbial degradation of polymers and plastics are inadequate in many respects. These methods overlook the microbial diversity of the natural environment. The laboratory experiments are more in the style of adaptation while the natural situation presents the actualities. Most environments support the growth of a wide range of microorganisms having many different metabolic capabilities. It is inevitable that interactions among these species occur, leading to a combined metabolic attack on the material under study. Indeed, it is a commonly accepted observation that the rate of biodegradation of a given compound is often faster in nature than under laboratory conditions. This clearly indicates the concerted activity of a community of microorganisms and a multiplicity of other factors.

The basic principle of the community-based attack is that the component populations do not separately possess the total capacity to degrade a compound, but collectively the complete metabolic apparatus is present. That is, none of the individual species has a complete set of the genetic information required for the synthesis of the essential enzymes, but each has a part of the total.

Several interesting examples can be cited. A mixed culture from soil throve in a medium with styrene as the sole carbon source, while individual strains did not (150). The most valuable piece of information that was revealed as a bonanza was that the degradation of styrene is through a poly(styrene) pathway. The degradation of crude oil by marine microorganisms is most effective in mixed cultures (151). Even PCBs are degraded faster and more extensively by microbial communities ( 152).

The evolution of certain classes of microbial communities may be an important prerequisite for the evolution of novel degradation pathways. This particularly applies to those communities where the complete degradation mechanism is distributed between two or more species. In this context it is relevant to refer to the studies conducted by Bates and Liu (153). They demonstrated that two Pseudomom needed to grow together as a mixed culture to express the complete lecithinase activity. It was suggested that each species synthesized a different subunit of the enzyme so only a mixed culture could produce the active enzyme. Synergism between cellulolytic and noncellulolytic species was postulated as the reason for the increased extent of cellulose degradation in vivo as compared to that observed in pure culutures of cellulolytic ruminal bacteria in vitro ( 154- 156).

This draws our attention to the most significant single point. Catabolism of a given compound is not monopolized by a individual species. Interactions

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BIODEGRADABLE POLYMERS 361

among different organisms and the integration of different metabolic sequences/capabilities could maximize degradation rates or introduce newer routes.

The possibilities of either finding naturally occurring microbial communities or constructing such systems through judicial manipulation are unlimited. The genetic potential that exists in different organisms in the biosphere could be exploited to our advantage. Similarly, the utility of thermophilic bacteria remains to be explored.

6.2. Biotechnological Answer

Man is guilty of introducing a variety of alien chemicals to Mother Nature as a consequence of technological and scienitific progress. And since nature does not possess the appropriate machinery to deal with these strangers, they persist in the environment. The normal course of most biological processes is tightly regulated at the genetic and physiological levels. Through evolution, each microbial cell achieves a situation of maximum advantage. Genetic engineering encompasses our attempts to perturb this regulation of the cell, so that we may obtain the desired, rather than the normal, outcome. Biotechnoloogy , which implies the technical utilization of biological processes, is now gaining momentum in a number of areas. The prerequisite for the industrial use of biotechnology is the existence of organisms, subcellular particles, or enzymes that can operate on the material in question. For our present issue, we have to put together the necessary catabolic expertise scattered in different species and then transmitted it to others through the agency of plasmids.

For this end, perhaps we should concentrate more on anerobic than on aerobic microbes. This will allow us to control the degradation process without hampering our oxidizing atmosphere. In the highly reducing environment arising from putrefaction and fermentation, the most stable end products will most probably be the hydrocarbons. And if successful, this indeed will be our answer to Nature’s carbon cycle.

REFERENCES

1 . J . P. Scullin, M . D. Dudarevitch, and A. I. Lowell, in Encyclopedia ofPolymer Scienceand Technology, Vol. 2 (H. F. Mark, N. G . Gaylord, and N. M. Bikales, Eds.), Wiley-Interscience, New York, 1965, p . 379.

2 . W. Veerkarnp, Chem. Mag. (The Hague), p. 225 (1981); Chem. Abstr., 95, 3063 (1981).

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3.

4.

5. 6. 7.

8.

9. 10. 11.

12.

13. 14.

15.

16.

17.

18. 19. 20.

21.

22.

23. 24.

25.

P. A. Gilbert and C. M. Lee, Biotransfomtion: The Fate of Chemicals in an Aquatic Environment. Proceedings of a Workshop, p. 34 (1979) (published 1980); Chem. Abstr., 94, 20,131 (1981). R. J. Larson, Ibid., p. 67 (1979) (published 1980); Chem. Abstr., 94, 89,786 (I98 I ) . ASTM Standards, ASTM-G-22, 1976, Part 35, p. 988. ASTM Standards, ASTM-G-21, 1970 (Reapproved 1975), Part 35, p. 983. B. T. Johnson, Biotransformation: The Fate of Chemicals in an Aquatic Environment. Proceedings of a Workshop, p. 25 (1979) (published 1980); Chem. Abstr., 94, 70,877 (1981). P. A. Gilbert, Ecotoxical. Environ. S a t , 3(2), 11 1 (1972); Chem. Absrr., 91, 167,743 (1979). J. Blok, Int. Biodeterior. Bull., 11(3), 78 (1975); Chem. Absrr., 85, 9862 (1976). E. L. Cadmus, J. Coated Fabr., 7(1), 33 (1977); Chem. Abstr., 88,23,678 (1978). J. E. Potts, R. A. Clendinning, and W. B. Ackart, in The Proceedings of Degradability of Polymers and Plastics Conference, Plastic Institute, London, 1973, p. 10/12; Chem. Absrr., 85, 130,108 (1976). S. 3. Huang, in Encyclopedia of Ploymer Science and Engineering, Vol. 2 (H. F. Mark, N . M. Bikales, C . G. Overberger, and G. Menges, Eds.), Wiley- Interscience, New York, 1985, p. 220. S. Matsumura, Zairyo Gijutsu, 8(5), 164 (1990); Chem. Abstr., 113,79,527 (1990). G. Swift, Polyrn. Muter. Sci. Eng. , 63, 846 (1990); Chem. Abstr., 114, 123,098 (1 99 I ) . E. Seelmann, P. Hans, D. Boeckh, H. Hartmann, W. Trieselt, and A. Kud, German Offen. DE 3,713,348; Chem. Abstr., 110, 173,967 (1989). E. Seelmann, P. Hans, D. Boackh, H. Hartmann, and W. Trieselt, German Offen. DE 3,712,326; Chem. Abstr., 110, 155,044 (1989). G. P. Vlasov, G. D. Rudkovskaya, L. A. Ovsyannikova, B. M. Shabsels, and S. V. Martyushin, Vysokomoi. Soedin., Ser. B , 25(2), 126 (1983); Chem. Abstr., 98, 198,829 (1983). H. Hatakeyama, Plast. Age, 23(4), 88 (1977); Chem. Abstr., 87, 136,665 (1977). H . Hatakeyama, Japan Kokai 7738,783; Chem. Abstr., 87, 85,791 (1977). H. Hatakeyama, T. Haraguchi, and E. Hayashi, U.S. Patent 4,154,653; Chem. Abstr., 91, 75,288 (1979). V. W. Mungai, J . A. Cameron, J . F. Johnson and S. J . Huang, Polyrn. Prepr., 30(1), 505 (1989); Chem. Abstr., 110, 213,572 (1989). K. J. Seal and R. A. Pathirana, Int. Biodeterior. Bull., 18, 81 (1982); Chem. Abstr., 98, 143,854 (1983). R. T. Darby, A. M. Kaplan, and M. Arthur, Appl. Microbiol., 16, 900 (1968). S. J. Huang, C. Macri, M. Roby, C. Benedict, and J . A. Cameron, ACS symp. Ser., 172, 471 (1981); Chem. Absrr., 96, 52,821 (1982). F. Y. Shi, L. F. Wang, and K. W. Leong, Polyrn. Prepr., 31(2), 177 (1990); Chem. Abstr., 114, 165,467 (1991).

Dow

nloa

ded

by [

LM

U M

uenc

hen]

at 0

1:12

14

Mar

ch 2

013

Page 17: Biodegradable Polymers: Challenges and Strategies

BIODEGRADABLE POLYMERS 363

26.

27.

28.

29. 30. 31. 32.

33.

34.

35.

36.

37.

38.

39.

40.

41. 42. 43. 44.

45.

46.

47.

48. 49. 50. 51. 52.

Y. Saotome, T. Miyazawa, and T. Endo, Japan Kokai Tokkyo Koho JP 02, 289,619; Chem. Abstr., 114, 165,154 (1991). R. D. Fields, F. Rodriguez, and R. K. Finn, J. Appl. Polym. Sci., 18(12), 3571 (1974). C. V. Benedict, W. J. Cook, P. Jarrett, J. A. Cameron, S. J. Huang, and J. P. Bell, Ibid., 28, 327 (1983). C. V. Benedict, J. A. Cameron, and S . J. Huang, Ibid., 28, 335 (1983). S. J. Huang, D. A. Bansleben, and J. R. Knox, Ibid., 23, 429 (1979). T. Araki and S. Hayase, J . Polym. Sci., Polym. Chem. Ed., 17(6), 1877 (1979). D. J. Casey and G. C. Gleckler, German Offen. 2,454,818; Chem. Absrr., 83, 180,217 (1975). J. Heller, Y. W. Ng. Steve, and W. H. Penhale Donald, U.S. Patent 4,946,936; Chem. Abstr., 114, 247,972 (1991). K. W. Leong, Diss. Absrr. Int. B , 38(1), 216 (1977); Chem. Absrr., 87, 85,430 (1977). M. Iwatsuki and T. Hayashi, Japan Kokai Tokkyo Koho JP 01,283,228; Chem. Absrr., 112, 204,790 (1990). Y. Wu and H. Shiou, Diss. Abstr. Int. E , 38(10), 4837 (1978); Chem. Absrr., 89, 6607 (1978). C. Guaita and G. Semeghini, European Patent Appl. EP 347,687; Chem. Absrr., 112, 218,334 (1990). A. Pavlisko, Diss. Abstr. Inr. B, 39(11), 5401 (1979); Chem. Absrr., 21, 75,048 (1979). R. Ulbrich, E. I. Zacharieva, B. Oboreigner, and J. Kopek, Biomaterials, 1(4), 199 (1980); Chem. Abstr., 94, 104,188 (1989). F. W. Harris and R. P. Eury, Polym. Prepr., 30(1), 449 (1989); Chem. Absrr., 1 1 1 , 78,722 (1989). T. H. Barrows, Braz. Pedido. PI BR, 80,08,027; Chem. Absrr., 99, 38,954 (1983). S. J. Huang and C. A. Byrne, J . Appl. Polym. Sci., 25(9), 1951 (1980). A. J. Domb, Macromolecules, 25, 12 (1992). E. Ron, E. Mathiowitz, G. Mathiowitz, and R. Langer, Polym. Prepr., 30(1), 462 (1989); Chem. Absrr., 111 , 7957 (1989). D. H. Lee, Y. Doi, andK. Soga, Pollimo, 12(2), 129 (1988); Chem. Absrr., 109, 73,925 (1988). R. W. Lenz, R. A. Gross, H. Brandl, and R. C. Fuller, Chin. J . Polym. Sci., 7(4), 289 (1989); Chem. Absrr., 113, 25,180 (1990). M. Kunioka and Y. Doi, Zairyo Gijutsu, 8(4), 125 (1990); Chem. Absrr., 113, 57,333 (1990). Y. Doi, Fragrance J., 18(10), 50 (1990); Chem. Abstr., 114, 63,286 (1991). Y. Doi, Kogaku Kogyo, 41(9), 747 (1990); Chem. Abstr., 114, 205,415 (1991). Y. Doi, Kogaku, 46(1), 76 (1991); Chem. Abstr., 114, 141,474 (1991) Y. Doi, Y. Kanesawa, M. Kunioka, and T. Saito, Macromolecules, 23, 26 (1990). N. D. Miller and D. F. Williams, Biornurerials, 8, 129 (1987); Chem. Absrr., 106, 201,697 (1987).

Dow

nloa

ded

by [

LM

U M

uenc

hen]

at 0

1:12

14

Mar

ch 2

013

Page 18: Biodegradable Polymers: Challenges and Strategies

364 SATYANARAYANAAND CHATTERJI

53.

54. 55.

56.

57. 58.

59.

60.

61.

62.

63.

64. 65.

66.

67.

68.

69.

70.

71.

72.

73.

74.

75,

S. 3. Holland, A. M. Jolly, M. Yasin, and B. J. Tighe, Biomaterials, 8,289 (1987); Chem. Abstr., 107, 161,622 (1987). P. A. Holmes, Phys. Technol., 16, 32 (1985); Chem. Abstr., 102, 133,129(1985). P. A. Holmes, U.K. Patent Appl. GB 2,160,208; Chem. Abstr., 104, 230,469 (1986). M. Kuniokaand Y. Doi, Dojin News, 49, 3 (1989); Chem. Abstr., 111, 134,777 (1989). P. P. King, J . Chem. Technol. Biotechnol., 32, 2 (1982). Y. Doi, M. Kunioka, Y. Kawaguchi, A. Segawa, C. Abe, and Y. Kansawa, Polym. Prepr., 30(1), 494 (1989); Chem. Abstr., 111, 115,867 (1989). P. A. Holmes, L. F. Wright and S . H. Collins, European Patent Appl. EP 52,459; Chem. Abstr., 97, 143,146 (1982). P. A. Holmes, L. F. Wright, and S. H. Collins, European Patent Appl. EP 69,497; Chem. Absrr., 98, 141,883 (1983). P. A. Holmes, S. H. Collins, and L. F. Wright, U.S. Patent 4,477,654; Chem. Abstr., 102, 4469 (1985). Y. Doi, M. Kunioka, Y. Nakamura, and K. Soga, Macromolecules, 19, 2860 (1986). Y. Doi, M. Kunioka, Y. Nakamura, and K. Soga, J . Chem. SOC., Chem. Commun., 23, 1696 (1986). Y. Doi, A. Tamaki, M. Kunioka, and K. Soga, [bid., 21, 1635 (1987). Y. Doi, M. Kunioka, Y. Nakamura, and K. Soga, Macromolecules, 20, 2988 (1987). Y. Doi, A. Tamaki, M. Kunioka, and K. Soga, Makromol. Chem., Rapid Commun., 8(12), 631 (1987); Chem. Abstr., 108, 36,305 (1988). Y. Doi, A. Tamaki, M. Kunioka, and K. Soga, Appl. Microbiol. Biotechnul., 28, 330 (1988); Chem. Abstr., 109, 53,165 (1988). Y. Doi, M. Kunioka, and A. Tamaki, Pulym. Prepr., 29, 588 (1988); Chem. Abstr., 109, 55,353 (1988). Y. Doi, M. Kunioka, Y. Nakamura, and K. Soga, Macromolecules, 21, 2722 (1988). M. Kunioka, Y. Nakamura, and Y. Doi, Polym. Commun., 29, 174 (1988); Chem. Abstr., 109, 74,036 (1988). M. Kunioka, Y. Kawaguchi, and Y. Doi, Appl. Microbiol. Biotechnol., 30,569 (1989); Chem. Abstr., 111, 55,772 (1989). S.N. Bhalakia, T . Patel, R. A. Gross, and S . P. McCarthy, Polym. Prepr., 31(1), 441 (1990); Chem. Abstr., 114, 7600 (1991). B. G. Penn, Diss. Abstr. Int. B, 39 (3, 2330 (1978); Chem. Abstr., 90, 55,325 (1979). Y. Tokiwa, T. Suzuki, Y. Takahara, and T. Ando, Japan Kokai Tokkyo Koho 79,119,595; Chem. Abstr., 92, 59,668 (1980). J . P. Bell, S. J. Huang, and J. R. Knox, Gov. Rep. Announce. Index (U.S . ) , 76(24), 89 (1976); Chem. Abstr., 86, 73,472 (1977).

Dow

nloa

ded

by [

LM

U M

uenc

hen]

at 0

1:12

14

Mar

ch 2

013

Page 19: Biodegradable Polymers: Challenges and Strategies

BIODEGRADABLE POLYMERS 365

76. 77.

78.

79.

80.

81.

82.

83.

84.

85.

86.

87.

88.

89.

90.

91.

92. 93.

94.

95.

96.

97.

Y. Tokiwa and T. Suzuki, J. Appl. Polym. Sci., 26, 441 (1981). I . I. Gladyr, D. V. Vasilchenko, N . N. Bufius, andG. A. Pkhakadze, Vysokomol. Soedin., Ser. B, 31(3), 196 (1989); Chem. Absrr., 111, 24,063 (1989). W. J. Bailey and B. Gapud, ACS Symp. (Polym. Srab. Dograd), p. 423 (1985); Chem. Abstr., 103, 196,477 (1985). B. D. Gapud, Diss. Abstr. Inr. B , 43(6), 1848 (1982); Chem. Absrr.. 98, 54,602 (1983). H. R. Allcock, S. Kwon, and S. R. Pucher, Polym. Prepr., 31(2), 180 (1990); Chem. Abstr., 114, 165,216 (1991). S. I. Belykh, A. B. Davydov, N. N . Kanshin, V. V. Kireev, V. V. Keshelava, Yu. A. Pyttel, E. V. Firsova, and V. P. Kharchenko, USSR Patent SU 1,063,805; Chem. Abstr., 100, 157,571 (1984). Y. Origasa, S. Kojima, K. Suga, and T. Endo, Japan Kokai Tokkyo Koho JP 62,280,218; Chem. Abstr., 108, 151,166 (1988). R. G. Sinclair and J. R. Preston, U.S. Patent Appl. 229,896; Chem. Absrr., 113, 116,458 (1990). S. G. Gilbart, K. J. Giacin, T. Van Gordon, A. Vahidi, and J. R. Giacin, Am. Chem. Soc., Div. Org. Coat. Plasr. Chem., Pap., 34(2), 462 (1974); Chem. Abstr., 85, 22,158 (1976). H. Haschke and G. Marlock, German Offen. 2,357,036; Chem. Absrr., 83, 117,609 (1975). K. J. Zhu, R. W. Hendren, K. Jensen, and C. G. Pitt, Macromolecules, 24, 1736 ( 199 1). J . Silbiger, D. Lentz, and J. P. Sachetto, European Patent Appl. EP 408,503; Chem. Absrr., 114, 187,881 (1991). C. Bastioli, V. Bellotti, G. L. Del, and R. Lombi, PCT Int. Appl. WO 91,02,024; Chem. Abstr., 114, 230,128 (1991). C. Bastioli, R. Lombi, T. G. Del, and I. Guanella, European Patent Appl. EP 400,531; Chem. Abstr.. 114, 64,660 (1991). C. Bastioli, V. Bellotti, and T. G. Del, PCT Int. Appl. WO 91,02,025; Chem. Absrr., 114, 230,129 (1991). R. Sugita and A. Tokutake, Nisseki Rebyu, 32(4), 169 (1990); Chem. Absrr., 114, 208,716 (1991). B. N. Agarwal, Pop. Plasr. Packag, 16, 45 (1991). F. H. Otey, Renewable Resour. P h t . Growth Change Adhes. Chem. Requir. Tob. Ind. Symp., p. 87 (1975); Chem. Abstr., 87, 185,309 (1977). W. J. Maddever and G. M. Chapman, Plasr. Eng., 45(7), 31 (1989); Chem. Abstr., 112, 57,378 (1990). F. H. Otey, A. M. Mark, C. L. Mehltretter, and C. R. Russell, I d . Eng. Chem., Prod. Res. Dev., 13(1), 90 (1974); Chem. Abstr., 80, 146,632 (1974). G. J. L. Griffin, Adv. Chem, Ser., 134, 159 (1974); Chem. Absrr., 83, 115,635 (1975). Personal Products Co., Belgian Patent 827,809; Chem. Abstr., 85, 79,100 (1976).

Dow

nloa

ded

by [

LM

U M

uenc

hen]

at 0

1:12

14

Mar

ch 2

013

Page 20: Biodegradable Polymers: Challenges and Strategies

366 SATYANARAYANAANDCHATTERJI

98. F. H. Otey, R. P. Westhoff, and W . M. Doane, Ind. Eng. Chem., Prod. Res. Dev., 19(4), 592 (1980); Chem. Absrr., 93, 205,487 (1980).

99. Oesterreichische Agar Industrie G.m.b.H., Austrian Patent AT 365,619; Chem. Absrr., 97, 24,919 (1982).

100. N. L. Lacourse and P. A. Altieri, U.S. Patent 4,863,655; Chem. Abstr., 112, 58,640 (1990).

101. H. Roper and H . Koch, Starch/Staerke, 42, 123 (1990); Chem. Abstr., 113, 24,537 (1990).

102. Personal Products Co., Netherlands Patent Appl. 75,04,183; Chem. Abstr., 86, 73,798 (1977).

103. Agency of Industrial Sciences and Technology, Japan Kokai Tokkyo Koho JP 02,02,303; Chem. Abstr., 112, 200,981 (1990).

104. G . J. L. Griffin, U S . Patent 4,125,495; Chem. Absrr., 90, 55,817 (1979). 105. Personal Products Co., Austrian Patent 336,195; Chem. Abstr., 87, 40,420

(1977). 106. S. Joseph andT. H. John, U.S. Patent 3,137,664; Chem. Absrr., 61,5874 (1964). 107. F. H. Otey, R. P. Wasthoff, and C. R. Russell, Ind. Eng. Chem., Prod. Res.

Dev., 16(4), 305 (1977); Chem. Absrr., 87, 185,424 (1977). 108. R. P. Westhoff, F. H. Otey, C. L. Mehltretter, and C . R. Russell, Ibid., 132).

123 (1974); Chem. Absrr., 81, 64,534 (1974). 109. F. H. Otey, R. P. Wasthoff, W. F. Kwolek, C . L. Mehltretter, and C. E. Rist,

Ibid., 8(3), 267 (1969); Chem. Abstr., 71, 82,001 (1969). 110. Nichiden Kagaku Co. Ltd., Japan Kokai Tokkyo Koho 81,76,437; Chem. Abstr.,

95, 170,402 (1981). 11 1. G. J. L. Griffin, German Offen. 2,322,440; Chem. Abstr., 80, 134,242 (1974). 112. S. Nanbu and K. Murakami, Tohoku Daigaku Hisuiyoeki Kagaku Kenkyusho

Hokoku, 24(1), 57 (1974); Chem. Abstr., 82, 86,985 (1975). 113. G. J . I. Griffin, British Patent 1,524,821; Chem. Abstr., 90, 205,194 (1979). 114. J. M. Aime, G . Mention, and A. Thouzeau, French Demands FR 2,610,635;

Chem. Absrr., 110, 116,052 (1989). 115. R. J. Dennenberg, R. J. Bothast, and T. P. Abbott, J . Appl. Polym. Sci., 22,

459 (1978). 116. G . F. Fanta, C . L. Swanson, R. C. Burr, and W. M. Doane, Ibid., 28, 2455

(1983). 117. J. J. Meister, G. Merriman, K. Anderly, A. Lathia, F. F. Chang, C. Li, and

S . G. Kim, Polym. Prepr., 30(1), 511 (1989); Chem. Absrr., 110, 213,573 (1989). 118. F. H. Otey, R. P. Westhoff, and C. R. Russell, Ind. Eng. Chem., Prod. Res.

Dev., 15(2), 139 (1976); Chem. Abstr., 85, 22,238 (1976). 119. H. S. Primack and S. H. Carr, Am. Chem. Soc., Div. Org. Cout. Plust. Chem.,

Pap., 34(1), 672 (1974); Chem. Absrr., 84, 60,384 (1976). 120. R. Narayan, Z. J. Lu, Z. X. Chen, and N. Stacy, Polym. Prepr., 29(2), 106

(1988); Chem. Abstr., 110, 9994 (1989). 121. M. M. Lynn, Diss. Abstr. In?. B , 39(5), 2330 (1978); Chem. Absrr., 90, 55,324

(1979).

Dow

nloa

ded

by [

LM

U M

uenc

hen]

at 0

1:12

14

Mar

ch 2

013

Page 21: Biodegradable Polymers: Challenges and Strategies

BIODEGRADABLE POLYMERS 367

122. 123.

124.

125.

126.

127.

128. 129.

130.

131.

132.

133.

134.

135.

136.

137.

138. 139.

140. 141. 142. 143. 144. 145. 146.

147.

K. S. Lee, Ibid., 42(7), 2856 (1982); Chem. Absrr., 96, 86,043 (1982). M. M. Lynn, V. T. Stannett, and R. D. Gilbert, J. Polym. Sci., Polym. Chem. Ed., 18, 1967 (1980). M. M. Lynn, V. T. Stannett, and R. D. Gilbert, Polym. Prepr., 19(2), 106 (1978); Chem. Abstr., 93, 133,168 (1980). S. Kim, V. T. Stannett, and R. D. Gilbert, J. Mucromol. Sci.-Chem., A10(4), 671 (1976); Chem. Absrr., 85, 193,934 (1976). M. Nishiyawa and J. Hosokawa, KogyoZairo, 38(1), 47 (1990); Chem. Abstr., 112, 217,960 (1990). C. David and P. Thiry, Proc. IUPAC, IUPACMacromol. Symp., p. 301 (1982); Chem. Abstr., 99, 141,725 (19831. C. David and P. Thiry, J. Appl. Polym. Sci., 27, 2395 (1982). R. D. Gilbert, V . Stannett, C. G. Pitt, and A. Schindler, Dev. Polym. Degrud., 4 , 259 (1982); Chem. Abstr., 98, 161,178 (1983). M. Lapointe and H. Cheradame, Rev. ATIP, 40(5), 261 (1986); Chem. Absrr., 105, 154,878 (1986). S. Kim, V. T. Stannett and R. D. Gilbert, J. Polym. Sci., Po/ym. Lett. Ed., 11(12), 731 (1973). K . Antos, P. Hodul, E. Markusovska, A. Blazej and R. Borovsky, Czechoslovakian Patent CS, 214,392; Chem. Absrr., 101, 194,172 (1984). B. G. Penn, V. T. Stannett, and R. D. Gilbert, J. Mucromol. Sci.-Chem., A16(2), 473 (1981); Chem. Abstr., 95, 63,937 (1981). B. G. Penn, V. T. Stannett, and R. D. Gilbert, Ibid., A16(2), 481 (1981); Chem. Abstr., 94, 141,442 (1981). C. David, R. Fornasier, and P. Thiry, Polym. Prepr., 24, 439 (1983); Chem. Abstr., 100, 155,192 (1984). C. David and T. Atarhouch, Appl. Biochem. Biorechnol., 16,51 (1987); Chem. Absrr., 109, 172,326 (1988). C. David, P. Thiry, and R. Fornasier, European Patent Appl. EP 89,077; Chem. Absrr., 99, 214,393 (1983). C. David and R. Fornasier, Macromolecules 19, 552 (1986). C. David, R. Fornasier, C. Graindalfallon, and N. Vanlautem, Biotechnol. Bioeng., 27, 1591 (1985); Chem. Absrr., 103, 213,363 (1985). M. Paillet and A. Peguy, J. Appl. Polym. Sci., 40, 427 (1990). L. H. Carvallho and A. Rudin, Ibid., 29, 2921 (1984). R. B. Phillips, W. Brown, and V. T. Stannett, Ibid., 16, 1 (1972). R. B. Phillips, W. Brown, and V. T. Stannett, Ibid., 15, 2929 (1971). R. Chen, B. V. Kokta and J . L. Valade, Ibid., 25, 2211 (1980). R. Chen, B. V. Kokta, and J. L. Valade, Ibid., 24, 1609 (1979). S. J. Huang and K. W. Leong, Polym. Prepr., 20(2), 552 (1979); Chem. Abstr., 95, 133,570 (1981). G. Sudesh Kumar, V. Kalpagarn, and U. S . Nandi, J. Appl. Polym. Sci., 30, 609 (1985).

Dow

nloa

ded

by [

LM

U M

uenc

hen]

at 0

1:12

14

Mar

ch 2

013

Page 22: Biodegradable Polymers: Challenges and Strategies

368 SATYANARAYANAANDCHATTERJI

148.

149.

150.

151. 152. 153. 154. 155. 156.

G. Sudesh Kumar, V. Kalpagam, U. S. Nandi, and V. N . Vasentharajan, fbid., 26, 3633 (1981). D. S. Min, K . H . Lee, and K. Y . Kim, Pollimo, 8(3), 185 (1984); Chem. Absrr., 101, 136,990 (1984). M . Sielicki, D. D. Focht, and J . P. Martin, Appl. Environ. Microbiol., 35, 124 (1978). A . Horowitz, D. Gutrick, and E. Rosenberg, Appl. Microbiol., 30, 10 (1975). G. S. Sayler, M . Shas, and R. R . Colwall, Microb. Ecol., 3, 241 (1977). J . L. Bates and P. V . Liu, J . Bacreriol. 86, 585 (1963). J. M. Osborne and B. A. Dehority, Appl. Environ. Microbiol., 55, 2247 (1989). B. G. Kock and A. Kistner, J . Gen. Microbiol.. 55, 459 (1969). J . A. Coen and B . A. Dehortiy, Appl. Microbiol., 20, 362 (1970).

Dow

nloa

ded

by [

LM

U M

uenc

hen]

at 0

1:12

14

Mar

ch 2

013