The use of aluminium chloride as the alkylation catalyst re-sults in a higher proportion of 2-phenyl isomers than doesthe use of hydrogen fluoride.

CC"W&_,"_CWW"-,,w--wo_w,Lineares Alkylbenzolsu/fonat (LAS) ist von Mikroorganismen-Mischkulturen -wie sie unter natürlichen Bedingungen, aberauch in Kliiranlagen vorliegen -gut abbaubar (95 % MBAS.> 80 % DOC). Die analytisch fajJbaren Zwischenprodukte rei-chem sich im Wasser nicht ano Laboruntersuchungen zeigten.dajJ an der LAS-Mineralisation enzymatisch unterschiedlichausgestattete Bakterienarten beteiligt sin d., Die ersten Abbau-schritte bestehen in der (I)- und {3-0xidation der Alkylkette zuSu/fophenylcarbonsiiuren mil einer Liinge von 4-5 C-Atomen.Die niichste Phase stellen die Ringoffnung (Meta-Spaltung)und die Desu/fonierung dar. Die weiteren Oxidationsschritteflihren zu Verbindungen, die in zentrale Stoffwechselwege derZelle (Tricarbonsiiure- und Glyoxylat-Zyklus) einmünden, umdort einem weiteren Energiegewinn oder dem Anabolismus zudienen.

2 Primary and total degradation

Under the test criteria of Gerrnany- and EEC-wide a surfact-ants legislation, which is based on primary degradation(MBAS reduction), LAS has proven to be very readily de-gradable (95 % reduction in MBAS in the OECD screeningor confirrnatory test). LAS has therefore become a "biologi-cally soft" reference substance in the OECD screening test.However, LAS is also included amongst readily degradablecompounds under the assessment criteria of the ChemicalsAct, which is primarily concerned with the extent of finaldegradation of a substance.

Thus, for example, a DOC decrease of 75 % was found forMarlon@A in the modified OECD screening test, and a DOCdecrease of 73 :t 6 % in the coupled-units version of theOECD confirrnatory test at a residence time of 3 hours [1];indeed, the DOC decrease was 94 :t 5 % at a residence timeof 6 hours [2]. The wealth of literature concerned with thedegradation of LAS has been reviewed in detail by Swisher[3], together with bis own extensive work.

Mixed cultures of microorganisms which can be found undernatural conditions or in sewage treatment plants degrade linearalkylbenzenesulphonate readily (95% MBAS. > 80% DOC).Ihe catabolites do not accumulate in water. Due to laboratoryinvestigations LAS mineralisation is accomplished by differentmicroorganisms with different enzyme pattems. Ihe first stepsin the degradation are w- and {J-oxidations of the alkyl chain.Ihe resulting sulphocarboxylic acids have a length of 4-5C atoms. Ihe next steps are the splitting of the aromatic ringand the subsequent desulphonation. Ihe catabolites of the fur-ther oxidation steps are introduced into the central metabolicpathways (Krebs cycle and glyoxylate cycle).

2.1

DOC and COD degradation

1 Introduction

Table 1 shows the results of a variety of degradation experi-ments. The degradation criterion used was the DOC or CODdecrease. In each case, the oxygen consumption [4] and theevolution of carbon dioxide [1] were assessed as degradationparameters.

In this table, the data determined by Gerike [1 and 5] areof particular interest since they illustrate the different degra-dation efficiencies of eight different test methods. The lowextent of degradation in the MITI and AFNOR tests areclearly attributable to an insufficient biological potentialwhich is inherent in these test methods. In the remaining testsystems, LAS has been found to be readily degradable. Par-ticularly high degradability scores are achieved in the EPA-HAS and Zahn- Wellens tests, i. e. in test systems which aresuitable for detection of basical biodegradability.

In a test method developed by Gerike [6] for determina-tion of catabolites of low degradability and based on thecoupled-units test principIe, LAS was found to be biódegrad-able to the extent of 95 :t 1 %. It can safely be assumed thatthe non-degraded remainder of 4-6 % does not consist of

The synthetic compound linear alkylbenzenesulphonate(LAS) is one of the most thoroughly investigated with respectto biodegradability. The reason for the considerable interestin this surfactant is the understandable concern that the aro-matic ring of the molecule mar be bioresistant and thus ac-cumulate in surface water and reach drinking water. Thanksto intensive study not only of primary and total degradation,but algo of catabolism of LAS by microorganisms, we nowknow that linear alkylbenzenesulphonates are mineralised bi-ologically to form carbon dioxide, water and sulphate. Thediscussion below is a summary of our knowledge ofthe basicprincipies of LAS biodegradation.

For general information, let us recall the constitutionalformula of LAS (Fig.1). With the exception of the two termi-nal methyl groups, the aromatic ring is distributed randomlyover the linear alkyl chain containing 10-13 carbon atoms. H3C -CH2-CH-(CH2),_,- CH3

(* Lecture given at the Intemational Status Seminar "Alkylbenzene

Sulphonate (LAS)" in Aachen/FRG Nov. 9th-10th, 1988.Fig.1. Structural formula of a linearC 10- C I ]-alkylbenz en esulph onu te

~SO~-I Nal+¡

TensideSurfactants Detergents 26 (1989) 286

P. Schoberl, Marl/FRG

Bas]lc PrincipIes of LAS

non easily degradable LAS degradation products, but insteadof impurities resulting from the synthetic process. It wasshown that these toa are not bioresistant. Before the last-mentioned method became available for detecting minerali-saliDo of LAS, the principal interest was naturally in thequestion of whether the aromatic molecular fraction of LASis degraded.

2.2

Degradation o/ the sulfophenyl radical

This question was initially investigated using UV spectro-scopic analysis. Numerous papers, predominantly by Swisher[3], show the aromatic ring to be degradable to the extent of80 %. However, experimental results in so me cases clearly be-low 80% have also been published. These results can beattributed, at least in part, to unsuitable test methods withrespect to the range of organisms, the acclimatization condi-tions and the growth conditions.

More reliable than UV analysis is the tracer technique us-ing 14C ring-Iabelled alkylbenzenesulphonate. The measure-ment of 14CO2 which is carried out during the degradationprocesses has the following essential advantages:a) The sensitivity of the method allows realistically low LAS

concentrations to be used.b) 14C analysis is not impaired by constituents of synthetic or

natural effiuent.c) It is possible to work out a balance ifthe analytical equip-

ment available is suitable.Table 2 summarises the results of such experiments. The de-gradation relating to the labelled ring is predominantly be-tween 50 and 80%. An exception is the value of 4% deter-mined by Phillips [7]. In this case, MBAS degradation is alsoonly 25 %. This indicates a very low biological potential ofthe test batch.

Steber [8] investigated the degradation of a 14C ring-Ia-belled Clo-CI3-LAS in a miniaturised, closed OECD confir-

Table 2. [3J Ring Biodegradation in Ring-Labelled L.4S

Chain I 14C distribution, % in

length I 14CO2 Biomass ]

TestmethodaDO14C

DADASCASDACASDASCASSCAS+DASCAS+DARWRWRWEWRW

12; 131211-1312(40)10-1310-1311-1311-1311-131212121212

a CAS = continuous-flow activated sludge; DA = dieaway in inoculated mineral medium; EW = dieaway in model ecosystem effiuentRW = river water dieaway; SCAS = semicontinuous activated sludge.

b Associated with 500 ppm sediment in the river water." = benzenering

87Tenside Surfactants Detergents 26 (1989) 2

Table 3. Distribution o/ 14C ring-labelling o/ LAS in the continuousactivated-sludge test (OECD)

Table 4. Analytical determination 01 the LAS degradation products inthe discharge Irom an OECD conjirmatory test apparatus (mean resi-dence time 3 hours; synthetic sewage without sulphate)

matory test apparatus (aeration vessel capacity 300 mi) in ac-cordance with the experimental criteria of the official testprocedure. The 14C-LAS introduction phase extended over amaximum of five days.

The balance of the labelling distribution is summarised inTable 3.

From the experimental results, it can be concluded that alabelling equilibrium is not established within the period offive days used for labelling. On the basis of the biological"turnover", which obviously requires more time and is in-complete, the amount of 14C02 liberated at the terminationof the experiment is only 50 %. The majority of the labelledcomponents found in the activated sludge (21-26%) appearsas 14C02 when turnover is cqmplete and must be regarded asdegraded. The microbial ring reaction thus proceeds to theextent of 70-80% during the selected mean residence time of3 hours.

The elimination and quantitative determination of inor-ganic sulphate in the culture solution is a useful indication ofmicrobial attack on the aromatic ring. Numerous experi-mental results have been published, of which those byKrüger[9] and Wickbold[10] are described in detail here. Thedischarge from a normally operated OECD confirmatory testapparatus (mean residence time 3 hours) was subjected tocoarse fractionation and gave the results shown in Table 4.

When determining the ring degradation via the liberationof sulphate, it must be remembered that some of the sulfatebound in the LAS -as such or possibly bound lo low-molec-ular weight aliphatic compounds -is incorporated into thebiomass and thus withdrawn from the balance.

Table 5 shows the results from further experiments for de-termination of ring degradation from the sulphate liberated.The generallY lower findings from the experiments using 358sulphate cannot be explained without additional data, suchas the 35S content of the biomass.

Compilation of the above results for investigation of pri-mary and total degradation (DOC, COD, 14C and 804")shows that LAS can be mineralised biologically. In additionto this finding, however, knowledge of the catabolism of al-kylbenzenesulphonate, i. e. the degradation pathway, is nec-essary to be able to explain why LAS -measured by total pa-rameter analyses -is not 100% degradable in laboratoryexperiments.

Table 5. [3J Inorganic Sulfatefrom LAS Biodegradation~-

Chain length Percent of theoretical

SO42- 35S042-

Methoda Time Ref

8 (20)10 (20)10-1312?12 (20)12131510-1310-13

9693

2d2d

20 d184 d

6 hr6 hr6 hr6 hr

Ryckman, 1956, 1957Ryckman, 1956, 1957Klein 1964aPitter 1964cSharrnan 1964aSweeney 1964aSweeneySweeneySweeneyKlein 1965a,bKlein 1966,McGauhey 1966McGauhey 1966Cordong 1968bCardan 1970Oba 1971Swisher 1972aGledhill1975aHollis 1976b

SCASSCASST + soilDAAQCASCASCASCASTFTF

CASDADADASFDADA

91-96

10-1310-13 (?)12 (20)?12 (30)10-1410-13

8 hr13 d20 d6 d(?)14 d28 d7d

8384

8"" 100

75250

a AQ = dieaway in aquarium; CAS = continuous-flow activated sludge; DA = dieaway in inoculated mineral medium; SCAS = semicon-tinuous activated sludge; SF = shake flask; ST = septic tank; TF = trickling filter.

" = benzenering

88 Tenside Surfactants Detergents 26 (1989) 2

Fig.2. Possible routes for intermediate forma-tion in the oxidation of an alkane to form thefatty acid

3 LAS degradation pathways b) Oxidative shortening of the alkyl chain by 2 carbon units(p-oxidation).

c) Oxidative ring splitting.d) Cleavage ofthe carbon-sulphur bond, i.e. sulphate libera-

tion.The individual steps are discussed below.

3.1 Oxidation of the alkyl chain

Oxidative attack on the alkyl chain at one of the terminalmethyl groups proceeds by the same mechanism used foroxidation of aliphatic hydrocarbons, i. e. via the hydroperox-ide (?), the alcohol, the aldehyde and the carboxylic acid(Fig.2). The first detectable degradation product of LAS isthe (J)-carboxylate. For example, Huddelston and Allred [12Jdetected sulphophenyldecanoic acid as a catabolite of 2-ben-zen edecanesul phonate.

Bacteria which convert LAS los e the ability to oxidizeLAS during cultivation on LAS-free media. Reactivation ispossible through short-chain or long-chain aliphatic alco-hols, aldehydes or carboxylic acids, but not by LAS itself.Obviously, the induction substrate may not contain a ring ifthe repressor of LAS permease -this appears to be the targetenzyme -is to be eliminated [13]. This means that an appro-priate co-substrate must be present during first contact ofLAS with the bacteria in question.

Oxidative degradation of the alkyl chain commences assoon as the LAS has been converted into sulphophenyl-car-boxylic acid. Although shortening of the alkyl chain by a-ox-idation has been detected, it only appears to be a secondaryroute [14 and 15J (Fig.3). The principal degradation pathwayis IJ-oxidation. According to Divo and Cardini [16J andSchoberl and Kunkel [17], this chain shortening, which takesplace in steps involving 2 carbon atoms, continues until thealkyl chain only has 4-5 carbon atoms. Oxidative conver-sion of the benzene ring then cornmences.

3.2 Benzene ring degradation

LAS catabolism confronts the microorganisms -generalIybacteria -involved in it with the task of being able to converta very wide variety of structures, namely the aliphatic chainwith a non-uniform number of carbon atoms, the aromaticring, which is, in addition, distributed randomly over the al-kyl chain, and cleavage of the carbon-sulphur bond on thebenzene ring. Since not alI the organisms involved in LASdegradation have fulI enzymatic potential for conversion ofalI the structures mentioned, different species or genera ofbacteria are frequently involved in catabolism of the LASmolecule.

In organisms which have fulI enzymatic potential, induc-tion processes or even, from the steric point of view, enzymeconfiguration changes [3] may nevertheless be necessary.

It is therefore not surprising that mixed cultures are fre-quently more efficient than single-celI cultures with respectto LAS mineralisation.

However, the use of pure cultures is necessary in caseswhere it is important to explain individual catabolic path-ways. Cain. Willats and Bird [11] detected five different typesof reaction in this way:a) (J)-oxidation with subsequent p.oxidation of the aliphatic

chain, but no desulphonation and no degradation of thebenzene ring.

b) (J)-oxidation and subsequent p.oxidation with simulta-neous desulphonation and ring splitting.

c) As in b), but accompanied by reductive desulphonation.In this way, phenylalkanoate is produced instead of p-hy-droxyphenylalkanoate.

d) a-oxidation with subsequent ¡J-oxidation and ring desul-phonation without attack on the ring itself.

e) If the alkyl chain has a low number of carbons «4), bi-odegradation begins on the benzene ring, either by thehydrolytic route or in some cases by reductive ring desul-phonation.

In overalI terms -the way the processes should be looked atin nature and in water-treatment plants -the LAS degrada-tion pathway now looks as folIows:a) Oxidative conversion of one of the two methyl groups of

the alkyl chain into a carboxyl group «(J)-oxidation).The primary step comprises incorporation of molecular oxy-gen (Fig.4).

Tenside Surfactants Detergents 26 (1989) 2 89

P. SchoberI: Basic PrincipIes of LAS Biodegradation

CH)-(CH2rn-CH2-CH)./ ".,/ c~ ;~-CH3

CH

O ~HOHH

".

"CH3-(CH2)n-CH2-COOH

\'\ 101- Oxidation

\HOOC -(CH2In-CH2-COOH

j '-00;"""

, o" 11

t ~CH3-(CHVn-(-COOH[J-Oxidation

Decarboxylation,then f3~Oxidation

~

The mechanism appropriate to LAS is obviously metaclea-vage.

Baggi [18] (Fig.6) was able to detect 2-(2,3-dihydro-2,3-di-hydroxyphenyl)butane and 3-(2,3-dihydro-2,3-dihydroxyphe-nyl)pentane in pure cultures (Pseudomonas pulida and Pseu-domonas acidovorans), which oxidized 2-phenylbutane and3-phenylpentane respectively. In these catabolites the ringopening took place by the meta-cleavage mechanism. The

Acetate Acetate+ Succinate Acetate

Fig.3. Degradation of alkanes to form acetate and small amounts ofsuccinate (produced in particular from alkane chains having an oddnumber of C atoms)

The first oxidation product, but one which has hithertonot been detected, is probably a cyclic peroxide, which isconverted into pyrocatechol in the presence of the coenzymeNAD+. In metabolic physiology of microorganisms, threeprincipal mechanisms are known for ring opening of dihy-droxylated aromatic rings (Fig.5).

Of these three possibilities, orthocleavage of pyrocatecholis only applicable if the ring does not contain a sirle chain.

Fig.4. Oxidation 01 aromatic hydrocarbons bybacteria or in mammalian liver cells

Fig.5. Various types o/ microbial cleavage o/aromatic rings

90 Tenside Surfactants Detergents 26 (1989) 2

[H)-([HZln-[ -CH)III! IX-Oxidation

P. Schoberl: Basic PrincipIes of LAS Biodegradation

~HJ rHJCO .CO2H

- Ú O2H CH3 Crl.-H

-I ,v¿

OH CHO/COCH3

--Fig.7. m-Cleavage according lO Fochl and Williams

Y""'Y ~ l¡ .l!i.. ~sÜJ-

Rd HO °2H

OH

RC OH

OH

R~ -~

~SÜ3-.!!2-

Fig080 m-Cleavage according to Cain, Bird and Johnston

chemical structure identified (2-hydroxy-6-keto-7-ethyl-nona-2,4-dienoic-acid) corresponds to a 2-hydroxymuconic sem-ialdehyde).

Focht and Williams [1'ring opening of p-toluenei

Cain et al. [20, 21 andand short-chain alkylbeminto 3-alkylpyrocatechol.chal (Fig.8). This catabcsulphate liberation before

)] detected the same pathway forrnlphonate (Fig.7).

22] found that benzenesulphonate:enesulphonates are not converted

but instead into 4-alkylpyrocate-Jism likewise includes prematurering opening.

Wickbold [10], Steber [8] and Schoberl and Kunkel [17] de-

tected sulphonated aliphatic LAS catabolites in the dis-

charges from OECD confirmatory test apparatuses. These

findings are in disagreement with desulphonation preceding

ring opening. Although Focht and Williams [19] favour desul-

phonation before ring opening, the ring opening mechanism

proposed by them appears to us to be more probable.

On the basis of the findings published by Baggi [18] and

by Focht and Williams. we have outlined a possible catabo-

lism pathway, shown below (Figs.9 and 10).

The ring-opening mechanism pro-posed in Fig.9 corresponds to that

found by Focht and Williams for p-tolu-3-CHz-CH-ICHz).-CH3 enesulphonate. Although the degrada-

~ tion shown schematicaUy in Fig.10 for

y l3-oxidation of the now aliphatic

S03Na' molecule has not been confirmed

~ 2NAD,HzO,Oz,CoAS}i experimentaUy, it probably, by analogy,

2NADH H D 2[HI represents the degradation mechanismz~ z ' predominating in nature.

...CH3-CHz-CH-ICHVa-C",9 SCoA v, ~

S03Na'r- 4FAD,4NAD,4HzO 4CoASH

~'-- 4FADHz, 4NADHz, 4Acetyl-SCoA

...°CH3-CHz-CH-C",9 SCoA v, ~

S03Na'11 t d' t ' F 2XH zlhydroxylaseJ,20zn erme la e:

cyclic peroxidel 2X(oxid, hydroxylasel, 2HzO, CoASH

...°CH3 -CH z-CH-C'OH

2,3-dihydroxy-4-9=sulphophenylbutyric v OH

acid ~ OH

S03Na'F 20z, 2YHz, (oxygenase)

2Y (oxidized oxygenasel,2HzO

2-hydroxy-3-sulphonato- O6-keto- 7 -ethyl-2,4- CH3-CHz-CH-C~octadiene-1,8-dioic acid I OH

C~O 'H-C/ COOH

11 I

H-C C-OH'c'"1

S03Na'

Fig.9. Pathway 01 biochemical alkylbenzenesulphonate oxidation (including ring

opening)

Tenside Surfactants Detergents 26 (1989) 2

Pathway ofbiochemical CH

alkylbenzenesulphonateoxidation

(including ring opening)

(Intermediates:1 sulphophenyl alcohol2 sulphophenyl alde-

hydel

4 Distance principie

Swisher et al. [23] and Wickbold [24]have independently found that the LAScomponents that are biodegraded mostrapidly are those which one methylgroup is the farthest from the sul-phophenyl configuration (Table 6).Thus, of the 2-sulphophenylalkanes, forexample, the tridecyl compound, whichcontains a C¡¡-alkyl on the tertiary car-bon atom, is degraded best (96 % de-crease in MBAS). In contrast, the 5-sul-phophenyldecane compound is de-graded worst (52% decrease in MBAS).

The obvious explanation for thisphenomenon, which Swisher called thedistance principIe, is based on sterichindrance of enzymatic conversion ofLAS by the aromatic molecular frac-tion. We have seen that linear alkylben-zenesulphonates are oxidized by ro-oxi-dation to form sulphophenyl alcohol,aldehyde and carboxylic acid before al-kyl chain shortening. The only catabo-lites of these first oxidation steps to beisolated and identified analyticallywere the sulphophenylcarboxylic acids.

.

-Ring splittlng

91

Accumulation of sulphophenylcarboxylic acids containing abenzene ring in the middle of the alkyl chain and having theoriginal LAS alkyl chain length did not occur.

Compared with the original surfactant molecule, the fattyacids isolated generally have an alkyl chain containing sever-al carbon atoms less.

Schoberl and Kunkel [17] have identified acids containingon average 4-5 carbon atoms, and Divo and Cardini[16] haveisolated carboxylic acids having an average of five carbonatoms. These findings show that, if the theory of steric hin-drance is correct, carboxylic acid degradation (j3-oxidation,elimination of acetyl coenzyme A units) is not atTected. Thehindrance must accordingly occur at an earlier stage.

Since neither carboxylic acids having the original numberof carbon atoms nor sulphophenyl aldehydes and alcoholsaccumulate in the culture medium, we can assume that ca-tabolism occurs rapidly and without hindrance after oxygenincorporation has taken place (hydroxylation of the surfact-ant molecule on a terminal CH) group of the alkyl chain).This means that only the first oxidation step, the hydroxyla-tion, is sterically hindered.

Van Ravenswaay and van der Linden [25] have foundexperimentally that steric etTects cause hydrocarbon

CH]

:",0Pathwayofbiochemical

alkylbenzenesulphonateoxidation(after ring splitting)

H-(11

H-(.OOH~-OH

~O3Na'-CoASH. 2!H)

-NaHSO~ (~p~1

,..0CH] -CH2-CH-C

'OHIC~O ..o

H~/ ~'\.SCoASHHC, ~C-OH

-NAO, H20, CoASH~O-NAOH¡,CH¡OH-C"OH

'H ,0 --(I 'OH

hydroxylation by a Pseudomonas aernginosa strain to be sub-strate-specific. They were able to show that the active centreof the responsible hydrocarbon hydroxylase is in the interiorofthe molecule since substrate hydrocarbon molecules (alky-lated benzene or cyclohexane derivatives) must have a veryparticular sterical size so as to be able to be bound to the ac-tive centre of the enzyme. From molecular measurements,the authors were able to determine the spatial extent of thecleft in the enzyme surface leading to this active centre. It hasa depth and width of approximately 8 A and 5 A respectively.

We tested whether the distance principIe may be attriQut-able to the same cause as follows:

As already stated, the MBAS analysis used for deterrnina-tion of the extent of degradation of anionic surfactants isspecific to the substance class. Wickbold [10] was able toshow that the compounds detected during degradationstudies of a-surfactants (OECD confirmatory test) using themethylene blue method were exlusively biochemically unaf-fected surfactant molecules, and that no alcoholic compo-nents were presento It can therefore be assumed that theMBAS analysis of LAS catabolites throws light on whetheralkyl chain hydroxylation has taken place on the LAS mole-cule or noto Under this premise, the degradation data deter-

mined by Wickbold. [24] for the 20 prin-cipal components of Marlon A (Ta-ble 6) can be used to calculate howlong the non-sulphophenylsubstitutedalkyl chain fraction must be so that therelevant LAS component can be hy-droxylated without hindrance [26].

Figure 11 shows that the ring-free al-I kyl chain side of the LAS must contain

at least seven carbon atoms in arder toensure unhindered hydroxylation. Iffewer carbon atoms are present, the de-gree of hydroxylation decreases signifi-cantly.

Molecular model measurements givea mean length of approximately 9 A

(glycolic and a diameter of approximately 2.5 Aacidl. CoASH for the C7-alkyl chain. The width of the

I molecule at the tertiary carbon-atom ofGlyoxylate the LAS is approximately 7 A. Assum-cycle ing that the active hydrophobic centre

of the enzyme LAS-alkyl hydroxylase isat the bottom of a cleft in the enzymesurface and that the enzyme cleft is

1I 8-9A deep, 7-8A broad and <7 Ahigh, LAS isomers containing non-sul-phophenyl-substituted alkyl chain endshaving fewer than seven carbon atomscan only be hydroxylated if the sul-phophenyl ring can algo enter the en-zyme cleft in a very specific spatial ar-

rangement.\ It can be stated for sure that the lim-

itations on the only steric molecular' configuration have a limiting effect on

l"'~-'2 the reaction rateo Since a change in theenzyme configuration may algo be nec-

,: ::-.\) essary, the hydroxylation rate mustdrop in accordance with the fallingnumber of sulphophenyl radical-freecarbon atoms of the alkyl chain end tobe hydroxylated. At the same time, this

~ theory, which explains the phenomenon

_c~O

4-keto-5-ethyl-2hexadiene-1.6 -dioicacid

,:H3-CHZ-CH-C"'O

I 'OH2-keto-3-ethylbutane-1.I.-dioicacid

,(...0'OH,¿.'

r FAD,NAD,HzD,CoASH

t- FADHz, NADHz, CH3-CHZ-CHZ-C~Oo o

C SCo/. HO~C-C~SCOA r- FAD,NAD,HzO (oASH

FADH. NADH

-Acetyl-SCoA .',o,-HzO 2CH3-C,SCoA ("(etv'-~LOJ.

o~ 4'0C-C-CH,

HO/

.,0

."'S(oA

(activated oxalacetic acid)

Fig.l0. Pathway 01 biochemical alkylbenzenesulphonate oxidation (alter ring splitting

Tenside Surfactants Detergents 26 (1989) 292

H-[11

H-[, ¿O[9'."'SCoA

~ NAO, H2O, CoASH (w-Carboxyl group

t--- NADH2, Acetyl-SCoA

Table 6. Individual biodegradation o/ the various C¡o-CirLAS isomers

LAS froro

5-Phenyldecane

[%] Degradation

52

LAS from

6-Phenydodecane[Ojo] Degradation

81C4-C-C5 CS-C-C6I

0~

C4-<;:'-C,4-Phenyldecane

0r

C3-<;:-4 68 5-Phenyldodecane 8901:

C2-C-C7I

01:

C¡-C-CS,

01:

C3-~-C83-Phenyldecane 92 4-Phenyldodecane 94

0r

C2-C-42-Phenyldecane 96 3-Phenyldodecane 94

0L 01:

C¡-C-CI0I

01:

2-Phenyldodecane 95

6-Phenylundecane 58 7-Phenyltricane C6-C-4I

01:

CS-C-C792

S-Phenyiundecane 72 6- Phenyltridecane

0~

C4-C-CS4-Phenylundecane

c;-c-csI

0~

C4-C-C6I

0~

CJ-9-C7 88 5-Phenyltridecane 93

01:

C2-<;:-CS

0~

C3-C-43-Phenylundecane 92 4- Phenyltridecane 94

0~

C¡-C-Cq2-Phenylundecane 95 3-Phenylundecane

0¿

C2-~-C10 95

0L 01:

0>: = o-phenylsulphonic acid group

of the distance principIe, makes it clear that, in principIe, allLAS isomers are biodegradable. Our own investigations ofthe degradation of 5-phenyldecanesulphonate [27] confirmnot only the assumption that the various LAS isomers areconverted by the same hydroxylase system, but also clearlyshow that this compound is hydroxylated just as rapidly asthe species containing a benzene ring inserted more or less in

the terminal position if a sufficient number of adapted LAS-degrading bacteria are present and if the concentration of5-phenyldecanesulphonate is sufficiently high (for example10-20 mg/l) (Figs.12 and 13).

In conclusion, it may be stated that our knowledge of mi-crobial catabolism of LAS is considerable. Although it has notbeen possible to provide experimental evidence of each indi-

~!.-c:o

:¡:IV

"CIV

50OJ

"C

V1..:m~

B

,Jr-\} ~,Sulphonated 5-phenyldecane (10 mg/l)

+ Harlon A@ (10 mg/l)

100

80

60

40

20

O

A

Sulphonated 5-Phenyldecane

(20 mg/l)r---~

c=.~

":ü"O..5.al

"O

V1<C'"E

I

.1

I '/IV /

"

J4 5 6 7 8 9 10

Number of ( atoms of the longer

linear alkyl chain part of a ('O-(13-LAS

Fig. 11. Dependency o/ M BAS degradation(%) on the C number o/ the longer linear alkylchain part o/ a Clo-CI3-LAS

o 10 20 30 40 50 60 70Oays -Fig. 12. Degradation 01 suiphonated 5-phenyldecane (A) and a combination 015-phenyldecane-sulphonate and MarloTi!> A (B) as a lunction 01 time without further influencing the activatedsludge

Tenside Surfactants Detergents 26 (1989) 2 93

Reprasentative Probenteilung van Suspensionen

A B

100

80

60

40

20

~c~":ü"C'"5-al

"C

VI<IX)~ Fig.13. Degradation of Marlo~ A (A) and

sulphonated 5-phenyldecane (8) as afunctionof time without further inj1uencing the activat-

ed sludge

70o 10 20 30Days -

40 50 60

vidual degradation step, it must be concluded that no biologi-cally stable catabolites are produced in the course of the nu-merous biochemical reactions on the LAS molecule. The endproducts of the reactions are carbon dioxide, water and sul-phate. This applies to alI ring position isomers. Due to stericfactors, however, not alI the isomers undergo the individualsteps at the same rateo

AlI this only applies to aerobic LAS degradations. Anaer-obicalIy, LAS is presumably converted only to an insignifi-cant extent, if at alI, and at a very low rateo To date, we haveencountered no findings which contradict this.

References

12. Huddleston, R. L. and Allred, R. C.: Dev. Ind. Microbiol. 4 (1963)24.

13. Heymann, J. J. and Molo/, A. H.: Water PolI. Control Federation39 (1967) 50.

14. Swisher, R. D.: J. Water PolI. Control Federation 35(1963) 1557.15. Baggi, G., Catelani, D., Colombi, A., Galli, E. and Treccani, 11::

Ann. Microbiol. Enzimol. 24 (1974) 317.16. Divo, C. and Cardini, G.: Tenside Detergents 17 (1980) 30.17. Schoberl, P. and Kunkel, E.:Tenside Detergents 14(1977) 293.18. Baggi, G., Catelani, D., Galli, E. and Treccani, 11:: Biochem. J.

126(1972) 1091.19. Focht, D. D. and Williams, F. D.: Can. J. Microbiol. 16 (1970)

309.20. Cain, R. B. and Farr, D. R.: Biochem. J. 106 (1968) 859.21. Bird, J. A. and Cain, R. B.: Biochem. J. 140(1974) 121.22. Johnston, J. B., Murray, K. and Cain, R. B.: A van Leeuvenhoek

41 (1975) 493.23. Swisher, R. D., Gledhill, w: E., Kimerle, R. A. and Taulli, 7: A.:

Proc. of the Vllth International Congress on Surface Active Sub-stances 4 (1978) 218.

24. Wickbold, R.: Tenside Detergents 12(1975) 25.25. Ravenswaay, J. C. and van der Linden, A. C.: A. van Leeuven-

hoek 37 (1971) 339.26. Schoberl, P. and Bock, K. J.: Tenside Detergents 17(1980) 17.27. Schoberl, P.: Tenside Detergents 16 (1979) 146.

The author of this contribution

Dr. P. Schoberl was born 28.12.37 in Annaberg/Erzgebirge; Abitur:1957 Gymnasium Hamburg-Harburg, University attendance until1966. Main subjects Biology and Microbiology. PhD in 1966. From1966-1968 assistence professor in the faculty of Microbiology at theUniversity Hamburg. Since 1968 employed at Hüls AG, Mari, FRGin the division of environmental protection. Main subjects catabolicmechanisms in microbial systems. 1126A

1. Gerike, P. and Fischer, w: K.: Ecotoxicology and EnvironmentalSafety 3 (1979) 159.

2. Fischer. w: K. and Gerike. P.: Water Research 9 (1975) 1137.3. Swisher. R. D.: Surfactant Science Series, 2. Ed., Marcel Dekker

Inc. (1987).4. Ne/son, J. F., McKinney, R. E., McAteer, J. H. and Konecky, M.

S.: Dev. Ind. Microbiol. 2 (1961) 101.5. Gerike. P., Fischer, W. K.. and Ho/tmann, W:: Water Research 14

(1980) 753.6. Gerike, P. and Jasiak, W:: World Surf. Congr. 1 (1984) 195.7. Phi//ips, W. K.: Ph. D. Thesis, Memphis State Univ., Univ. Micro-

films 7901118 (1978).8. Steber. J.: Tenside Detergents 16 (1979) 5.9. Krüger, R.: Fette, Seifen, Anstrichmitel 66(1964) 217.

10. Wickbo/d, R.: Proceedings of the IVth International Congress onSurface Active Substances 4 (1964) 903.

11. Cain. R. B.. Wi//iats, A. J. and Bird, J.A.: Proc. Int. Biodeteriora-tion Congress VII (1972) 136.

oder Sedimentationsanalysen, zugeführtwerden. Filtrations- und Trocknungsvor-gange entfallen.

.Erh6hte Analysengenauigkeit: Durch denWegfall von Trocknungsprozessen wer-den Agglomerationen vermieden, die zueinem verfálschten Analysenergebnisführen.

.Kostengünstig: Die Modulbauweise derProbenteiler Typ PT und PTF erlaubt beiVerwendung entsprechender Zuteilsy-steme den Einsatz als Teiler für Flüssig-keiten und Feststoffe. 3084

Reprasentative Probenteilung von Suspensionen

Probenteiler für f1üssigkeiten Typ PTF(Werkfoto: Kurt Retsch GmbH & Co. KG, Haan,

Tenside Surfactants Detergents 26 (1989) 294

Die exakte und reprasentative Probenteilung stellt die wich-tigste Voraussetzung für ein zuverlassiges, reproduzierbaresAnalysenergebnis dar.

Feststoffe in Form van Suspensionen oder Ausgangspro-ben nach NaBmahlungen konnen im bewahrten ProbenteilerTyp PT unter Verwendung der Aufgabevorrichtung für Flüs-sigkeiten Typ DF 1 nun ebenfalls reprasentativ geteilt wer-den. Der Probenteiler für Flüssigkeiten Typ PTF teilt Men-gen bis 4000 mI mit einer max. Feststoff-KomgroBe van2,5 mm in 8 bzw. 2-4-16-32 etc. reprasentative Proben. ZurAufnahme der Proben dienen standardisierte Laborglasermit 50-250 oder 500 mI. Die qualitative Teilgenauigkeit be-tragt in Abhangigkeit van den spezifischen Materialeigen-schaften :t. 0,5% und entspricht damit den Ergebnissen van

Trockenteilungen.Weitere Vorteile: j

.Zeiterspamis: Die Proben konnen in flüssigem Zustand %;geteilt und sofort nachfolgenden Analysen, z. B. NaBsieb-