Prezentare Timisoara 2008

7/27/2019 Prezentare Timisoara 2008

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The efficient conversion of biomass was

performed in more steps, such as: chemical pre-

treatment, followed by a lignocelluloses

biopolymers hydrolysis to reducing sugars

(enzymatically or chemically), by alcoholicfermentation of reducing sugars, by distillation

and purification of bioethanol [4, 8, 9, 12, 17, 19].

The lignocelluloses biomass hydrolysis to

glucose, could be ecologically and economically

performed by a complex enzymatic system, mainly

formed by three types of hydrolases:endoglucanases, exoglucanases, -glycosidase,which act together, cutting the glicosydic

bonds [10, 14]. It was find out that the mixtures of

cellulases and amylases enhance the hydrolysis

efficiency. The productivity of hydrolysis is

influenced by several factors, but the mostimportant factors which are modelling the

hydrolysis process are as following: the pre-

treatment method, the substrate concentration,

the pre-treatment quality, the enzymes mixtures,

the temperature conditions, pH and the shaking

conditions [7, 15, 20].


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The goal of this research is the

testing of the efficiency of someenzymes and enzymatic mixtures,

used for the hydrolysis of three

lignocellulosic substrates, without

performing chemical pre-treatment.

AIM OF THE INVESTIGATIONS


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Three lignocelluloses substrates, have been

used such as:Miscanthus, maize stalk and wheatbran, which were ground (0,5 1 mm sieve

diameter), as standard routine for enzymatic

hydrolysis. The first step which has beenperformed was the laboratory analysis

concerning the % moisture content of the

substrates (The Practical Reference Method, SR

ISO 712/1999) [2].

After that, the lignocelluloses substrates

were hydrolysed using some commercial enzymepreparations: MethaPlus (-glucanase, xylanase,cellulase), Veron 191 (xylanase) and Hep C

(cellulase).

We also performed the hydrolysis of bran by

using enzymatic mixtures, which contained

Veron 393 (hemicellulase), Veron MX (xylanase)and amylases, namely: Veron M4 and BG -malt,because we will always find flour traces in wheat

bran (residual starch). The flour traces will

substantial enhances the reducing sugars

concentration, therefore the efficiency of

bioethanols production [3].

MATERIALS

AND

METHODS


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We used the enzymes

concentrations showed in their

technical specifications. Enzymatic

hydrolysis was performed at 550 C,during 20 h period, at pH=5,5, on a

rotary shaker at 200 rpm.

We performed all the experiments

in triplicate and presented them as

mean value. It was also prepared acontrol sample (without enzyme),

for each trial.

The efficiency of hydrolysis was

estimated by quantifying the

amount of reducing sugars. Thereducing sugars were determinated

as glucose, by reading the

absorption at 640 nm, using 3,5-

dinitrosalicilic (Peterson and

Porath modified method) [6, 18].


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Figure 1 emphasizes the differences between substrates, concerning the

efficiency of enzimatical hydrolysis, by using different enzymes.

0

5

10

15

20

25

30

35

40

Control MethaPlus Veron 191 Hep C

R

educingsugars%

Miscanthus

Maize stalk

Wheat bran

Figure 1. Increase of reducing sugars concentrationsafter enzymatic hydrolysis

The increasing of reducing sugars concentration, by enzimatical hydrolysis

using MethaPlus, in comparison to control, was as follows: 110.80 % to

Miscanthus, de 126.15 % to maize stalk and 118.76 % to wheat bran.

The increase of reducing sugars concentration, by enzimatical hydrolysis

using Veron 191, in comparison to control, was as follows: 99.30 % toMiscanthus, de 112.07 % to maize stalk and 79.20 % to wheat bran.


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All the enzymatic mixtures used for hydrolysis, enhanced its efficiency

(figure 2). Conclusively, reducing sugars concentration raised with

56.03 % by using Veron M4, with 49.27 % by using Veron 393, with

69.84 % by using BG -malt and with 53.57 % by using Veron MX, incomparison to the values obtained by using only MethaPlus (15,311%).

8.502

15.311

23.891

26.005

23.51422.856

0

5

10

15

20

25

30

Control

MethaPlus

MethaPlus+

amilaseVeron

M4

MethaPlus+

hemicelullase

Veron393

MethaPlus+

amilaseBG

alpha-malt

MethaPlus+

xylanase

VeronMX

Reducingsugars%

Figure 2. Increase of the reducing sugars concentrations after

hydrolysis with enzymatic mixtures


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In comparison to the control, the efficiency of hydrolysis was: 181.004

% for MethaPlus-Veron M4 mixture, 168.83 % for MethaPlus-Veron 393

mixture, 205.86 % for MethaPlus-BG -malt mixture and 176.57 % forMethaPlus-Veron MX mixture. It is easy to observe that the enzymatic

mixture which contains BG -malt was the most efficient, theproductivity of hydrolysis being superior to all others variants.

CONCLUSIONSThe results of the enzymatic hydrolysis of all

substrates emphasize the increase of reducing sugars

content, especially to the maize stalk, no matter the

enzyme used. These phenomena dues to the large content

of soluble sugars from maize stalk. The increase ofreducing sugars content for Miscanthus and wheat bran

is moderate.

MethaPlus was more active than Veron 191 and Hep C,

due to the fact that this product was already a commercial

enzymatic mixture.


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Prezentare Timisoara 2008