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Thermostable cellulases from the yeast trichosporon sp

Thermostable cellulases from the yeast trichosporon sp

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Saint anthony

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biology

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Thermostable Cellulases from the Yeast Trichosporon sp.

ABSTRACT

This study focuses on the identification of cellulolytic yeasts and the optimization of cellulase activities produced by

the best performing isolate among 30 cellulolytic yeast isolates. Enzymes produced from the Trichosporon genus

showed property to hydrolyze different substrates: carboxymethyl cellulose (CMC), cellulose fiber, and filter paper.

The optimum measured temperature was 55

C for CMCase and 60

C for FPase and optimal pH was found 5.0 for

CMCase and 4.0 to 6.0 for FPase. Cellulases produced by yeast are capable of hydrolyzing soluble and insoluble

substrates at elevated temperatures and at a wide pH range.

INTRODUCTION

Cellulose is the most important constituent of the plant cell wall [1]. This polymer is widely used in many industrial

sectors. Bioethanol made from cellulosic biomass attracts lots of attention as a biofuel, with economic advantages and

minimal impact on the environment. Bioethanol production requires four major steps: biomass pretreatment, cellulose

hydrolysis, fermentation, and distillation. It is achieved by a simultaneous action of three enzymes: endo-β-glucanase,

exo- β-glucanase, and β-glucosidase [2]. Fungi and bacteria are potential producers of cellulases enzymes. Yeast

cellulases gain interest, as they are active in a wide pH range and at high temperatures. Yeasts can produce thermo

stable cellulase, undenatured at temperatures greater than or equal to 70

C [3]. They can be used in the processes of

saccharifcation of lignocellulose into fermentable sugars for the production of bioethanol.

METHOD AND MATERIALS

• Cellulase producing yeast isolates were determined in Mandels and Weber medium (MW) based on CMC

as a unique carbon source.

• The molecular characterization was performed by carrying out sequencing of DNA ITS region.

• The MW medium was used for the production of these enzymes.

• The inoculum of the studied yeast was added to the culture medium. Cellulase activities were determined

by the dinitrosalicylic acid (DNS) method [4].

• The impact of temperature on the enzymes CMCase and FPase was evaluated at 4.8 pH and incubation at

different temperatures ranging from 20 to 100

C of the reaction mixtures.

• The kinetic of the enzymes was determined by measuring the concentration of glucose released during the

hydrolysis of the various substrates (CMC, FP) at incubation times ranging from 10 to 60 min.

RESULTS

• Isolation of yeasts resulted in a collection of 55 isolates, 30 of which were cellulosic. Among them,

Trichosporon sp exhibited CMCase, fiber cellulase, and FPase activity of 0.16 IU/mL, 0.09 IU/mL, and

0.07 IU/mL, respectively as shown in Fig 1.

• The enzymes produced are capable of hydrolyzing soluble CMC and insoluble cellulose.

• CMCase and FPase are active at temperatures ranging from 20 to 90

C, with optimal temperature at 55

as shown in Table 1.

• The cellulases activity of the yeast isolate has a wide pH range, ranging from 3.0 to 9.0.

• The CMCase reached a rate of 0.4 IU/mL at a concentration of 100 mg/mL of CMC and FPase activity

reached 0.1 IU/mL at 100 mg/mL of the filter paper.

• The amount of glucose during the hydrolysis of the filter paper was 4.14 mM, after 60 min of incubation.

• The activities of enzymes after optimization were three times higher for CMCase and five times with regard

to FPase and cellulase fiber.

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DISCUSSION

Fungi and bacteria are potential producers of cellulase enzymes. Yeast cellulases gain interest, as they are active in a

wide pH range and at high temperatures. Trichosporon laibachii yeast has CMCase activity, but unable to hydrolyze

insoluble substrates like cellulose fiber and filter paper [5]. Similar results are observed on fungi, as Lucas et al. [6]

detected no cellulase able to hydrolyze insoluble substrates. In our study CMCase and FPase are active at temperatures

ranging from 20 to 90

C, with optimal temperature at 55

C. In a similar work on fungi, such as Aspergillus niger and

Penicillium decumbens, the maximum CMCase activity was observed at 50

C [7]. Industrial processes for the

hydrolysis of cellulosic material into fermentable sugar are carried out under particular physical and chemical

conditions, at the optimum values of the activity of available commercial enzymes. The yeast enzymes of this study

are of considerable interest because of their activity at different temperatures and their ability to hydrolyze different

soluble and insoluble cellulosic substrates.

CONCLUSION

Trichosporon sp strain has a great potential to be used in the enzymatic saccharification of soluble CMC and insoluble

(cellulose fiber and filter paper) cellulosic substrates at a wide pH range, with an optimum at 5.0, and at high

temperatures of 55 to 70

ACKNOWLEDGEMENT

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Thermostable Cellulases from the Yeast Trichosporon sp. ABSTRACT This study focuses on the identification of cellulolytic yeasts and the optimization of cellulase activities produced by the best performing isolate among 30 cellulolytic yeast isolates. Enzymes produced from the Trichosporon genus showed property to hydrolyze different substrates: carboxymethyl cellulose (CMC), cellulose fiber, and filter paper. The optimum measured temperature was 55oC for CMCase and 60oC for FPase and optimal pH was found 5.0 for CMCase and 4.0 to 6.0 for FPase. Cellulases produced by yeast are capable of hydrolyzing soluble and insoluble substrates at elevated temperatures and at a wide pH range. INTRODUCTION Cellulose is the most important constituent of the plant cell wall [1]. This polymer is widely used in many industrial sectors. Bioethanol made from cellulosic biomass attracts lots of attention a ...
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Tags: bacteria microbiology Pathology Cyst Cellulase Yeast trichosporon