Hoda Nouri, Tahere Sajadi, h, Mehrdad Azin *
Biological Journal of Microorganism, 6th Year, No. 22, Summer 2017, pp 1-13
2017
Introduction: Cellulose is the most abundant biopolymer in the world. Cellulase, including
endoglucanase, cellobiohydrolase and beta-glucosidase, catalyzes the hydrolysis of cellulose.
Released glucose from enzymatic hydrolysis of cellulosic biomass is used in different
biotechnology fields.
Materials and methods: In this study, seven different Trichoderma species were obtained from
Persian Type Culture Collection (PTCC) and in order to select the best ones, cellulase activity
of native strains was determined. Sodium salt of carboxymethyl cellulose (CMC-Na), Avicel
and cellobiose were used for endoglucanase, cellobiohydrolase (exoglucanase) and cellobiase
(beta-glucosidase) assays, respectively. Kinetics of cellulose production was evaluated for the
selected strain. Finally, random mutagenesis with 0.2 M sodium nitrate was done.
Results: Among 7 different fungal species, Trichoderma parceramosum PTCC 5140 was
selected as the best strain with the highest cellulase activity. This strain, by production of 0.182
U/ml of endoglucanase, 0.538 U/ml of exoglucanase and 0.109 U/ml of cellubiase, showed the
highest amount of all three constituents of cellulolytic complex. Random mutagenesis and
mutant selection of this strain caused to isolate 4 stable mutants that were able to produce 2 to
11 fold more enzymes compared with the parent strain.
Discussion and conclusion: Evaluation of cellulase production in mutant strains of
Trichoderma parceramosume PTCC 5140 showed that use of chemical mutagenesis with 2 to
11 fold increasing in enzyme activity is a potent method to improve cellulase complex activity.
In the current study, obtained mutant strains could be introduced as a potent cellulase producer
for further studies in bioconversion processes.