The relation between xyr1 overexpression in Trichoderma harzianum and sugarcane bagasse saccharification performance.

This work investigates the influence of the positive regulator XYR1 of Trichoderma harzianum on the production of cellulolytic enzymes, using sugarcane bagasse as carbon source. Constitutive expression of xyr1 was achieved under the control of the strong Trichoderma reesei pki1 promoter. Five clones with xyr1 overexpression achieved higher xyr1 expression and greater enzymatic productivity when cultivated under submerged fermentation, hence validating the genetic construction for T. harzianum. Clone 5 presented a relative expression of xyr1 26-fold higher than the parent strain and exhibited 66, 37, and 36% higher values for filter paper activity, xylanase activity, and ß-glucosidase activity, respectively, during cultivation in a stirred-tank bioreactor. The overexpression of xyr1 in T. harzianum resulted in an enzymatic complex with significantly improved performance in sugarcane bagasse saccharification, with an enhancement of 25% in the first 24h. Our results also show that constitutive overexpression of xyr1 leads to the induction of several important players in biomass degradation at early (24h) and also late (48h) timepoints of inoculation. However, we also observed that the carbon catabolite repressor CRE1 was upregulated in xyr1 overexpression mutants. These findings demonstrate the feasibility of improving cellulase production by modifying regulator expression and suggest an attractive approach for increasing total cellulase productivity in T. harzianum.

Increased production of cellulases and xylanases by Penicillium echinulatum S1M29 in batch and fed-batch culture.

The development of more productive strains of microorganisms and processes that increase enzyme levels can contribute to the economically efficient production of second generation ethanol. To this end, cellulases and xylanases were produced with the S1M29 mutant strain of Penicillium echinulatum, using different concentrations of cellulose (20, 40, and 60 g L(-1)) in batch and fed-batch processes. The highest activities of FPase (8.3 U mL(-1)), endoglucanases (37.3 U mL(-1)), and xylanases (177 U mL(-1)) were obtained in fed-batch cultivation with 40 g L(-1) of cellulose. The P. echinulatum enzymatic broth and the commercial enzyme Cellic CTec2 were tested for hydrolysis of pretreated sugar cane bagasse. Maximum concentrations of glucose and xylose were achieved after 72 h of hydrolysis. Glucose yields of 28.0% and 27.0% were obtained using the P. echinulatum enzymatic extract and Cellic CTec2, respectively.