Unveiling the optimal parameters for cellulolytic characteristics of Talaromyces verruculosus SGMNPf3 and its secretory enzymes.

Abstract

Elucidation of different physico-chemical parameters and the secretory enzymes released by Talaromyces verruculosus SGMNPf3 during cellulosic biomass degradation. We determined the optimal pH, temperature and time course parameters for the efficient degradation of different natural and commercial cellulosic substrates by T. verruculosus SGMNPf3, previously isolated from a forest soil. The optimal growth of the fungus and production of its cellulases were obtained when the culture condition was maintained at pH 3·3 and temperature 30°C. Activity of the crude cellulases was maximum at 60°C. Activity of cellulase enzymes produced on natural cellulose substrates was higher than that on commercial cellulose substrates. A continuous increase in cellulase activity at different time points indicated no apparent end product inhibition. This might be attributed to the high individual cellulases, notably β-glucosidase (316·1 μmol g(-1) ) production. Zymogram of extracellular crude proteins showed two dominant extracellular protein bands of molecular weight 72·3 and 61·4 kDa, indicating their cellulolytic nature. MALDI-TOF and LC-MS/MS analysis of the 2DE spots also identified several enzymes including β-glucosidase involved in the process of cellulose degradation. Based on its optimal parameters for cellulolytic activities, we suggest that the fungus is acido-mesophilic. There was apparently no end-product inhibition of the cellulase activity and this is attributed to the ability of the fungus to produce sufficient β-glucosidase. The dominant proteins secreted by the fungus were confirmed to be cellulases. The high individual cellulase activities, better cellulase production on natural substrates and apparent absence of end-product inhibition are characteristics of T. verruculosus SGMNPf3 for use in harvesting naturally endowed energy in cellulosic biomass.