Feasibility studies with lignin blocking additives in enhancing saccharification and cellulase recovery: Mutant UV-8 of T. verruculosus IIPC 324 a case study

Abstract

The process economics of fermentable sugar production is dependent on the performance of cellulase cocktail on realistic lignocellulosic biomass and their capability to be recovered and recycled. Feasibility studies were conducted to enhance the digestibility of acid pretreated sugarcane bagasse using novel cellulase cocktail obtained from stable mutant UV-8 of Talaromyces verruculosus IIPC 324 in presence of lignin blocking additives. PEG 6000 was shortlisted as the best additive as it could simultaneously enhance saccharification and overall cellulase recoveries namely cellobiohydrolase, endoglucanase and cellobiase. Addition of 0.3 g PEG 6000/g acid-insoluble lignin content, resulted in 55% and 49.2% saccharification yields in terms of reducing sugars and glucose respectively using this cellulase cocktail (25 mg protein/g cellulose content) after 72 h from acid pretreated sugarcane bagasse loaded at 7.5%. The study also suggested that the endoglucanase of this mutant was unique with high desorption capability as 85% activity was observed in the saccharified broth devoid of any lignin blocking additive. At its optimum concentration, PEG 6000 was able to retain 94 ± 0.79% cellobiohydrolase I and 97.97 ± 1.16% cellobiase enzyme in the saccharified broth which were otherwise lost in residual biomass by ∼80%, in the absence of this polymeric additive. These results suggest that PEG 6000 was the most promising facilitator for recycling of cellulases obtained from mutant UV-8 of Talaromyces verruculosus IIPC 324 in particular. It paved a way towards the production of cheaper fermentable sugars which serve as a starting raw material for the production of green chemicals and fuels.