Enhanced cellulase recovery without β‐glucosidase supplementation for cellulosic ethanol production using an engineered strain and surfactant. Issue 3 (10th October 2016)

• Record Type: Journal Article
• Authors: Huang, Renliang; Guo, Hong; Su, Rongxin; Qi, Wei; He, Zhimin
• Is Part Of: Biotechnology and bioengineering. Volume 114:Issue 3(2017)
• Page Start: 543
• Page End: 551
• Publication Date: 2016-10-10
• Subjects: lignocellulose -- cellulases -- β‐glucosidase -- recycling -- engineered strain -- surfactant; Biotechnology -- Periodicals; Bioengineering -- Periodicals; 660.6
• DOI: 10.1002/bit.26194
• Languages: English
• ISSNs: 0006-3592

Abstract

ABSTRACT: Recycling cellulases by substrate adsorption is a promising strategy for reducing the enzyme cost of cellulosic ethanol production. However, β‐glucosidase has no carbohydrate‐binding module (CBM). Thus, additional enzymes are required in each cycle to achieve a high ethanol yield. In this study, we report a new method of recycling cellulases without β‐glucosidase supplementation using lignocellulosic substrate, an engineered strain expressing β‐glucosidase and Tween 80. The cellulases and Tween 80 were added to an aqueous suspension of diluted sulfuric acid/ammonia‐treated corncobs in a simultaneous saccharification and fermentation (SSF) process for ethanol production. Subsequently, the addition of fresh pretreated corncobs to the fermentation liquor and remaining solid residue provided substrates with absorbed cellulases for the next SSF cycle. This method provided excellent ethanol production in three successive SSF cycles without requiring the addition of new cellulases. For a 10% (w/v) solid loading, a cellulase dosage of 30 filter paper units (FPU)/g cellulose, 0.5% Tween 80, and 2 g/L of the engineered strain, approximately 90% of the initial ethanol concentration from the first SSF process was obtained in the next two SSF processes, with a total ethanol production of 306.27 g/kg corncobs and an enzyme productivity of 0.044 g/FPU. Tween 80 played an important role in enhancing cellulase recovery. This new enzyme recycling method is more efficient and practical than other reported methods. Biotechnol. Bioeng. 2017;114: 543–551. © 2016 Wiley Periodicals, Inc. Abstract : A simple and practical method for recycling cellulases was developed: cellulase absorption onto substrates was combined with the use of an engineered S. cerevisiae strain and surfactants. This method did not require β‐glucosidase supplementation and was demonstrated to provide excellent ethanol production in the three successive high solid SSF processes with high ethanol concentrations, recovery efficiency, and enzyme productivity. This method is better than other known cellulase recovery methods and has great potential for industrial application.