title: Enhanced cellulase recovery without β-glucosidase supplementation for cellulosic ethanol production using an engineered strain and surfactant.
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.
authors.affiliation: Tianjin Engineering Center of Bio Gas/Oil Technology, School of Environmental Science and Engineering, Tianjin University, Tianjin, China.
authors.forename: Renliang
authors.initials: R
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.|Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin, China.|Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, China.
authors.forename: Rongxin
authors.initials: R
authors.lastname: Su
authors.affiliation: State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.|Tianjin Key Laboratory of Membrane Science and Desalination Technology, Tianjin University, Tianjin, China.|Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Qi
authors.affiliation: State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
authors.forename: Zhimin
authors.initials: Z
authors.lastname: He
mesh_terms: D056804:Biofuels; D002480:Cellulase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism*; D000431:Ethanol / Q000032:analysis / Q000378:metabolism*; D005285:Fermentation; D060847:Metabolic Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013501:Surface-Active Agents / Q000737:chemistry; D003313:Zea mays / Q000737:chemistry; D001617:beta-Glucosidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D056804:Biofuels; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D013501:Surface-Active Agents; D000431:Ethanol; D002482:Cellulose; D001617:beta-Glucosidase; D002480:Cellulase
keywords: cellulases; engineered strain; lignocellulose; recycling; surfactant; β-glucosidase