title: Improving volatile fatty acids production by exploiting the residual substrates in post-fermented sludge: Protease catalysis of refractory protein.
abstract: The real cause to the low yield of volatile fatty acids (VFAs), from inhibition or low biodegradation, is uncertain in sludge anaerobic fermentation. In this study, poor biodegradability of proteins and fast decrease of the indigenous hydrolase activity in the residual post-fermented sludge were found to be the major reasons. With the addition of trypsin or alkaline protease in residual post-fermented sludge after primary alkaline fermentation, degradation efficiency of refractory protein increased by 33.6% and 34.8%, respectively. Accordingly, the VFAs yields were improved by 69.7% and 106.1%, respectively. Furthermore, the activities of added trypsin and alkaline protease could maintain at 13.52 U/mL and 19.11 U/mL in the alkaline fermentation process. This study demonstrated that exploiting the refractory proteins in residual post-fermented sludge by protease addition seems to be a very promising way for improving VFAs yield of conventional alkaline fermentations with waste activated sludge.
authors.affiliation: School of Environmental and Civil Engineering, Jiangnan University, 214122 Wuxi, Jiangsu Province, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Yin
authors.affiliation: School of Environmental and Civil Engineering, Jiangnan University, 214122 Wuxi, Jiangsu Province, China; Jiangsu Key Laboratory of Anaerobic Biotechnology, 214122 Wuxi, Jiangsu Province, China; Jiangsu Coorperative Innovation Center of Technology and Material of Water Treatment, 215011 Suzhou, Jiangsu Province, China.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Liu
authors.affiliation: School of Environmental and Civil Engineering, Jiangnan University, 214122 Wuxi, Jiangsu Province, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: School of Environmental and Civil Engineering, Jiangnan University, 214122 Wuxi, Jiangsu Province, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Bai
authors.affiliation: School of Environmental and Civil Engineering, Jiangnan University, 214122 Wuxi, Jiangsu Province, China; Jiangsu Key Laboratory of Anaerobic Biotechnology, 214122 Wuxi, Jiangsu Province, China; Jiangsu Coorperative Innovation Center of Technology and Material of Water Treatment, 215011 Suzhou, Jiangsu Province, China. Electronic address: liuhe@jiangnan.edu.cn.
authors.forename: He
authors.initials: H
authors.lastname: Liu
authors.affiliation: School of Environmental and Civil Engineering, Jiangnan University, 214122 Wuxi, Jiangsu Province, China; Jiangsu Key Laboratory of Anaerobic Biotechnology, 214122 Wuxi, Jiangsu Province, China; Jiangsu Coorperative Innovation Center of Technology and Material of Water Treatment, 215011 Suzhou, Jiangsu Province, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Fu
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors; D002384:Catalysis; D010450:Endopeptidases / Q000378:metabolism*; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D005285:Fermentation; D012722:Sewage; D014357:Trypsin / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005232:Fatty Acids, Volatile; D012722:Sewage; D010450:Endopeptidases; D014357:Trypsin; C087822:alkaline protease
keywords: Alkaline fermentation; Protease; Residual substrate; Volatile fatty acids; Waste activated sludge