Image_2_Expression and Characteristics of Two Glucose-Tolerant GH1 β-glucosidases From Actinomadura amylolytica YIM 77502T for Promoting Cellulose Deg.JPEG (1.49 MB)

Image_2_Expression and Characteristics of Two Glucose-Tolerant GH1 β-glucosidases From Actinomadura amylolytica YIM 77502T for Promoting Cellulose Degradation.JPEG

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posted on 18.12.2018 by Yi-Rui Yin, Peng Sang, Wen-Dong Xian, Xin Li, Jian-Yu Jiao, Lan Liu, Wael N. Hozzein, Min Xiao, Wen-Jun Li

The bioconversion of lignocellulose in various industrial processes, such as biofuel production, requires the degradation of cellulose. Actinomadura amylolytica YIM 77502T is an aerobic, Gram-positive actinomycete that can efficiently degrade crystalline cellulose by extracellular cellulases. Genomic analysis of A. amylolytica identified 9 cellulase and 11 β-glucosidase genes that could potentially encode proteins that digest cellulose. Extracellular proteome characterization of A. amylolytica cell-free culture supernatant by liquid chromatography tandem mass spectrometry analysis revealed that 4 of these cellulases and 2 of these β-glucosidases functioned during cellulose hydrolysis. Thin-layer chromatography analysis revealed extracellular β-glucosidases play a major role in carboxyl methyl cellulose (CMC) degradation of products in culture supernatants. In this study, 2 of the identified secreted β-glucosidases, AaBGL1 and AaBGL2, were functionally expressed in Escherichia coli and found to have β-glucosidase activity with wide substrate specificities, including for p-nitrophenyl β-D-glucopyranoside (pNPG), p-nitrophenyl-beta-D-cellobioside (pNPC), and cellobiose. Moreover, AaBGL1 and AaBGL2 had high tolerances for glucose. After adding these β-glucosidases to commercial cellulases, the degradation rates of CMC, Avicel, birch sawdust, and corncob powder increased by 37, 42, 33, and 9%, respectively. Overall, this work identifies an alternative potential source of β-glucosidases with potential applications in commercial cellulose utilization and the bioenergy industry.

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