Unique glucose oxidation catalysis of Gluconobacter oxydans constitutes an efficient cellulosic gluconic acid fermentation free of inhibitory compounds disturbance

Toxic inhibitory compounds from lignocellulose pretreatment are the major obstacle to achieve high bioconversion efficiency in biorefinery fermentations. This study shows a unique glucose oxidation catalysis of Gluconobacter oxydans with its gluconic acid productivity free of inhibitor disturbance....

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Published in:	Biotechnology and bioengineering 2019-09, Vol.116 (9), p.2191-2199
Main Authors:	Zhou, Pingping, Yao, Ruimiao, Zhang, Hongsen, Bao, Jie
Format:	Article
Language:	eng
Subjects:	Alcohols Aldehydes Bioconversion Catalysis Deoxyribonucleic acid Disturbance DNA DNA chips DNA microarrays Electron transport Fermentation Gene expression Genes Gluconic acid Gluconobacter oxydans Glucose Glucose dehydrogenase inhibitor tolerance Inhibitors Lignocellulose membrane‐bound glucose dehydrogenase (mGDH) Microorganisms Oxidation oxidative fermentation Phenolic compounds Phenols Pretreatment Transcription
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Summary:	Toxic inhibitory compounds from lignocellulose pretreatment are the major obstacle to achieve high bioconversion efficiency in biorefinery fermentations. This study shows a unique glucose oxidation catalysis of Gluconobacter oxydans with its gluconic acid productivity free of inhibitor disturbance. The microbial experimentations and the transcriptome analysis revealed that both the activity of the membrane‐bound glucose dehydrogenase and the transcription level of the genes in periplasmic glucose oxidation respiratory chain of G. oxydans were essentially not affected in the presence of inhibitory compounds. G. oxydans also rapidly converted furan and phenolic aldehyde inhibitors into the less toxic alcohols or acids. The synergy of the robust periplasmic glucose oxidation and the rapid inhibitor conversion of G. oxydans significantly elevated the efficiency of the oxidative fermentation in lignocellulose hydrolysate. The corresponding genes responsible for the conversion of furan and phenolic aldehyde inhibitors were also mined by DNA microarrays. The synergistic mechanism of G. oxydans provided an important option of metabolic modification for enhancing inhibitor tolerance of general fermentation strains. Zhou et al. found a unique membrane‐bound glucose oxidation system in Gluconobacter oxydans, whose protein synthesis and enzyme activity are free of the disturbance of lignocellulose‐derived inhibitors. G. oxydans is also capable of the rapid inhibitor conversion. The combination of the robust catalysis and inhibitor conversion of G. oxydans leads to a high oxidative efficiency of lignocellulose‐derived sugars to the corresponding sugar acids.
ISSN:	0006-3592 1097-0290