Heterologous expression of genes for bioconversion of xylose to xylonic acid in Corynebacterium glutamicum and optimization of the bioprocess

Abstract

In bacterial system, direct conversion of xylose to xylonic acid is mediated through NAD-dependent xylose dehydrogenase (xylB) and xylonolactonase (xylC) genes. Heterologous expression of these genes from Caulobacter crescentus into recombinant Corynebacterium glutamicum ATCC 13032 and C. glutamicum ATCC 31831 (with an innate pentose transporter, araE) resulted in an efficient bioconversion process to produce xylonic acid from xylose. Process parameters including the design of production medium was optimized using a statistical tool, Response Surface Methodology (RSM). Maximum xylonic acid of 56.32 g/L from 60 g/L xylose, i.e. about 76.67% of the maximum theoretical yield was obtained after 120 h fermentation from pure xylose with recombinant C. glutamicum ATCC 31831 containing the plasmid pVWEx1 xylB. Under the same condition, the production with recombinant C. glutamicum ATCC 13032 (with pVWEx1 xylB) was 50.66 g/L, i.e. 69% of the theoretical yield. There was no significant improvement in production with the simultaneous expression of xylB and xylC genes together indicating xylose dehydrogenase activity as one of the rate limiting factor in the bioconversion. Finally, proof of concept experiment in utilizing biomass derived pentose sugar, xylose, for xylonic acid production was also carried out and obtained 42.94 g/L xylonic acid from 60 g/L xylose. These results promise a significant value addition for the future bio refinery programs.

Engineering Zymomonas mobilis for the Production of Xylonic Acid from Sugarcane Bagasse Hydrolysate

“…The productivity achieved by ZMa BX in sugarcane bagasse hydrolysate is smaller than that encountered for an engineered E. coli strain, which was 1.52 g L −1 h −1 [49] when a corn cob hydrolysate was used as feedstock. A modified C. glutamicum strain using rice straw hydrolysate as feedstock was able to produce 42.94 g L −1 xylonic acid from 60 g L −1 xylose only after 120 h incubation [48]. However, Z. mobilis was able to convert all xylose available in the medium containing hydrolysate into xylonic acid, showing its potential as a platform for industrial production of this organic acid.…”

“…Bacteria such as E. coli and C. glutamicum were engineered to xylonic acid production as well. An E. coli strain expressing xylB from C. crescentus achieved a productivity of 1.09 g L −1 h −1 [32], and strains of C. glutamicum expressing the same gene achieved productivities of 1.02 g L −1 h −1 [34] and 0.93 g L −1 h −1 [48]. A similar value (productivity of 1.8 g L −1 h −1 ) was also encountered for two E. coli strains engineered to produce xylonic acid [33,49].…”

Xylose Metabolism in Bacteria—Opportunities and Challenges towards Efficient Lignocellulosic Biomass-Based Biorefineries

“…Besides E. coli, C. glutamicum was also modified to enhance xylonic acid production [136]. In this strain, the deletion of the transcriptional repressor gene iolR, together with the expression of the xylose uptake IolT transporter, improved xylose uptake, cell growth, and the sugar conversion into xylonate [137].…”

Recent Progress on Chemical Production From Non-food Renewable Feedstocks Using Corynebacterium glutamicum

“…Currently, two transmembrane proteins capable of transporting xylose, XylE (Yim et al, 2016) and AraE (Chen Z. et al, 2017), are applied to boost xylose utilization, which promotes the accumulation of metabolites. C. glutamicum ATCC 31831, possessing the endogenic arabinose transporter AraE, and C. glutamicum ATCC 13032, which lacks this transporter, were simultaneously modulated to produce xylonic acid from xylose; as a result, engineered C. glutamicum ATCC 31831 produced approximately 10% more xylonic acid than engineered C. glutamicum ATCC 13032 (Sundar et al, 2020). During 120 h of fermentation, 75% xylose consumption in the engineered C. glutamicum ATCC 31831 strain likewise outstripped the 60% xylose consumption observed in the AraE-absent C. glutamicum ATCC 13032 strain.…”