Increasing NADPH Availability for Xylitol Production via Pentose-Phosphate-Pathway Gene Overexpression and Embden–Meyerhof–Parnas-Pathway Gene Deletion in Escherichia coli

Abstract

Cofactor availability is often a rate-limiting factor in the bioconversion of xylose to xylitol. The overexpression of pentose phosphate pathway genes and the deletion of Embden–Meyerhof–Parnas pathway genes can modulate the glucose metabolic flux and increase the intracellular NADPH supply, enabling Escherichia coli cells to produce xylitol from corncob hydrolysates. The effects of zwf and/or gnd overexpression and pfkA, pfkB, and/or pgi deletion on the intracellular redox environment and xylitol production were examined. The NADPH-enhanced strain 2bpgi produced 162 g/L xylitol from corncob hydrolysates after a 76 h fed-batch fermentation in a 15 L bioreactor, which was 13.3% greater than the 143 g/L xylitol produced by the IS5-d control strain. Additionally, the xylitol productivity and xylitol yield per glucose for 2bpgi were 2.13 g/L/h and 2.50 g/g, respectively. Thus, the genetic modifications in 2bpgi significantly enhanced NADPH regeneration, making 2bpgi a potentially useful strain for the industrial-scale production of xylitol from detoxified corncob hydrolysates.

Production of Putrescine in Metabolic Engineering Corynebacterium crenatum by Mixed Sugar Fermentation

“…Next, the mixed sugar was used as carbon source to determine the production of putrescine by PC9 in the fermentation medium. However, the sugar composition of the hydrolysates prepared by different methods or feedstocks are various. − Then, the effect of mixed sugar was examined to see its optimal ratio with the total sugar concentration constant in the shake flask culture. As shown in Figure C, the optimum titer of 18.5 g/L putrescine was obtained by the sugar composition of glucose and xylose at a ratio of 3:1.…”

Microbial cell factories for bio-based biodegradable plastics production

“…Therefore, it can be applied in the synthesis of products with a higher degree of reduction and can be used to provide additional reducing power. 102 , 103 The ED pathway is widely distributed in Gram-negative bacteria. 104 Compared with the EMP pathway, the ED pathway converts glucose into pyruvate and glyceraldehyde-3-phosphate through only 4 reaction steps and can synthesize 1 molecule of NADPH instead of NADH.…”

Biosynthesis of value-added bioproducts from hemicellulose of biomass through microbial metabolic engineering

“…As NADPH availability is a rate-limiting factor in converting xylose to xylitol, through expressing genes of PP pathway and knocking-out Embden-Meyerhof-Parnas pathway genes in E.coli , the NADPH supply and xylitol production were increased. Compared with the control strain, xylitol production from corncob hydrolysates increased by 13.3% with the NADPH-enhanced strain ( Yuan et al, 2021 ). A xylose utilization pathway was engineered in cyanobacteria Synechocystis sp.…”