Development of an arabinose-fermenting Zymomonas mobilis strain by metabolic pathway engineering

Abstract

The substrate fermentation range of the ethanologenic bacterium Zymomonas mobilis was expanded to include the pentose sugar, L-arabinose, which is commonly found in agricultural residues and other lignocellulosic biomass. Five genes, encoding L-arabinose isomerase (araA), L-ribulokinase (araB), L-ribulose-5-phosphate-4-epimerase (araD), transaldolase (talB), and transketolase (tktA), were isolated from Escherichia coli and introduced into Z. mobilis under the control of constitutive promoters that permitted their expression even in the presence of glucose. The engineered strain grew on and produced ethanol from L-arabinose as a sole C source at 98% of the maximum theoretical ethanol yield, based on the amount of consumed sugar. This indicates that arabinose was metabolized almost exclusively to ethanol as the sole fermentation product, with little by-product formation. Although no diauxic growth pattern was evident, the microorganism preferentially utilized glucose before arabinose, apparently reflecting the specificity of the indigenous facilitated diffusion transport system. This microorganism may be useful, along with the previously developed xylose-fermenting Z. mobilis (M. Zhang, C. Eddy, K. Deanda, M. Finkelstein, and S. Picataggio, Science 267:240-243, 1995), in a mixed culture for efficient fermentation of the predominant hexose and pentose sugars in agricultural residues and other lignocellulosic feedstocks to ethanol.

High‐throughput sequencing reveals adaptation‐induced mutations in pentose‐fermenting strains of Zymomonas mobilis

“…Again, we found that improved xylose transport led to improved xylose fermentation performance, confirming our previous results. Previous reports have also predicted that sugar transport is a limiting factor in arabinose fermentations by Z. mobilis (Deanda et al, 1996). The Glf protein likely transports this sugar into the cell, but the affinity of Glf for arabinose is much lower than its affinity for other sugars, including glucose and xylose (Weisser et al, 1996).…”

Growth of engineered Pseudomonas putida KT2440 on glucose, xylose, and arabinose: Hemicellulose hydrolysates and their major sugars as sustainable carbon sources

“…Therefore, d-xylose is converted to d-xylulose 5-phosphate through d-xylulose (Gu et al, 2010;Kawaguchi et al, 2006). For the utilization of l-arabinose, a group of three genes, araB (ribulokinase), araA (l-arabinose isomerase), and araD (l-ribulose phosphate 4-epimerase), is necessary, which mediates the conversion of l-arabinose though l-ribulose and l-ribulose 5-phosphate to d-xylulose 5-phosphate (Deanda, Zhang, Eddy, & Picataggio, 1996;Xiong, Wang, & Chen, 2016). This araBAD operon has been successfully integrated and heterologously expressed in C. glutamicum (Kawaguchi, Sasaki, Vertès, Inui, & Yukawa, 2008) to enable its growth on l-arabinose.…”

Over-expression of xylulokinase in a xylose-metabolising recombinant strain ofZymomonas mobilis

“…Zymomonas mobilis is an attractive ethanologen for cost-competitive ethanol production in view of its high ethanol yield, rapid specific substrate uptake rates and high ethanol tolerance. For conversion of lignocellulosic raw materials to ethanol, broadening its substrate range has been achieved successfully with introduction of exogenous genes from Escherichia coli encoding the assimilation and metabolism of the pentose sugars xylose and arabinose [1,2]. Kinetic studies on these recombinant strains using either xylose or glucose/xylose media have established that the specific rates of xylose uptake were 2-3-fold lower than those for glucose [3][4][5][6][7].…”