Improved ethanol production by a xylose-fermenting recombinant yeast strain constructed through a modified genome shuffling method

Abstract

BackgroundXylose is the second most abundant carbohydrate in the lignocellulosic biomass hydrolysate. The fermentation of xylose is essential for the bioconversion of lignocelluloses to fuels and chemicals. However the wild-type strains of Saccharomyces cerevisiae are unable to utilize xylose. Many efforts have been made to construct recombinant yeast strains to enhance xylose fermentation over the past few decades. Xylose fermentation remains challenging due to the complexity of lignocellulosic biomass hydrolysate. In this study, a modified genome shuffling method was developed to improve xylose fermentation by S. cerevisiae. Recombinant yeast strains were constructed by recursive DNA shuffling with the recombination of entire genome of P. stipitis with that of S. cerevisiae.ResultsAfter two rounds of genome shuffling and screening, one potential recombinant yeast strain ScF2 was obtained. It was able to utilize high concentration of xylose (100 g/L to 250 g/L xylose) and produced ethanol. The recombinant yeast ScF2 produced ethanol more rapidly than the naturally occurring xylose-fermenting yeast, P. stipitis, with improved ethanol titre and much more enhanced xylose tolerance.ConclusionThe modified genome shuffling method developed in this study was more effective and easier to operate than the traditional protoplast-fusion-based method. Recombinant yeast strain ScF2 obtained in this study was a promising candidate for industrial cellulosic ethanol production. In order to further enhance its xylose fermentation performance, ScF2 needs to be additionally improved by metabolic engineering and directed evolution.

The Coptotermes gestroi aldo–keto reductase: a multipurpose enzyme for biorefinery applications

“…Recently, several research groups have investigated the termite digestome, hypothesizing that auxiliary redox mechanisms may be involved in lignocellulose degradation [5, 26, 27, 32–34]. Among these studies, Scharf and Sethi [27] reported that an AKR acted synergically with termite and symbiotic GHs during pine wood hydrolysis.…”

“…The detoxification of hemicellulosic hydrolysates is of biotechnological interest, and many detoxification methods have been reported in the literature [9, 11, 14, 17, 32, 51]. Laccases and peroxidases are being applied in the development of enzymatic cocktails for detoxification of lignin components, consuming or generating ROS such as H 2 O 2 to remove soluble lignin in fermentation medium; thus, PAD enzymes such as Cg AKR-1 could also be applied for this purpose [10, 52, 53].…”

Production of Xylitol from d-Xylose by Overexpression of Xylose Reductase in Osmotolerant Yeast Candida glycerinogenes WL2002-5

“…Moreover, as a valuable synthetic building block, xylitol is one of the top 12 value-added materials produced from biomass, and thereby serves as a key economic driver of the biorefinery concept [7]. The major traits required of an industrial strain for fermenting lignocellulosic hydrolysate are efficient utilization of hexoses and pentoses, fast fermentation rates, high product yield and high tolerance of sugars, and fermentation inhibitors [3,8].…”

“…Xylose is the second most abundant sugar present in lignocellulosic biomass, after glucose [3]. Efficient fermentation of xylose is necessary to develop economically viable processes using lignocellulosic biomass [4].…”

Ethanol Production from Sugarcane Leaves by Kluyveromyces marxianus S1.17, a Genome-Shuffling Mediated Transformant

“…To improve the ability of K. marxianus to ferment xylose into ethanol, K. marxianus G2-16-1 was subjected to electroporation-mediated genome shuffling (Zhang and Geng 2012) using the chromosomal DNA of Pichia stipitis JCM 10742 T , a high-xylose fermenting yeast (Du Preez and Prior 1985) as the chromosomal donor. This study is the first report of genome shuffling between K. marxianus and P. stipitis.…”