Ethanol production from xylose in engineered Saccharomyces cerevisiae strains: current state and perspectives

Abstract

Bioethanol production from xylose is important for utilization of lignocellulosic biomass as raw materials. The research on yeast conversion of xylose to ethanol has been intensively studied especially for genetically engineered Saccharomyces cerevisiae during the last 20 years. S. cerevisiae, which is a very safe microorganism that plays a traditional and major role in industrial bioethanol production, has several advantages due to its high ethanol productivity, as well as its high ethanol and inhibitor tolerance. However, this yeast cannot ferment xylose, which is the dominant pentose sugar in hydrolysates of lignocellulosic biomass. A number of different strategies have been applied to engineer yeasts capable of efficiently producing ethanol from xylose, including the introduction of initial xylose metabolism and xylose transport, changing the intracellular redox balance, and overexpression of xylulokinase and pentose phosphate pathways. In this review, recent progress with regard to these studies is discussed, focusing particularly on xylose-fermenting strains of S. cerevisiae. Recent studies using several promising approaches such as host strain selection and adaptation to obtain further improved xylose-utilizing S. cerevisiae are also addressed.

Enhanced biofuel production through coupled acetic acid and xylose consumption by engineered yeast

“…Engineered S. cerevisiae strains with the XR/XDH pathway grow extremely slowly when xylose serves as the sole carbon source under anaerobic conditions that are desirable for large-scale industrial fermentation 14,27,28 . We constructed an efficient xylose-fermenting S. cerevisiae strain SR8 by combining rational and combinatorial approaches 29 .…”

“…Therefore, metabolic engineering has been used to develop xylose-utilizing S. cerevisiae strains 7,14,15 by expression of nicotinamide adenine dinucleotide phosphate (NAD(P)H)-linked xylose reductase (XR) and nicotinamide adenine dinucleotide (NAD þ )-linked xylitol dehydrogenase (XDH) genes from Scheffersomyces stipitis; this pathway converts xylose to xylulose 14,16 , which can be metabolized via the pentosephosphate pathway after phosphorylation (Fig. 1).…”

Sequential Targeting of Xylose and Glucose Conversion in Fed-Batch Simultaneous Saccharification and Co-fermentation of Steam-Pretreated Wheat Straw for Improved Xylose Conversion to Ethanol

“…Improved tolerance to inhibitors and ability to convert xylose have been achieved by e.g., evolutionary engineering [12,13] and short-term adaptation during propagation [14]. However, xylose is still generally fermented by S. cerevisiae to ethanol at lower rates [15] and lower yields than glucose [15,16]. This has been attributed to capacity limitations in the pentose phosphate shunt [9] and mismatched co-factor dependency during xylose catabolism in engineered XR/XDHstrains [17].…”

Dynamic flux balance modeling of microbial co‐cultures for efficient batch fermentation of glucose and xylose mixtures

“…These metabolic engineering efforts have produced mixed results (Matsushika et al, 2009;Yomano et al, 2008) as complex and poorly understood regulatory mechanisms often counteract engineering strategies aimed at modifying cellular metabolism. Saccharomyces cerevisiae is widely used for the production of ethanol from glucose but this yeast does not have all the genes necessary for uptake and metabolism of pentose sugars.…”