Abstract
Bioethanol is considered an excellent alternative to fossil fuels, since it importantly contributes to the reduced consumption of crude oil, and to the alleviation of environmental pollution. Up to now, the baker yeast Saccharomyces cerevisiae is the most common eukaryotic microorganism used in ethanol production. The inability of S. cerevisiae to grow on pentoses, however, hinders its effective growth on plant biomass hydrolysates, which contain large amounts of C5 and C12 sugars. The industrial-scale bioprocessing requires high temperature bioreactors, diverse carbon sources, and the high titer production of volatile compounds. These criteria indicate that the search for alternative microbes possessing useful traits that meet the required standards of bioethanol production is necessary. Compared to other yeasts, Kluyveromyces marxianus has several advantages over others, e.g., it could grow on a broad spectrum of substrates (C5, C6 and C12 sugars); tolerate high temperature, toxins, and a wide range of pH values; and produce volatile short-chain ester. K. marxianus also shows a high ethanol production rate at high temperature and is a Crabtree-negative species. These attributes make K. marxianus promising as an industrial host for the biosynthesis of biofuels and other valuable chemicals.
Highlights
Saccharomyces cerevisiae plays an extremely important role for millennia in food and beverage productions, and is the most studied yeast species [1]
This review aims to focus on the latest progress in Omics studies of K. marxianus, especially the recent transcriptomic and proteomic studies of K. marxianus grown on specific substrates (e.g., Jerusalem artichokes) or in stress conditions
S. cerevisiae immediately declined after glucose upshift, whereas the increase in oxygen uptake in such circumstances was recorded in K. marxianus, indicating the maintenance of respiratory activity in the Crabtree-negative yeast
Summary
Saccharomyces cerevisiae plays an extremely important role for millennia in food and beverage productions, and is the most studied yeast species [1]. In the study of Wang et al [12], various genes encoding fatty acid and ergosterol metabolism were downregulated under multiple inhibitors stress such as phenols, furfural, HMF, and acetic acid. These consistent findings might explain differences in ethanol tolerance capability between S. cerevisiae and K. marxianus. In 1995, Piper stated that many changes induced by ethanol stress were similar to those triggered by heat stress and the synergistic effects of heat and ethanol stresses were recorded [15] These present reports reconfirmed Piper’s statement as various genes related to central carbon metabolic pathways were found to exhibit the low expression levels upon heat or ethanol exposure (Table 1). Expressed genes (DEGs) analysis: Module 1: 230–130 mV–36 vs. 230–N–72
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