Identification of candidate genes for yeast engineering to improve bioethanol production in very high gravity and lignocellulosic biomass industrial fermentations

Abstract

BackgroundThe optimization of industrial bioethanol production will depend on the rational design and manipulation of industrial strains to improve their robustness against the many stress factors affecting their performance during very high gravity (VHG) or lignocellulosic fermentations. In this study, a set of Saccharomyces cerevisiae genes found, through genome-wide screenings, to confer resistance to the simultaneous presence of different relevant stresses were identified as required for maximal fermentation performance under industrial conditions.ResultsChemogenomics data were used to identify eight genes whose expression confers simultaneous resistance to high concentrations of glucose, acetic acid and ethanol, chemical stresses relevant for VHG fermentations; and eleven genes conferring simultaneous resistance to stresses relevant during lignocellulosic fermentations. These eleven genes were identified based on two different sets: one with five genes granting simultaneous resistance to ethanol, acetic acid and furfural, and the other with six genes providing simultaneous resistance to ethanol, acetic acid and vanillin. The expression of Bud31 and Hpr1 was found to lead to the increase of both ethanol yield and fermentation rate, while Pho85, Vrp1 and Ygl024w expression is required for maximal ethanol production in VHG fermentations. Five genes, Erg2, Prs3, Rav1, Rpb4 and Vma8, were found to contribute to the maintenance of cell viability in wheat straw hydrolysate and/or the maximal fermentation rate of this substrate.ConclusionsThe identified genes stand as preferential targets for genetic engineering manipulation in order to generate more robust industrial strains, able to cope with the most significant fermentation stresses and, thus, to increase ethanol production rate and final ethanol titers.

Increased expression of the yeast multidrug resistance ABC transporter Pdr18 leads to increased ethanol tolerance and ethanol production in high gravity alcoholic fermentation

“…Despite being a laboratory medium, this medium is usually accepted as a good system to study high gravity fermentation conditions [29] leading to high ethanol production (up to 17 % (v/v)), most of which is produced by yeast cells in stationary-phase caused by the limitation of some nutrient other then glucose (Figure 4A). Interestingly, the PDR18 transcript levels, measured through RT-PCR, were found to be up-regulated progressively throughout the fermentation progression (Figure 4B).…”

Isolation of Saccharomyces cerevisiae from pineapple and orange and study of metal’s effectiveness on ethanol production

“…Moreover, previous studies reported that thermotolerant yeast can produce >6% ethanol within 24 h at 40 °C. From the result of the present study ( Tables 3 and 4), the isolates can be regarded as mild thermotolerant [46, 48]. …”

Vanillin Inhibits Translation and Induces Messenger Ribonucleoprotein (mRNP) Granule Formation in Saccharomyces cerevisiae: Application and Validation of High-Content, Image-Based Profiling

“…The non-essential deletion mutants exhibiting vanillin-sensitivity were classified into the functional categories “chromatin remodeling”, “vesicle transport” and “ergosterol biosynthetic process”, suggesting that these functions are important for vanillin tolerance. Another screening identified various vanillin-tolerant strains [8], [9]. A high-ergosterol-containing strain was more tolerant to vanillin, suggesting that high ergosterol content was responsible for vanillin tolerance [8].…”