Increasing Ethanol Tolerance and Ethanol Production in an Industrial Fuel Ethanol Saccharomyces cerevisiae Strain

Abstract

The stress imposed by ethanol to Saccharomyces cerevisiae cells are one of the most challenging limiting factors in industrial fuel ethanol production. Consequently, the toxicity and tolerance to high ethanol concentrations has been the subject of extensive research, allowing the identification of several genes important for increasing the tolerance to this stress factor. However, most studies were performed with well-characterized laboratory strains, and how the results obtained with these strains work in industrial strains remains unknown. In the present work, we have tested three different strategies known to increase ethanol tolerance by laboratory strains in an industrial fuel–ethanol producing strain: the overexpression of the TRP1 or MSN2 genes, or the overexpression of a truncated version of the MSN2 gene. Our results show that the industrial CAT-1 strain tolerates up to 14% ethanol, and indeed the three strategies increased its tolerance to ethanol. When these strains were subjected to fermentations with high sugar content and cell recycle, simulating the industrial conditions used in Brazilian distilleries, only the strain with overexpression of the truncated MSN2 gene showed improved fermentation performance, allowing the production of 16% ethanol from 33% of total reducing sugars present in sugarcane molasses. Our results highlight the importance of testing genetic modifications in industrial yeast strains under industrial conditions in order to improve the production of industrial fuel ethanol by S. cerevisiae.

Diversity of fungi and dynamics of ethanol concentration during fermentation of porang (Amorphophallus oncophyllus)

“…At 72 hours of fermentation, diversity decreased because the substrate had been used, so there was only a little substrate left. Moreover, some toxic compounds as the results of metabolism, such as ethanol, can inhibit the growth of fungi (Pérez-Gallardo et al 2013;Rodrigues et al 2015;Varize et al 2022). The highest alcohol production at 48 hours of fermentation could inhibit the growth of fungi after 48 hours of fermentation.…”

Polyextremophile engineering: a review of organisms that push the limits of life

“…Fermentation of biofuels such as isobutanol or ethanol requires microbes tolerant of high product titer (Sardessai and Bhosle, 2004;Dunlop et al, 2011;Varize et al, 2022).…”

Optimal trade-off between boosted tolerance and growth fitness during adaptive evolution of yeast to ethanol shocks

“…Therefore, the main challenge of genetic screenings and ALE schemes is isolating stress-resistant yeasts strains that exhibit good growth and fermentation performance [7,17,19,23].…”

“…Adaptation to severe stresses is even more prone to trade-off effects associated with low growth fitness; cells tend to reallocate energy resources, normally used for propagation, to overcome a life-threatening condition [20–22]. Therefore, the main challenge of genetic screenings and ALE schemes is isolating stress-resistant yeasts strains that exhibit good growth and fermentation performance [7, 17, 19, 23].…”