Advances in yeast alcoholic fermentations for the production of bioethanol, beer and wine

Eliodório, Kevy Pontes; Cunha, Gabriel Caetano de Góis e; Müller, Caroline; Lucaroni, Ana Carolina; Giudici, Reinaldo; Walker, Graeme M.; Alves, Sérgio L.; Basso, Thiago Olitta

doi:10.1016/bs.aambs.2019.10.002

Cited by 42 publications

(28 citation statements)

References 167 publications

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“…1 ). While the optimal temperature for the cellulase cocktail we used is between 50 and 65 °C [ 48 ], the emulsions still reach nearly 80% conversion in 48 h at temperatures as low as 30 °C, which is the preferred temperature for non-thermotolerant yeasts like Saccharomyces cerevisiae [ 35 ]. The hydrolysis rate improves substantially when the temperature is increased to 42 °C, at which 80% conversion of the emulsion is reached in only 3 h. At the highest temperature examined, 50 °C, nearly full conversion of the emulsion is achieved within 12 h, while the MCC remains incompletely hydrolyzed even after 2 days.…”

Section: Resultsmentioning

confidence: 99%

“…Two thermotolerant yeasts that are well-suited for this application include Kluyveromyces marxianus [ 29 – 31 ] and Ogataea ( Hansenula ) polymorpha [ 32 , 33 ], both of which can naturally ferment glucose into ethanol at high yields. These yeasts broaden the range of possible temperatures for the SSF process, as they can both ferment at up to 50 °C [ 29 , 30 , 33 , 34 ], whereas the optimal temperature for Saccharomyces cerevisiae is only 30 °C [ 35 , 36 ]. While both of these thermotolerant yeasts have been previously studied for their use in biofuel production, there is yet to be a three-way direct comparison of ethanol production between S. cerevisiae , O. polymorpha , and K. marxianus , and the use of O. polymorpha in an SSF process has not been reported.…”

Section: Introductionmentioning

confidence: 99%

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Cellulosic biofuel production using emulsified simultaneous saccharification and fermentation (eSSF) with conventional and thermotolerant yeasts

Hoffman

Álvarez

Alfassi

et al. 2021

Biotechnol Biofuels

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Background Future expansion of corn-derived ethanol raises concerns of sustainability and competition with the food industry. Therefore, cellulosic biofuels derived from agricultural waste and dedicated energy crops are necessary. To date, slow and incomplete saccharification as well as high enzyme costs have hindered the economic viability of cellulosic biofuels, and while approaches like simultaneous saccharification and fermentation (SSF) and the use of thermotolerant microorganisms can enhance production, further improvements are needed. Cellulosic emulsions have been shown to enhance saccharification by increasing enzyme contact with cellulose fibers. In this study, we use these emulsions to develop an emulsified SSF (eSSF) process for rapid and efficient cellulosic biofuel production and make a direct three-way comparison of ethanol production between S. cerevisiae, O. polymorpha, and K. marxianus in glucose and cellulosic media at different temperatures. Results In this work, we show that cellulosic emulsions hydrolyze rapidly at temperatures tolerable to yeast, reaching up to 40-fold higher conversion in the first hour compared to microcrystalline cellulose (MCC). To evaluate suitable conditions for the eSSF process, we explored the upper temperature limits for the thermotolerant yeasts Kluyveromyces marxianus and Ogataea polymorpha, as well as Saccharomyces cerevisiae, and observed robust fermentation at up to 46, 50, and 42 °C for each yeast, respectively. We show that the eSSF process reaches high ethanol titers in short processing times, and produces close to theoretical yields at temperatures as low as 30 °C. Finally, we demonstrate the transferability of the eSSF technology to other products by producing the advanced biofuel isobutanol in a light-controlled eSSF using optogenetic regulators, resulting in up to fourfold higher titers relative to MCC SSF. Conclusions The eSSF process addresses the main challenges of cellulosic biofuel production by increasing saccharification rate at temperatures tolerable to yeast. The rapid hydrolysis of these emulsions at low temperatures permits fermentation using non-thermotolerant yeasts, short processing times, low enzyme loads, and makes it possible to extend the process to chemicals other than ethanol, such as isobutanol. This transferability establishes the eSSF process as a platform for the sustainable production of biofuels and chemicals as a whole.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cellulosic biofuel production using emulsified simultaneous saccharification and fermentation (eSSF) with conventional and thermotolerant yeasts

Hoffman

Álvarez

Alfassi

et al. 2021

Biotechnol Biofuels

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“…In industrial-scale fermentations, the utilization of starter cultures is preferred over spontaneous inoculations to avoid technical hitches related to slow fermentation rates, end product variability, and yeast contaminants that can spoil the final product (Eliodório et al, 2019;Parapouli et al, 2020). Commercial yeast strains are isolates from fermentation-related environments or are derived from breeding programs, in which they were selected for certain phenotypic traits, such as efficient nitrogen consumption (García-Ríos et al, 2014;Tesnière et al, 2015), fast fermentation rates (Preiss et al, 2018), and pleasant aroma profiles (Eder et al, 2018;Schwarz et al, 2020).…”

Section: All That Glitters Is Not Gold: Advantages and Disadvantages mentioning

confidence: 99%

Wild Yeast for the Future: Exploring the Use of Wild Strains for Wine and Beer Fermentation

Molinet

Cubillos

2020

Front. Genet.

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The continuous usage of single Saccharomyces cerevisiae strains as starter cultures in fermentation led to the domestication and propagation of highly specialized strains in fermentation, resulting in the standardization of wines and beers. In this way, hundreds of commercial strains have been developed to satisfy producers' and consumers' demands, including beverages with high/low ethanol content, nutrient deprivation tolerance, diverse aromatic profiles, and fast fermentations. However, studies in the last 20 years have demonstrated that the genetic and phenotypic diversity in commercial S. cerevisiae strains is low. This lack of diversity limits alternative wines and beers, stressing the need to explore new genetic resources to differentiate each fermentation product. In this sense, wild strains harbor a higher than thought genetic and phenotypic diversity, representing a feasible option to generate new fermentative beverages. Numerous recent studies have identified alleles in wild strains that could favor phenotypes of interest, such as nitrogen consumption, tolerance to cold or high temperatures, and the production of metabolites, such as glycerol and aroma compounds. Here, we review the recent literature on the use of commercial and wild S. cerevisiae strains in wine and beer fermentation, providing molecular evidence of the advantages of using wild strains for the generation of improved genetic stocks for the industry according to the product style.

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“…World bioethanol production is ca. 100 billion litres from corn, sugarcane, or wheat, using the industrial workhorse Saccharomyces cerevisiae (1, 2). The fermentation yield defined as grams of ethanol that can be obtained per gram of sugar is the most important parameter in this industrial process (3).…”

Section: Introductionmentioning

confidence: 99%

Blocking mitophagy does not improve fuel ethanol production in Saccharomyces cerevisiae

Cunha

et al. 2021

Preprint

Self Cite

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Ethanol fermentation is frequently performed under conditions of low nitrogen. In Saccharomyces cerevisiae, nitrogen limitation induces macroautophagy, including the selective removal of mitochondria, also called mitophagy. Shiroma and co-workers (2014) showed that blocking mitophagy by deletion of the mitophagy specific gene ATG32 increased the fermentation performance during the brewing of Ginjo sake. In this study, we tested if a similar strategy could enhance alcoholic fermentation in the context of fuel ethanol production from sugarcane in Brazilian biorefineries. Conditions that mimic the industrial fermentation process indeed induce Atg32-dependent mitophagy in cells of S. cerevisiae PE-2, a strain frequently used in the industry. However, after blocking mitophagy, no differences in CO2production, final ethanol titres or cell viability were observed after five rounds of ethanol fermentation, cell recycling and acid treatment, as commonly performed in sugarcane biorefineries. To test if S. cerevisiae's strain background influences this outcome, cultivations were carried out in a synthetic medium with strains PE-2, Ethanol Red (industrial) and BY (laboratory), with and without a functional ATG32 gene, under oxic and oxygen restricted conditions. Despite the clear differences in sugar consumption, cell viability and ethanol titres, among the three strains, we could not observe any improvement in fermentation performance related to the blocking of mitophagy. We conclude with caution that results obtained with Ginjo sake yeast is an exception and cannot be extrapolated to other yeast strains and that more research is needed to ascertain the role of autophagic processes during fermentation.

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Advances in yeast alcoholic fermentations for the production of bioethanol, beer and wine

Cited by 42 publications

References 167 publications

Cellulosic biofuel production using emulsified simultaneous saccharification and fermentation (eSSF) with conventional and thermotolerant yeasts

Cellulosic biofuel production using emulsified simultaneous saccharification and fermentation (eSSF) with conventional and thermotolerant yeasts

Wild Yeast for the Future: Exploring the Use of Wild Strains for Wine and Beer Fermentation

Blocking mitophagy does not improve fuel ethanol production in Saccharomyces cerevisiae

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