Evaluation of stress tolerance and fermentative behavior of indigenous Saccharomyces cerevisiae

Abstract

Sixty six indigenous Saccharomyces cerevisiae strains were evaluated in stressful conditions (temperature, osmolarity, sulphite and ethanol tolerance) and also ability to flocculate. Eighteen strains showed tolerant characteristics to these stressful conditions, growing at 42 °C, in 0.04% sulphite, 1 mol L−1 NaCl and 12% ethanol. No flocculent characteristics were observed. These strains were evaluated according to their fermentative performance in sugar cane juice. The conversion factors of substrates into ethanol (Yp/s), glycerol (Yg/s) and acetic acid (Yac/s), were calculated. The highest values of Yp/s in sugar cane juice fermentation were obtained by four strains, one isolated from fruit (0.46) and the others from sugar cane (0.45, 0.44 and 0.43). These values were higher than the value obtained using traditional yeast (0.38) currently employed in the Brazilian bioethanol industry. The parameters Yg/s and Yac/s were low for all strains. The UFLA FW221 presented the higher values for parameter related to bioethanol production. Thus, it was tested in co-culture with Lactobacillus fermentum. Besides this, a 20-L vessel for five consecutive batches of fermentation was performed. This strain was genetically stable and remained viable during all batches, producing high amounts of ethanol. The UFLA FW221 isolated from fruit was suitable to produce bioethanol in sugar cane juice. Therefore, the study of the biodiversity of yeasts from different environmental can reveal strains with desired characteristics to industrial applications.

Heterologous expression of cellulase genes in natural Saccharomyces cerevisiae strains

“…Unlike the domesticated S. cerevisiae strains, environmental isolates are Some of these phenotypic differences observed in this study have been previously reported in the context of other studies (13,19,95,(97)(98)(99) Table 4A). …”

“…The supplementation with BGLs during hydrolysis, and removal of sugars during hydrolysis by ultra-filtration or SSF are some of the methods that have been developed to reduce inhibition of hydrolysis (94). Consolidated bio-processing (CBP) is one of the strategies that have been proposed as a solution to reduce enzyme cost contribution, whereby a single microorganism capable of both producing biomass hydrolysing enzymes and fermenting the released sugars to ethanol e.g., a fermentative microbe is engineered with a cellulolytic system (95). Previous studies have used a variety of strains and conditions to express recombinant cellulolytic enzymes, which is problematic since the impact of the secretion of recombinant proteins on gene expression is influenced by the genetic background of the host strains (79,96,97).…”

Enological Qualities and Interactions Between Native Yeast and Lactic Acid Bacteria from Queretaro, Mexico

“…Flocculation was estimated by suspending a 5‐mL pellet of yeast culture in Helm reagent. Then, OD was immediately measured (OD initial ) with a spectrophotometer and 1 hr after suspension (OD final ) to calculate the following: (Ramos et al., ). The killer phenotype was observed by the inhibition halos produced on plates of the sensitive Saccharomyces ATCC 38,626 strain (Lopes & Sangorrín, ).…”

Kinetics of Bioethanol Production from Waste Sorghum Leaves Using Saccharomyces cerevisiae BY4743

“…A productivity of 0.345 g/L/h was observed in this study. Ethanol productivities on other lignocellulosic substrates in the range of 0.25 to 1.01 g/L/h have been reported [35][36][37][38], further pointing to the relative higher potential of waste sorghum leaves for bioethanol production.…”

“…A productivity of 0.345 g/L/h was observed in this study. Ethanol productivities on other lignocellulosic substrates in the range of 0.25 to 1.01 g/L/h have been reported [35][36][37][38], further pointing to the relative higher potential of waste sorghum leaves for bioethanol production. The fitted regression curve exhibited an R 2 value of 0.98 and a correlation coefficient (r) of 0.99, suggesting that this model is able to efficiently describe bioethanol production during the fermentation of sorghum leaf wastes.…”