Search

Abstract: (1R,4R)-dihydrocarvone (2), an important renewable building block, was prepared with good conversions and excellent diastereoisomeric excess through the reduction of the α,β-unsatured carbon–carbon double bond of (4R)-(−)-carvone (1) mediated by Baker''s yeast (BY) in aqueous mono- and biphasic systems. Some parameters that may alter this bioreduction reaction, such as the concentrations of yeast and substrate, temperature, and pH, were evaluated. The effect of the addition of different additives on the course of 1 biotransformation was also investigated. The results showed that the conversion and diastereoisomeric excesses were strongly dependent on these variables. The optimum reaction conditions were 100gL−1 of BY, 16.6mM of substrate, and pH 7.5 at 26°C in the presence of DMSO, trehalose, or sucrose as additives. Under the optimum conditions, the (1R,4R)-dihydrocarvone was recovered with diastereoisomeric excesses of 92–99% and with conversions of 70–74%. [Copyright &y& Elsevier]

Abstract: A series of chalcones (1–9) was synthesized by base catalyzed aldol condensation with 50–94% yields. These α,β-unsaturated carbonyl compounds were used as substrates in biotransformation reactions mediated by three industrial Saccharomyces cerevisiae strains in biphasic systems. Several reaction parameters were evaluated, such as yeast concentration, temperature, pH, substrate concentration, organic solvent, volume of aqueous and organic phases and the influence of substituent groups on chalcones 1–9. The biotransformation was chemoselective and formed only the corresponding saturated ketones. The highest conversion (>99%) to the dihydrochalcone was obtained at 30–45°C and pH above 5.5, while the cellular and substrate concentrations also showed a strong influence on the biohydrogenation reaction. Organic solvents with log P >3.2 (hexane or heptane) were the most appropriate, and 40–80% of aqueous phase allowed the highest conversions probably by maintaining the yeast enzymes catalytically active. The influence of substituents on rings A and B of chalcones 1–9 was low and no correlation between the donor or withdrawing electron groups was observed. [Copyright &y& Elsevier]

Sucrose is an abundant, readily available and inexpensive substrate for industrial biotechnology processes and its use is demonstrated with much success in the production of fuel ethanol in Brazil. Saccharomyces cerevisiae, which naturally evolved to efficiently consume sugars such as sucrose, is one of the most important cell factories due to its robustness, stress tolerance, genetic accessibility, simple nutrient requirements and long history as an industrial workhorse. This minireview is focused on sucrose metabolism in S. cerevisiae, a rather unexplored subject in the scientific literature. An analysis of sucrose availability in nature and yeast sugar metabolism was performed, in order to understand the molecular background that makes S. cerevisiae consume this sugar efficiently. A historical overview on the use of sucrose and S. cerevisiae by humans is also presented considering sugarcane and sugarbeet as the main sources of this carbohydrate. Physiological aspects of sucrose consumption are compared with those concerning other economically relevant sugars. Also, metabolic engineering efforts to alter sucrose catabolism are presented in a chronological manner. In spite of its extensive use in yeast-based industries, a lot of basic and applied research on sucrose metabolism is imperative, mainly in fields such as genetics, physiology and metabolic engineering. [ABSTRACT FROM AUTHOR]

This study aimed to isolate a yeast strain and evaluate its potential to be inoculated in the biofloc technology culture of Pacific white shrimp employing in vitro and in vivo assays. A yeast strain identified as Meyerozyma guilliermondii (CPQBA 1459/17 DRM‐01) was isolated from the soil of an estuary. Its growth kinetics under different salinities (0%, 1.0%, 2.0%, 3.0% NaCl) and Vibrio alginolyticus inhibition were evaluated in vitro. For the in vivo assay, a factorial design was employed to evaluate the effects of yeast addition and biofloc management strategy in the nursery culture of Litopenaeus vannamei as regards shrimp growth performance, water quality and water microbiology. The two factors evaluated were biofloc (mature and heterotrophic) and yeast (addition or no addition), totaling four treatments. In the in vitro trials, the yeast strain was capable of growing under all salinities evaluated, but no pathogen inhibition was observed. In the in vivo experiment, the addition of yeast significantly reduced the concentration of total suspended solids (p < 0.05), in addition to promoting a higher post‐larvae survival when considering only the two mature biofloc treatments (p < 0.05). No significant effects on water Vibrio spp. and total heterotrophic bacteria counts were found (p ≥ 0.05). In conclusion, the inoculation of yeast in the biofloc culture of L. vannamei exhibited bioremediation potential and improvement in shrimp survival, the latter being modulated by the biofloc management strategy. [ABSTRACT FROM AUTHOR]

Abstract: Haploid Saccharomyces cerevisiae W303-1A cells grown on different carbon sources were employed as the biocatalyst for ethyl acetoacetate reduction in n-hexane. The effects of cell immobilization on montmorillonite, as well as the addition of trehalose or sucrose solutions, were also tested. Best conversions (∼50%) to the chiral alcohol ethyl (S)-(+)-3-hydroxybutanoate (ee>99%) were obtained with cells grown under respiratory metabolism with glycerol–ethanol, and higher yields were observed when trehalose was added to the reaction media. Although cells with fermentative metabolism grown on glucose were able to reduce the substrate when sucrose was added, the disaccharide was consumed by the cells during the course of the reaction, and no enantioselective product was obtained. Immobilized cells also required the addition of trehalose in order to reduce the substrate with high yield. Thus, our results indicate that trehalose may be an efficient protector of immobilized or free yeast cells during enantioselective reductions in organic solvent. [Copyright &y& Elsevier]

Highlights: [•] A green method hollow-fiber liquid–liquid–liquid microextraction (HF-LLLME) is reported. [•] Bioreduction of (4S)-carvone was mediated by yeasts in aqueous mono or biphasic systems. [•] The RSM was used for evaluated the experimental parameters in the bioreduction of 1. [•] (1R,2R,4S)-dihydrocarveol was obtained with conversion of 52.7% and d.e.>99%. [Copyright &y& Elsevier]

In this study, we evaluated the potential of yeasts isolated from Amazon to produce second-generation ethanol from sugarcane bagasse delignified with alkaline hydrogen peroxide and hydrolysed with commercial enzyme preparation. The best efficiency savings in glucose and release of xylose were determined by considering the solids and enzyme loads. Furthermore, we selected Spathaspora passalidarum UFMG-CM-Y473 strain with the best fermentative parameters. Fermentations used bagasse hydrolysate without any nutritional supplementation, a significant difference from previous studies, which is closer to industrial conditions. Ethanol yield of 0.32 g/g and ethanol productivity of 0.34 g/L h were achieved after the consumption of 78% of the sugar. This hydrolysis/fermentation technology package could represent the input of an additional 3180 L of ethanol per hectare in areas of average sugarcane productivity such as 60 ton/ha. Thus, we concluded that Sp. passalidarum UFMG-CM-Y473 has a clear potential for the production of second-generation ethanol from delignified and enzyme-hydrolysed bagasse. [ABSTRACT FROM AUTHOR]