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The European Union has recommended that about 10–50% of the global energy requirement should be supplemented by waste biomass resources by 2050 in order to achieve the objective of having net-zero-emission economies. This has led to intensive research being conducted on developing appropriate biofuel production technologies using advanced or integrated systems to tackle local, national, and global energy challenges using waste feedstock. Researchers have realized the potential of microbes (e.g., yeast strains) for bioenergy production. For this paper, both non-oleaginous and oleaginous yeasts were reviewed, with a specific focus being placed on their diversity in metabolism and tolerance to the various challenges that arise from the use of waste feedstock and influence bioprocessing. Gathering in-depth knowledge and information on yeast metabolism has paved the way for newer and better technologies to employ them for consolidated biorefineries to not only produce biofuels but also to cut down process expenses and decrease the risks of net carbon emissions. The rationale for using yeast strains improved by metabolic engineering and genetic manipulation that can substantially meet the challenges of alternate fuel resources is also described in this paper. This literature review presents the advantages and disadvantages of yeast-based biofuel production and highlights the advancements in technologies and how they contrast to conventional methods. Over the last decade, scientific publications have endorsed the idea of biorefineries for environmentally friendly, cost-effective, and sustainable biofuel production. [ABSTRACT FROM AUTHOR]

Carotenoid production from oleaginous red yeast has been considered as a safe alternative to chemically synthesized carotenoids commonly used in the food industry, since plant-based carotenoids are expensive and an irregular source for obtaining pigments. This is a summative review on the factors affecting carotenoid production, cost-effective production strategies using various inexpensive feedstock, metabolic engineering, and strain improvisation. The review specially highlights the various potential applications of carotenoids as anti-microbial, anti-viral, antioxidant, anti-cancerous, anti-malarial agents, etc. The importance of such natural and easily available resources for prevention, evasion, or cure of emerging diseases and their plausible nutraceutical effect demands exhaustive research in this area. [ABSTRACT FROM AUTHOR]

As a replacement to existing fossil fuels, biofuels, have proven their worth; however, their widespread use is limited due to inconsistent yields, higher costs and poor productivity. An oleaginous yeast, Rhodosporidium toruloides has been reported to accumulate substantial amounts of lipids (that can be converted to biofuels) and therefore, it was selected for study and optimization. Apart from lipids, R. toruloides is also reported to produce carotene that can be used as a therapeutic agent. In this study, the culture medium was statistically modeled and optimized for concomitant production of lipids and carotenoids and for improving and maximizing the productivity of lipids as well as carotenes. The two metabolites were expressed differentially in the growth cycle of the organism. Culture medium components were simultaneously varied at five different levels using statistical modeling employing response surface methodology (RSM). Osmotic stress was introduced in order to simulate saline conditions and optimize the carotenoid as well as lipid production process, to be used in conditions with high salt contents. We observed a 10% (w/v) increase in carotenoid production in initial experiments under osmotic stress due to high salt concentration, while the increase in lipid synthesis was not pronounced. In this study, we demonstrate 36.2% (w/v) lipid production and 27.2% (w/v) carotenoid production, under osmotic stress with high salt concentrations, for the first time. [ABSTRACT FROM AUTHOR]

Upon publication of this article [1], the authors realized that one of the coauthor name was accedentally deleted during the review process and not presented in the original version of the article. The coauthor Dr. Ram Prasad should be listed as fifth author. The corrected author group is published with this erratum. [ABSTRACT FROM AUTHOR]

Background: Bioethanol obtained by fermenting cellulosic fraction of biomass holds promise for blending in petroleum. Cellulose hydrolysis yields glucose while hemicellulose hydrolysis predominantly yields xylose. Economic feasibility of bioethanol depends on complete utilization of biomass carbohydrates and an efficient co-fermenting organism is a prerequisite. While hexose fermentation capability of Saccharomyces cerevisiae is a boon, however, its inability to ferment pentose is a setback.Results: Two xylose fermenting Kodamaea ohmeri strains were isolated from Lagenaria siceraria flowers through enrichment on xylose. They showed 61% glucose fermentation efficiency in fortified medium. Medium engineering with 0.1% yeast extract and peptone, stimulated co-fermentation potential of both strains yielding maximum ethanol 0.25 g g−1 on mixed sugars with ~ 50% fermentation efficiency. Strains were tolerant to inhibitors like 5-hydroxymethyl furfural, furfural and acetic acid. Both K. ohmeri strains grew well on biologically pretreated rice straw hydrolysates and produced ethanol.Conclusions: This is the first report of native Kodamaea sp. exhibiting notable mixed substrate utilization and ethanol fermentation. K. ohmeri strains showed relevant traits like utilizing and co-fermenting mixed sugars, exhibiting excellent growth, inhibitor tolerance, and ethanol production on rice straw hydrolysates. [ABSTRACT FROM AUTHOR]