Analysis of metabolite profiles of Saccharomyces cerevisiae strains suitable for butanol production.

Butanol has advantages over ethanol as a biofuel. Although butanol is naturally produced by some Clostridium species, clostridial fermentation has inherent characteristics that prevent its industrial application. Butanol-producing Saccharomyces cerevisiae strains may be a solution to this problem. The aim of this study was to evaluate the ability of wild-type and industrial Brazilian strains of S. cerevisiae to produce n-butanol using glycine as co-substrate and evaluate the relationship between the production of this alcohol and other metabolites in fermented broth. Of the 48 strains analyzed, 25 were able to produce n-butanol in a glycine-containing medium. Strains exhibited different profiles of n-butanol, isobutanol, ethanol, glycerol and acetic acid production. Some wild-type strains showed substantial n-butanol production capability, for instance UFMG-CM-Y267, which produced about 12.7 mg/L of butanol. Although this concentration is low, it demonstrates that wild-type S. cerevisiae can synthesize butanol, suggesting that selection and genetic modification of this microorganism could yield promising results. The findings presented here may prove useful for future studies aimed at optimizing S. cerevisiae strains for butanol production.

A review of research trends in the enhancement of biomass-to-hydrogen conversion.

Different types of biomass are being examined for their optimum hydrogen production potentials and actual hydrogen yields in different experimental set-ups and through different chemical synthetic routes. In this review, the observations emanating from research findings on the assessment of hydrogen synthesis kinetics during fermentation and gasification of different types of biomass substrates have been concisely surveyed from selected publications. This review revisits the recent progress reported in biomass-based hydrogen synthesis in the associated disciplines of microbial cell immobilization, bioreactor design and analysis, ultrasound-assisted, microwave-assisted and ionic liquid-assisted biomass pretreatments, development of new microbial strains, integrated production schemes, applications of nanocatalysis, subcritical and supercritical water processing, use of algae-based substrates and lastly inhibitor detoxification. The main observations from this review are that cell immobilization assists in optimizing the biomass fermentation performance by enhancing bead size, providing for adequate cell loading and improving mass transfer; there are novel and more potent bacterial and fungal strains which improve the fermentation process and impact on hydrogen yields positively; application of microwave irradiation and sonication and the use of ionic liquids in biomass pretreatment bring about enhanced delignification, and that supercritical water biomass processing and dosing with metal-based nanoparticles also assist in enhancing the kinetics of hydrogen synthesis. The research areas discussed in this work and their respective impacts on hydrogen synthesis from biomass are arguably standalone. Thence, further work is still required to explore the possibilities and techno-economic implications of combining these areas for developing robust and integrated biomass-to-hydrogen synthetic schemes.