To develop a suitable Saccharomyces cerevisiae industrial strain as a chassis cell for ethanol production using lignocellulosic materials, 32 wild-type strains were evaluated for their glucose fermenting ability, their tolerance to the stresses they might encounter in lignocellulosic hydrolysate fermentation and their genetic background for pentose metabolism. The strain BSIF, isolated from tropical fruit in Thailand, was selected out of the distinctly different strains studied for its promising characteristics. The maximal specific growth rate of BSIF was as high as 0.65 h−1 in yeast extract peptone dextrose medium, and the ethanol yield was 0.45 g g−1 consumed glucose. Furthermore, compared with other strains, this strain exhibited superior tolerance to high temperature, hyperosmotic stress and oxidative stress; better growth performance in lignocellulosic hydrolysate; and better xylose utilization capacity when an initial xylose metabolic pathway was introduced. All of these results indicate that this strain is an excellent chassis strain for lignocellulosic ethanol production.

Bioethanol production from lignocellulose is considered as a sustainable biofuel supply. However, the low cellulose hydrolysis efficiency limits the cellulosic ethanol production. The cellulase is strongly inhibited by the major end product cellobiose, which can be relieved by the addition of β-glucosidase. In this study, three β-glucosidases from different organisms were respectively expressed in Saccharomyces cerevisiae and the β-glucosidase from Saccharomycopsis fibuligera showed the best activity (5.2 U/ml). The recombinant strain with S. fibuligera β-glucosidase could metabolize cellobiose with a specific growth rate similar to the control strain in glucose. This recombinant strain showed higher hydrolysis efficiency in the cellulose simultaneous saccharification and fermentation, when using the Trichoderma reesei cellulase, which is short of the β-glucosidase activity. The final ethanol concentration was 110% (using Avicel) and 89% (using acid-pretreated corncob) higher than the control strain. These results demonstrated the effect of β-glucosidase secretion in the recombinant S. cerevisiae for enhancing cellulosic ethanol conversion.

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Supercritical fluid extraction (SFE) is one of the most commonly used extraction techniques in the course of analysis or preparation. It is environmentally friendly and has some advantages over other conventional extraction methods. This review covers the recent developments of SFE in the extraction of essential oils from the plant materials during the period 2005 to 2011, in particular some factors influencing SFE extraction yield, its characteristics and applications.