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Plant biomass possesses a huge potential as a source for biofuel production. The main components of biomass are glucose and five-carbon sugar xylose. The yeast Saccharomyces cerevisiae that is used for industrial ethanol production from glucose is unable to xylose fermentation. Therefore a microorganism capable for efficient fermentation of both glucose and xylose has to be found in nature or constructed for economically feasible biomass conversion to ethanol. The active xylose fermentation could be performed by increasing the efficiency of initial stages of xylose metabolism. In this review the enzymes of initial stages of xylose metabolism in yeasts (xylose reductase, xylitol dehydrogenase, xylulokinase) and bacteria (xylose isomerase and xylulokinase) are characterized. The ways for construction of yeast strains capable of efficient alcoholic xylose fermentation are discussed.

The influence of aromatic compounds and Mn ions on activities of ligninolityc enzymes from white-rot fungus Pleurotus floridae has been studied. The specific inducers: vanillic acid and vanillyl alcohol--for activity of manganese-dependent peroxidase; vanillyl alcohol--for activity of cellobiose: quinone oxidoreductase during submerged, fermentation of Pleurotus floridae in Kirk's medium have been revealed. The inducers of laccase activity among studied aromatic compounds have not been revealed. The influence of Mn2+ in concentration range 0.4-68.4 mM on activities of ligninolytic enzymes of submerged culture of fungus P. floridae has been studied. Concentration of Mn ions 32.4 mM was optimal for manganese-dependent peroxidase activity.