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Microbial cellulases have been receiving worldwide attention, as they have enormous potential to process the most abundant cellulosic biomass on this planet and transform it into sustainable biofuels and other value added products. The synergistic action of endoglucanases, exoglucanases, and β-glucosidases is required for the depolymerization of cellulose to fermentable sugars for transformation in to useful products using suitable microorganisms. The lack of a better understanding of the mechanisms of individual cellulases and their synergistic actions is the major hurdles yet to be overcome for large-scale commercial applications of cellulases. We have reviewed various microbial cellulases with a focus on their classification with mechanistic aspects of cellulase hydrolytic action, insights into novel approaches for determining cellulase activity, and potential industrial applications of cellulases.

Biologically synthesized nanoparticles are gaining importance as they offer several advantages, such as the ease with which they can be scaled up, the cost-effectiveness of the process and the green route of production. In this study, silver (Ag) nanoparticles were biosynthesized using the cellular extract of Penicillium oxalicum GRS-1 and then characterized by ultraviolet visible spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy. The biosynthesis of nanoparticles was optimized by following the one factor at a time approach, wherein the temperature of 60°C, pH 7.0 and 1.5 mm silver nitrate (AgNO3) concentration were found to be most favorable factors for the production of Ag nanoparticles. Upon statistical optimization, the maximum production of Ag nanoparticles with a concentration of 136 ppm was achieved at pH 7.2, AgNO3 concentration 1.975 mm and 86 h using the crude cellular extract of P. oxalicum GRS-1 having nitrate reductase activity. TEM analysis showed that the Ag nanoparticles were spherical in shape with sizes ranging from 10 to 40 nm. The biosynthesized nanoparticles showed strong antimicrobial activity against the common food-borne, pathogens including Staphylococcus aureus, Escherichia coli and Salmonella typhimurium with respective minimum bactericidal concentrations of 32, 16 and 32 μg/ml.

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This is an attempt to lower the cost of starch hydrolysis by the discovery of new generation a-amylase. A natural isolate of Bacillus subtilis subsp. spizizenii was capable of producing appreciable amounts of raw potato starch digesting a-amylase in solid state fermentation of wheat bran. The enzyme productivity has been substantially enhanced by supplementing various nutrients and statistically studying their interactions by response surface methodology. A central composite design for amylase production system elucidated a wheat branbased medium supplemented with soybean meal, threonine, and B-complex vitamins predicting a yield of 521 391 U/g dry solids. The enzyme preparation could effectively digest 5-15% suspension of insoluble potato starch in 6 h revealing the dextrose equivalent of 32-44. The supplementation of a glucoamylase preparation, thereafter, brought about complete saccharification. The yield achieved in the statistically optimized amylase system may be one of the best to date and its capability in directly liquefying raw potato starch granules makes this study novel.