An extracellular β-glucosidase was isolated from Proteus mirabilis VIT117 found to be growing on prawn shells. The enzyme production was found to be enhanced (14.58 U/ml) when the culture was maintained at pH 9 and provided with sorbitol as carbon source, yeast extract as nitrogen source and incubated at 37 °C for approximately 72 h. Statistical methods like Plackett–Burman and RSM were also applied here to study the effects of different combinations of growth parameters for the bacteria, where the most significant parameters were found to be inoculum size, pH, yeast extract, incubation time and sorbitol. The optimum concentrations of inoculum size, pH and yeast extract determined by RSM were 2 %, 9 and 2 %, respectively. Partial purification of the protein was done by ammonium sulfate precipitation, followed by dialysis, gel filtration chromatography and SDS-PAGE. The enzyme was found to have a molecular weight of approximately 50 kDa and was observed to be most active at 37 °C in pH 9, with a sharp decline in the enzyme activity when temperature or the pH was increased. Enzyme kinetics study was performed to understand the catalytic behavior of the enzyme and it was found that our β-glucosidase had 5.613 U/ml and 0.082 mM as V max and K m values, respectively.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-016-0530-7) contains supplementary material, which is available to authorized users.

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Ethanol is the most commonly used biofuel in the world, its demand increasing with time. Due to the steady rate of depletion of fossil fuels, bioethanol is emerging as an alternative fuel source. Unlike fossil fuels, bioethanol is a clean fuel that is environment friendly and causes little pollution. It is an alcohol, resulting from the fermentation of sugars, starches or cellulose, derived from crops such as wheat, corn, sugar beets, sugarcane, agricultural residues or any other lignocellulosic biomass. The production is a multi-step process that includes a range of pre-treatments, enzymatic hydrolysis and fermentation. The final product, ethanol, is obtained from the final step of fermentation that is carried out with the help of microorganisms like yeast or bacteria, or even a combination of microorganisms. Researches are being carried out to genetically engineer or find natural indigenous microorganisms that are capable of producing specific enzymes required for the production of bioethanol in large amounts that is suitable for industrial scale. Bioethanol is currently being blended with gasoline and used as automobile fuel for vehicles with gasoline engines. In this article, the various sources of raw materials that can be used for bioethanol production have been discussed, along with descriptions of the different production steps involved in the generation of bioethanol on an industrial scale.