The present study deals with the enhanced production of polyhydroxybutyrate (PHB) using a novel potent strain. On the basis of morphological, biochemical, and 16S rRNA analysis, the strain was identified as Bacillus safensis EBT1. The presence of PHB in the cells was identified and affirmed using fluorescent microscopy and Fourier transform infrared spectroscopy. The molecular weight of PHB was ascertained by gel permeation chromatography. Under optimized conditions, B. safensis EBT1 showed maximum PHB production and growth with glucose as the carbon source, yeast extract as the nitrogen source, and sugarcane bagasse as the substrate. The process parameters were optimized using central composite design: pH 7, 45°C and 48 h incubation time. At these conditions, highest biomass concentration of 7.54 g/L and PHB production of 6.41 g/L were observed.
The kinetic model of cell growth is substantially capable to predict product formation. Mathematical models provide a strategy for solving problems encountered in fermentation process. A biochemical engineering approach to address this problem could be to develop a mathematical model which not only helps in the understanding of the system but also predicts various cultivation strategies to facilitate the optimization of a fermentation process, saving much of the time and cost for performing experiments. The presented overview indicates that many of the environmentally relevant aspects in growth kinetics are still waiting to be discovered, established, and exploited. A kinetic model that describes microbial growth, product formation and substrate consumption and the experimental data were fitted with modified logistic equation.
a b s t r a c tOver the past few years, there is an increasing demand for bio-butanol production using renewable resources through microbial fermentation. In our study, we isolated a high yielding butanol producing fungal strain Trichoderma atroviridae SS2 from soil. First half of the paper mainly deals with the xylanase production using newly isolated fungal strain Hypocrea lixii SS1 around an oil refinery plant. Media optimization for xylanase production was carried out using Plackett Burman design (PB) and Response Surface Methodology (RSM) methods by changing the concentrations of carbonaceous, nitrogen and surfactant sources. Maximum yield of xylanases obtained were 34.67 U/ml, 38.36 U/ml, 37.18 U/ml using sunflower oil sludge (carbon source), peptone (nitrogen source), and Tween 80 (surfactant), respectively. The second half of the paper mainly deals with the butanol production using T. atroviridae SS2 along with the xylanase produced by H. lixii SS1. Influence of incubation time, microbial volume xylanase volume, pH and temperature were investigated on butanol production. A maximum butanol yield of 18.94 g/L was achieved using 80 g/L microbial culture, 4 ml xylanase and a 7 days incubation period respectively. A narrow peak obtained at 285 nm with a retention time of 28.38 min using High Performance Liquid Chromatography (HPLC) confirms the presence of butanol.
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