Enhanced biobutanol production by optimization of the medium from Clostridium acetobutylicum MTCC 11274 using macroalgae Gracilaria edulis

Abstract

Clostridial strain Clostridium acetobutylicum MTCC 11274 was employed for producing biobutanol in batch culture fermentation. The effects of various carbon sources, i.e., xylose, starch, dextrin, glucose, and mannose as well as nitrogen sources, i.e., yeast extract, peptone, beef extract, and soya protein were studied conventionally (one-factor-at-a-time). It was found that the maximum amount of biobutanol, i.e., 6.27 and 7.40 g/l was obtained from 60 g/l glucose and 5 g/l yeast extract, respectively. In addition to this, the interactions between pH, temperature, and glucose concentration were also taken into consideration for the optimization of biobutanol production with the help of Central Composite Design (CCD) of Response Surface Methodology. CCD design was used for the optimization of the above-mentioned parameters and low and high values of variables were chosen by performing the steepest ascent experiment. The analysis of variance (ANOVA) model was used for estimating the significance of the model coefficients. ANOVA revealed that the model was significant (p < 0.05) and the effects of the glucose concentration, pH, and temperature on biobutanol production were significant. It was found that 8.56 g/l biobutanol was produced under optimum fermentation conditions with 40 g/l Gracilaria edulis supplemented with 20 g/l glucose as a carbon source.