Evaluation of the possibility of using brewer’s spent grain for the fermentation of lignocellulosic hydrolysates to biobutanol

The paper deals with the investigation of the possible using of brewer’s grain as a source of growth substabces in acetone-butanol fermentation of lignocellulosic hydrolysates in order to reduce the cost of biobutanol production and to utilize the brewery waste. The fermentation of glucose was carried out at different concentrations of the brewer’s grain by Clostridium acetobutylicum ATCC 824. In the experiments on fermentation of the lignocellulosic hydrolysates an enzymatic hydrolysate of miscanthus cellulose containing 34.8 g/l glucose and 15.6 g/l xylose was used as a source of reducing substances. The sterilization of the medium was carried out at 0.5 KPa for 20 minutes. The sterilization of the growth and reducing substances sources was conducted separately to prevent caramelization of products and melanoidins. For inoculation the spores of 3% (vol/vol) C. acetobutylicum ATCC 824 were transferred to a fresh medium. The strain was grown at 37 °С under anaerobic conditions. In a series of experiments on the evaluation of the influence of the brewer’s grain on the fermentability of carbohydrates by the strain of C. acetobutylicum АТСС 824, limiting and inhibitive concentrations of brewer’s grain were determined in the medium, which were 2 and 20 % vol., respectively. The optimal amount of the brewer’s grain was about 6 % vol. At the optimal concentration of the brewer’s grain the fermentation of lignocellulosic hydrolysates occured in all replicates. It was characterized by intensive gas and foam formation that corresponds to the data in literature. After 79-88 h of fermentation of miscanthus cellulose hydrolysate the product yield amounted 10.14±0.87 g/L butanol, 02.48±0.53 acetone, 01.02±0.42 g/L ethanol. It was found that at an optimum concentration both the fresh and sour brewer’s grain can be used in the fermentation. After the acetone-butanol fermentation the brewer’s grain can be used as a food for farm animals. The obtained results indicate the possibility of using the brewer’s grain as a source of growth substances for the fermentation of lignocellulosic hydrolysates. The proposed method of using the brewer’s grains in acetone-butanol fermentation may reduce the cost of biobutanol and also solve the problem of disposing some waste from the brewing industry.