Microwave-assisted pretreatment of maize distillery stillage with the use of dilute sulfuric acid in the production of cellulosic ethanol

This study aimed to evaluate the effectiveness of microwave-assisted pretreatment in production of cellulosic bioethanol from maize distillery stillage. High glucose concentration (104.4 +/- 0.4 mg/g dry weight) and the highest yield of enzymatic cellulose hydrolysis (75.8 +/- 0.9%) were obtained for microwave pretreatment characterized by the following parameters: 300 W, 54 PSI, 15 min. Such pre-treatment parameters allowed the obtaining of not only a high concentration of glucose, but also a low concentration of fermentation inhibitors, i.e. 5-hydroxymethylfurfural (6.8 +/- 0.4 mg/g of DW) and furfural (6.0 +/- 1.2 mg/g dry weight). Optimal dose of yeast, Saccharomyces cerevisiae strain Ethanol Red which gave a high attenuation was 2 g/L of cellulose fermentation medium. Detoxification of cellulose hydrolysates with activated carbon enabled achieving high fermentation yield (approximately 77% of the theoretical yield). Microwave processing can be an effective pretreatment method in production of cellulosic ethanol from maize distillery stillage, but this process requires careful selection of parameters.