Utilization of different agro-industrial wastes for bioethanol production using an amylolytic potential from the Paenibacillus chitinolyticus CKS1

Abstract

Agro-industrial waste worldwide represents renewable resources (raw materials) that accumulate throughout the year. To awoid excessive accumulation of wastemore attention has been paid to the bioconversion of waste raw materials by microorganisms for obtainingthe biotechnologically valuable products. During the last few decades, enzymes mainly produced by microorganisms used in a hydrolysis process of agroindustrial waste substrates for obtaining liquid fuels are specifically requested.Bioethanol, as an alternative to petroleum based fuel, is one of the dominating renewable liquid fuels on the market. Released simple sugars by enzymatic hydrolysis of waste materials are fermented by yeast Saccharomyces cerevisiae into ethanol. In this study, four different agroindustrial wastes: damaged rice grains, barley bran, corn meal and wastewater from transport packaging that contains starch glue were used as substrates for enzymeamylase production by P. chitinolyticus CKS1. Among them barley bran (4% barley bran, yeast extract 3g/l and casein hydrolysate 5g/l; 30 °C, 120 rpm, 48 h) showed maximum amylase production 1.65 U/ml. Enzymatic hydrolysis of different strach waste materials: damaged rice grains, barley bran, corn meal and wastewater from transport packaging using crude amylases showed that maximu reducing sugars 21.11 mg/ml were obtained using damaged rice grains. Optimal concentration of damaged rice grains for hydrolysis was10% (50 °C, 150 rpm, 120h). After enzymatic hydrolysis of damaged rice, the obtained hydrolysate was used as a substrate in fermentation process with waste brewer`s yeast S. cerevisiae(2% of inoculum).After 24 hours of fermentation at 30 °C 0.95% of ethanol was obtained. Theresults obtained in this study showed that agro-industrial wastes could be used as substrate for enzymes production and enzymatic hydrolysis. Among tested waste materials, damaged rice grains are the most suitable for bioethanol production.