Treatment of rye biomass by extrusion for production oligosaccharides and C6-C5 sugars for bioethanol by enzyme hydrolysis

Abstract

The extrusion process is important to stabilise the quality of cereal biomass, and especially from rye which is more sensitive for biodegradation in compare with other cereals. This process has been used for pre-treatment of rye biomass following by enzymatic hydrolysis using different commercial enzyme preparations for production of oligosaccharides and C6–C5 sugars subsequently processed to bioethanol. The extrusion treatment resulted in variations of rye starch crystallinity as well as the changes in solubility and water absorption related with significant chemical changes. Comparing the arabinose to xylose ratios of rye, it was noticed that there is no significant difference between extruded and natural cereals. On the contrary, a higher bioethanol yield in the distillate has been achieved by using extrusion pretreatment of raw material. The highest yield of tested sugars was achieved by using amylolytic and xylanolytic enzymes composition from Humicola and Bacillus spp. Trichoderma reesei. The used enzyme preparation also improved the quality of bioethanol by increasing the content of ethanol and decreasing the concentrations of propanol, isobutanol, isoamyl and amyl alcohols and the methanol concentration.