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Production of bioethanol from multiple waste streams of rice milling

Favaro, Lorenzo, Cagnin, Lorenzo, Basaglia, Marina, Pizzocchero, Valentino, van Zyl, Willem Heber, Casella, Sergio
Bioresource technology 2017 v.244 pp. 151-159
amylases, bioethanol, bioprocessing, ethanol, ethanol production, feedstocks, fermentation, fungi, genetically engineered microorganisms, lignocellulose, milling, milling byproducts, rice, rice bran, rice hulls, saccharification
This work describes the feasibility of using rice milling by-products as feedstock for bioethanol. Starch-rich residues (rice bran, broken, unripe and discolored rice) were individually fermented (20%w/v) through Consolidated Bioprocessing by two industrial engineered yeast secreting fungal amylases. Rice husk (20%w/v), mainly composed by lignocellulose, was pre-treated at 55°C with alkaline peroxide, saccharified through optimized dosages of commercial enzymes (Cellic® CTec2) and fermented by the recombinant strains.Finally, a blend of all the rice by-products, formulated as a mixture (20%w/v) according to their proportions at milling plants, were co-processed to ethanol by optimized pre-treatment, saccharification and fermentation by amylolytic strains.Fermenting efficiency for each by-product was high (above 88% of the theoretical) and further confirmed on the blend of residues (nearly 52g/L ethanol). These results demonstrated for the first time that the co-conversion of multiple waste streams is a promising option for second generation ethanol production.