Ethanol production from different medium compositions of rice husk hydrolysate by using Scheffersomyces stipitis in a repeated-batch biofilm reactor and its modeling

This study aimed to generate ethanol from the detoxified/enriched rice husk hydrolysate (RHH) using Scheffersomyces stipitis in biofilm reactor (BR) and to predict experimental data using models. All fermentation media were supplemented with yeast extract (YE, 1%, w/v), and peptone (PE, 2%, w/v). To construct a plastic composite support-biofilm reactor (PCS-BR), PCS including polypropylene (50 %), soybean hulls (35 %), soybean flours (5%), YE (5%), bovine albumin (5%), and some minerals was selected. Results showed that best carbon source compositions were Medium C (50 % RHH (0.75-L) and 50 % glucose (0.75-L)) and Medium F (75 % RHH (1.125-L) and 25 % xylose (0.375-L). Ethanol yield (YP/S), theoretical YP/S (?), and ethanol concentration were 41.75 and 38.22 %, 81.70 and 74.79 %, and 5.16 and 3.80 g/L in Media C and F, respectively. Regarding the effect of nitrogen sources, the PE (41.75 % YP/S, 81.70 %, and 5.16 g/L) was the best compared to beef extract (40.25 %, 78.77 %, and 4.34 g/L) and NH4NO3 (31.67 %. 61.98 %, and 4.77 g/L). Best models for biomass production in Media C and F were Fitzhugh and Morgan-Mercer-Flodin models, respectively, which also fit-well the experimental ethanol production and substrate consumption data. Consequently, PCS-BR can be used to produce ethanol from RHH for a long-time (57 days).