Ethanol fermentation in biofilm reactor using batch and continuous systems from rice husk hyrolysate and defination of production by mathematical models

Nowadays, rapid growth in population and industrialization has led to a steady increase in world demand for ethanol, which is considered to be one of the bio-energy sources of fuel and in particular of high efficiency and low environmental impact. Lignocellulosic biomass is the most abundant and renewable carbon source emerging as a byproduct of many industrial processes and agricultural materials, and can simply be produced from some energy plants. Lignocellulosic materials are receiving increasing interest worldwide for bioethanol production. In this study ethanol production of rice husk hydrolyzate in biofilm reactor was carried out using Pichia stipitis ATCC 58784 and ATCC 58785. For this purpose, the selection of the support material to be used in the selection of the biofilm reactor has been made. Experiments were carried out at different rates for both microorganisms and the best carbon source compound was determined. As a result of this, "50% rice husk hydrolyzate + 50% glucose" was selected as the No. 1 nutrient and "75% rice husk hydrolyzate + 25% xylose" was selected as the 2nd nutritional supernatant. After all the kinetic parameters and results were examined at the end of the fermentation, P. stipitis ATCC 58785 strain was found to be more effective in the use of rice husk hydrolyzate in the fermentation medium. In addition, the effect of nitrogen source was examined and it was determined that the best nitrogen source pair was yeast extract and peptone. Fermentation was carried out in the continuous system after determining the most suitable carbon source content and nitrogen source type in the fermentation environment. It was determined that the product and biomass productivity values obtained from this study were higher than the batch fermentation. In addition, enrichment and sterilization processes have been found to be important in the biofilm reactor. Using the results obtained from the fermentation process and the calculated kinetic parameters (experimental data), 11 different mathematical models were modeled for ethanol production, biomass development and substrate consumption. For this purpose, MGM, MLM, MRM, Stannard, Weibull, MMF, Asymmetric, Baranyi, Huang, Fitzhugh and Cone models are used. The best model for sugar consumption is the Baranyi and Huang models, while the best model is model Fitzhugh for experimental data of biomass development and ethanol production for medium number 1. While the best models for modeling experimental data of both cell growth and sugar consumption for medium number 2 were MMF and Cone models, the most successful models for ethanol production were MGM and MRM. The results have shown that rice husk hydrolyzate may be a potential carbon source in the fermentation medium.