Optimization of ethanol production from intermediate products of sugar beet technology. [Doctoral dissertation] | Оптимизација добијања етанола ферментацијом међупроизвода технологије прераде шећерне репе. Докторска дисертација

Research from the framework of this study included the examination of the course of fermentation of medium based on raw, thin and thick juice as intermediate products, and molasses as by-products of sugar beet processing by yeast Sacharomyces cerevisiae. The feasibility of ethanol production from raw, thin and thick juice and molasses from local sugar factories was experimentally confirmed in batch fermentation in a bioreactor of working volume 1.5 l. Important parameters for modeling of the process using response surface methodology were defined by analyzing the results of the course of fermentation of intermediate products of sugar beet processing. For description of the response function of the number of yeast cells, ethanol content and total sugar content during fermentation, the response function of the number of yeast cells, ethanol content and total sugar content during fermentation, the effects of initial sugar content in the range 5-25% w/v and duration of fermentation in the range 0-48 h were examined. Obtained models have contributed to a better understanding of the impact of different initial sugar content, fermentation time and interactions of these factors on the selected responses of the course of fermentation of culture media based on intermediate products of sugar beet processing. In addition, the goal of this work included the selection of the optimal values of the initial sugar content and duration of fermentation of raw, thin and thick juice and molasses applying the obtained second-degree polynomial models of the process. Optimal initial sugar content and fermentation time for ethanol production from raw juice were estimated to be 12.71% w/v and 38 h, respectively. For thin juice optimal values of varied parameters were the initial sugar content 12.75% w/v and fermentation time 42 h. The optimal values of initial sugar content and fermentation time for thick juice were defined to be 21.12% w/v and 47 h, respectively. For molasses were defined the following optimal values of varying parameters: the initial sugar content 11.59% w/v and fermentation time 34 h. Further research was performed with the aim of validation of the obtained results and confirmation of their applicability in the enlarged scale. The results obtained during the fermentation in bioreactor of working volume 10 l, under optimal conditions defined for fermentation in the bioreactor of working volume 1.5 l, were in good correlation.