| dc.description.abstract | Kveik yeast, a strain of S. cerevisiae originating from Norwegian brewing, exhibits thermotolerance, contributing to rapid fermentation within 24-48 hours, and can withstand stressful conditions. This thesis investigated various aspects of four selected kveik yeast strains, including their potential for bioethanol production, by analysing their thermotolerance, sugar conversion efficiency, and fermentation efficiency. The study employs batch and continuous fermentation methods for ethanol concentration, glucose conversion, productivity, yield, and overall efficiency. The research focuses on kveik yeast and examines critical parameters such as temperature, glucose concentration, inoculum size, and fermentation time. It uses predictive modelling techniques such as the design of experiments (DoE) and contour plot methodologies to optimize ethanol production using kveik Ebbegarden (Y9).
The batch fermentation model facilitated fermentation using the syringe piston expansion method. Following the Design of Experiments (DoE) analysis guided by the contour plot, ethanol production reached 48.04 g/l with an initial glucose concentration of 80 g/l at 40°C. This was achieved after 24-48 hours of fermentation using suspended cells. Similarly, the continuous fermentation model employed alginate bead immobilization within a Continuous Flow Stirred Tank Reactor (CFSTR). Under these conditions, ethanol production was 21.95 g/l with an initial glucose concentration of 56 g/l at a dilution rate of 0.34 /h. This fermentation process lasted 3-4 hours.
The findings revealed that temperature and initial glucose concentration significantly impact ethanol production. Additionally, the study shows differences in sugar conversion, ethanol concentration, yield, and productivity between batch fermentation with suspended cells and continuous fermentation with immobilized cells. Although the ethanol production and yield of immobilized cells are lower than those of suspended cells, continuous fermentation with immobilized cells achieves a significantly higher ethanol production rate per hour. The study concludes that kveik yeast is suitable for bioethanol production, especially in warmer conditions, due to its high-temperature tolerance and fast fermentation rate. Furthermore, Immobilized kveik yeast can increase efficiency and economic benefits in industrial applications by allowing for the reuse of yeast beads for over ten cycles, resulting in shorter fermentation times of 3-4 hours. | |
