High-gravity (HG) fermentation is a pivotal strategy for enhancing bioethanol concentration and reducing distillation costs. However, maintaining cell viability and fermentation efficiency over multiple cycles remains a significant challenge during scale-up. This study investigates the performance and operational stability of Saccharomyces cerevisiae immobilized in calcium alginate beads for HG glucose fermentation. The system was evaluated across 13 repeated batch cycles in both laboratory-scale and a 2-L bench-scale Stirred-Tank Bioreactor (STR). Results demonstrated that the immobilized system achieved peak performance at an initial glucose concentration of 172 g/L, maintaining a remarkably stable ethanol yield of 86.74% and a volumetric productivity of 0.40 g/L·h throughout 13 cycles. While scaling up to the 2-L STR introduced hydrodynamic shear, the beads maintained excellent mechanical integrity and consistent metabolic activity. The findings highlight the robustness of the immobilized cell system for continuous industrial applications, providing a reliable framework for large-scale HG bioethanol production without compromising yield over extended operations. • Stable bioethanol production at 172 g/L glucose via high-gravity fermentation. • Immobilized S. cerevisiae maintained a high yield (86.74%) over 13 repeated cycles. • Consistent volumetric productivity of 0.40 g/L·h achieved in a 2-L STR scale-up. • Ca-alginate beads showed excellent mechanical integrity against impeller shear. • Robust process stability demonstrated for long-term industrial ethanol production.
Damayanti et al. (Wed,) studied this question.