Effect of medium supplementation on very high gravity bioethanol fermentation using sago hampas hydrolysate as a feedstock

Bioethanol fermentation under very high gravity (VHG) conditions by using sago hampas hydrolysate (SHH) supplemented with yeast extract as a fermentation medium has resulted in an incomplete metabolism of glucose, leading to relatively low bioethanol production in comparison to the theoretical titre. Therefore, additional supplementation of the fermentation medium is necessary to increase the yeast tolerance towards inhibitors and high concentration of glucose and bioethanol. This work investigates the effect of supplementing SHH media with various nutrients on bioethanol fermentation under VHG conditions. The nutrients included magnesium sulphate (0.12 g/L), urea (3 g/L), glutamic acid (5 g/L), and peptone (5 g/L). Our results showed that culture supplemented with peptone has significantly improved the yeast growth by 0.9-fold and glucose consumption efficiency by 10% compared to the control cultures. Besides that, the media formulation has also increased bioethanol production by 13%, with a maximum concentration of 126.20 ± 3.0 g/L. In general, the results suggest an improved formulation of fermentation medium consisting of SHH for bioethanol production under VHG conditions. These results will provide useful insights into the development of bioethanol production from sago-based feedstock in the future.