An novel immobilization method of Saccharomyces cerevisiae to sorghum bagasse for ethanol production

Natural sorghum bagasse without any treatment was used to immobilize Saccharomyces cerevisiae at 0.6 ± 0.2 g dry cell weight (DCW)/g dry sorghum bagasse weight (DSW) through solid-state or semi-solid state incubation. The scanning electron microscopy (SEM) of the carriers revealed the friendship between yeast cells and sorghum bagasse are adsorption and embedding. The ethanol productivity of the immobilized cells was 2.24 times higher than the free cells. In repeated batch fermentation with an initial sugar concentration of 200 g/L, nearly 100% total sugar was consumed after 16 h. The ethanol yield and productivity were 4.9 g/g consumed sugar on average and 5.72 g/(L h), respectively. The immobilized cell reactor was operated over a period of 20 days without breakage of the carriers, while the free cell concentration in the effluent remained less than 5 g/L thoughout the fermentation. The maximum ethanol productivity of 16.68 g/(L h) appeared at the dilution rate of 0.3 h−1.