Bioethanol production from mixed sugars at a semi-pilot scale through two-step repeated sequential fermentation

[Display omitted] •This strategy enables complete xylose conversion at higher mixed sugar concentrations.•The fermentation performance of high cell density sequential culture was assessed.•Maximum ethanol productivity: Glucose (6.92 g/L/h) and Xylose (2.28 g/L/h) were achieved.•Techno-economic analysis of sequential fermentation of bagasse hydrolysate was performed. Assessing the industrial suitability of sequential culture for efficient conversion of mixed sugars from plant biomass hydrolysate is essential. In the present study, a two-stage sequential fermentation of mixed sugar-rich sugar cane bagasse hydrolysate was performed to produce bioethanol. In the first stage, glucose fermentation using Z. mobilis was carried out, followed by xylose fermentation using S. stipitis in the second. However, xylose fermentation was done only after completely separating primary cells and residual ethanol. Sequential fermentation of mixed sugar-rich bagasse hydrolysate yielded an ethanol titer of 77.7 g.L−1 with an average ethanol yield of 0.48 g.g−1 and overall ethanol productivity of 1.38 g.L−1.h−1. Further, repeated sequential fermentation (RSF) of mixed sugars was performed for two cycles. RSF assessed the fermentation performance of high cell density sequential culture achieved through sequential cell recycling. The maximum ethanol productivity achieved from glucose and xylose was 6.92 g.L−1.h−1 and 2.28 g.L−1.h−1, respectively. In addition, a techno-economic analysis found that the minimum selling price of the ethanol (MSP) produced from sequential fermentation of mixed sugar-rich bagasse hydrolysate (scenario I) was up to 1.7 US$. L−1. On the other hand, the MSP calculated after omitting reagent costs of synthetic glucose and xylose of the first scenario was up to 0.52 US$. L−1.