Continuous bioreactor bioprocess using immobilized Spathaspora passalidarum to convert hydrolysates of oat and soybean hulls into ethanol

Abstract

We investigated the performance of fluidized and packed-bed bioreactors using cells of Spathaspora passalidarum UFMG-CM-469 immobilized on LentiKats® in the fermentation of lignocellulosic biomass hydrolysates. Acid (AH-CYE) and enzymatic (EH-CYE) hydrolyses of a 1:1 mixture of oat and soybean hulls, minimally supplemented with crude yeast extract, were used as substrates. Continuous cultures at dilution rate (D) of 0.05 h−1 were run in the fluidized and packed-bed bioreactors, using both AH-CYE and EH-CYE, showing ethanol yields varying from 0.30 to 0.45 g•g−1 and productivities from 0.39 and 0.99 g•(L•h)−1. Continuous cultures in the fluidized bioreactor, which proved to be better than the packed bed, operating at higher dilution rates of 0.1 h−1 and 0.2 h−1 increased ethanol productivity, reaching 1.67 g•(L•h)−1 when using AH-CYE and 2.65 g•(L•h)−1 with EH-CYE. These results show the possibility of exploring the fermentation of lignocellulosic biomass hydrolysates in continuous cultures of immobilized S. passalidarum UFMG-CM-469 to produce second-generation ethanol under a concept of biorefinery.