Use of immobilized S. cerevisiae in beads made from polyvinyl alcohol and palm oil fuel ash to enhance ethanol production from a distillery wastewater

Abstract

© 2018, Thai Society of Higher Eduation Institutes on Environment. All rights reserved. The purpose of this study was to use an immobilized yeast culture (S. cerevisiae) to explore the potential to produce ethanol by fermenting a distillery wastewater either in batch or continuous -flow reactors.The beads were made using a mixture of polyvinyl alcohol (PVA) and palm oil fuel ash (POFA)in order to enhance the beads’ potential use. Results revealed that a 50% (v/v) cell concentration in the beads appeared to be the most suitable, while a PVA to POFA ratio of 10:3 (i.e. the highest POFA content investigated) was superior with respect to bead physical characteristics and performance, which was also validated by photomicroscopic images. The yeast cells were grown on both the outer and inner surface, especially at the cell concentration of 50% (v/v). Regarding the combined effect of PVA:POFA ratio and initial cell dry weight, a slight improvement in ethanol productivity (g/L/h) and ethanol yield (g/g) was observed with an increase in the POFA content and initial cell dry weight. Furthermore, ethanol productivity was significantly higher in a series of batch reactors operated at an HRT of 6 h compared to HRTs of 12 and 24 h; however, the effect of HRT variation on ethanol yield was less pronounced. Lastly, the continuous-flow system was moderately more efficient to remove total sugar than the batch system of about 17.3%, operated at the same HRT of 6 h.