Continuous production of ethanol in bed packed bioreactors with immobilized yeast cells on lignocellulosic waste

Abstract

The continuous processes with immobilized cells are a good alternative for improving the efficiency and the performance of alcoholic fermentations. Raw materials derived from agroindustrial waste and their usage for promising carries have recently been tested for the cell immobilization. In this work, we evaluated the continuous production of ethanol in bed packed reactors with yeast cells immobilized on lignocellulosic waste of wood shaving, cane bagasse, corn leave and corn cob. We used glucose as carbon source to establish the reference conditions and we made the fermentations with commercial sucrose. We also evaluated the glucose syrup obtained from cassava flour as alternative substrate. The experiments were performed on a laboratory level in column reactors of 250 mL. The cane bagasse was the material on which the highest amount of cells was immobilized. A value of 0.047 g Biomass/g Carrier (gX/gC) was obtained. For the fermentation performed with glucose, the productivity reached was 13.33 ± 1.5 g/L h. A similar value, 13.00 ± 0.02 g/L h was reached for the productivity of fermentation with sucrose. In the fermentations performed with glucose syrup, a higher amount of ethanol was obtained in the process that used corn cob as carrier. 31.99 ± 1.93 g/L of ethanol was produced and the productivity of 10.66 ± 0.64 g/L h was reached. The results obtained have allowed us establish the potential these lignocellulosic waste has as carriers for cell immobilization for the continuous production of ethanol, and the possibility of using the glucose syrup as alternative substrate.