Optimization and scale-up of ethanol production by a flocculent yeast using cashew apple juice as feedstock

Abstract

Biofuels have been gaining more space in the global energy sector, with special attention to ethanol, which has shown growing demand. Ethanol is a potential and promising alternative fuel due to the use of abundant renewable sources and its combustion characteristics. From this scenario, this research aimed to optimize ethanol production by a flocculant Saccharomyces cerevisiae CCA008 using cashew apple juice (CAJ) as feedstock. The alcoholic fermentation of CAJ was influenced for all evaluated variables (inoculum and substrate concentration, temperature, and agitation) and statistical models were successfully applied to describe the interaction between these variables and to optimize the operating conditions. The optimum conditions were initial substrate concentration (S0) of 102 g L−1, inoculum concentration (X0) of 5 g L−1, temperature (T) and agitation (Agit) settings at 34 °C and 140 rpm, respectively. Last, but not least, the scale-up of ethanol production was carried out using the predicted optimum operating conditions, the fluid dynamics characteristics and applying the best scale-up criterion (power per unit of volume). The efficiencies of the processes (on bench and pilot-scale) were not significantly different and high efficiencies (96.6–98.2%) were achieved, demonstrating satisfactory results. Moreover, maximum ethanol concentration (Pmax), YP/S and productivity (QP) did not vary significatively when the process was scaled-up. On the pilot-scale, Pmax, YP/S and QP were 49.2 ± 2.2 g L−1, 0.493 ± 0.00 g g−1 and 5.0 ± 0.2 g L−1 h−1, respectively. Therefore, ethanol could be efficiently produced by the fermentation of CAJ using the flocculent yeast S. cerevisiae CCA008 and the process could be easily scaled up.