Aplicação do arraste gasoso associado ao vácuo em fermentações extrativas utilizando matérias-primas sacarina e amilácea

Abstract

Despite being well-established industrially, ethanol fermentation is limited by the toxic effect of ethanol on yeast, resulting in wines with low alcohol content (10–15% v/v). Ethanol removal techniques can be applied to mitigate the inhibitory effect of the product and increase process productivity. In this context, the present work evaluated extractive ethanol fermentation using vacuum-assisted gas stripping. Initially, ethanol removal from hydroalcoholic solutions was investigated under different operational configurations of CO₂ specific flow rate, temperature, and pressure, with the aim of identifying the conditions that provided the highest ethanol removal from the liquid phase and the highest concentration in the gas phase. Subsequently, extractive fermentations with saccharine feedstock were assessed using both conventional and vacuum-assisted gas stripping, and the energy requirements of both processes were analyzed. Finally, extractive fermentations with starchy feedstock were conducted in separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes. Mathematical models were developed to describe the processes, based on mass balance equations and incorporating the kinetics of hydrolysis, fermentation, and ethanol and water removal. The results of ethanol removal from hydroalcoholic solutions showed that all three operational variables significantly affected the process within the evaluated experimental range. The application of the technique increased the ethanol concentration in the gas phase by up to six times. In extractive fermentations with saccharine feedstock, both vacuum-assisted and conventional gas stripping increased ethanol productivity by up to 14.3%. The energy analysis indicated that the integrated technique reduced energy demand by 31.3% compared to conventional gas stripping. Finally, extractive fermentation of starchy feedstock increased ethanol productivity by 60% compared to conventional fermentation. The mathematical model adequately described the fermentation process. Vacuum-assisted gas stripping demonstrated potential as a promising technique, with the capacity to enhance ethanol productivity and lower the costs associated with the recovery and concentration of the removed ethanol.