Potencial amilolítico do grão de milho maltado no processo de sacarificação do mesmo cereal

Abstract

The aim of this research was the production of maize malt and the evaluation of its use for alcohol production. The maize grain was allowed to germinate at 20ºC for five days. The amylolitic potential of malt was optimized through a Complete Factorial Planning 22 with three central points, where the study variables were the temperature of incubation and the substrate concentration [S]. The sacarification was performed through a Planning of Mixture with three central points, where the study variables were the malt concentration and [S] during six 6 hours. The fermentation was carried out using the best sacarification condition, in a five-liter reactor and a two-liter working volume. The pH was maintained at 4.5 – 5.0. The Brix was corrected to 14º. The sterile hydrolyzed product was inoculated with 5.0 g.L-1 Saccharomyces cerevisiae. The system was submitted to two hours of initial aeration (170 LO2.h-1) and kept at 30ºC. During the fermentation process, analyses were made to determine the cell concentrations (g.L-1), reducing sugars (mg.mL-1), alcohol (g.L-1) and ºBrix. The temperature of incubation and substrate concentration were significant factors (p<0.05) in the determination of the amylolytic potential under the conditions of study utilizing 20% of substrate and incubation at 70ºC. The central experiments with 50% malt presented the best kinetic parameters with a volumetric rate of ethanol formation of 2.81 gethanol.L-1.h-1, which correspond to 8.0 ºGL, and a substrate conversion in cells of 0.127gcells.gglucose-1.