Fate of free amino nitrogen during liquefaction and yeast fermentation of maize and sorghums differing in endosperm texture

Abstract

Biofuels demands have motivated the increasing research in production technology as well as effective raw material utilization. Fusel alcohol production had been related with the free amino nitrogen (FAN) content produced during hydrolyses stages and also as a stress response of Saccharomyces cerevisiae. This paper analyses the effect of grain type and endosperm texture on FAN production during starch liquefaction and yeast fermentation of maize, white and red sorghums bioconverted into ethanol. The white sorghum had a harder endosperm texture and upon milling produced a coarser granulation compared to the red counterpart. Therefore, the red sorghum produced higher amounts of FAN during liquefaction and the kinetics of these nitrogenous compounds were metabolized faster during the first hours of yeast fermentation. The white and red sorghums yielded 13.6% and 2.7% lower ethanol compared to the maize counterpart. The white sorghum yielded the lowest amount of ethanol likely to its relatively harder endosperm texture that was less susceptible to biocatalysis and yeast fermentation.