The influence of sorghum grain decortication on bioethanol production and quality of the distillers' dried grains with solubles using cold and conventional warm starch processing

Very high gravity hydrolysis-fermentation of whole and decorticated sorghum grains were compared using conventional and cold hydrolysis methods to assess the extent by which decortication could minimize enzymes dosages and affect the quality of the distillers' dried grains with solubles (DDGS). All processing configurations achieved ethanol concentrations between 126 and 132 g/L (16.0-16.7% v/v), although decortication resulted in a decreased ethanol yield. Decortication resulted in a decreased volumetric productivity during warm processing from 1.55 to 1.25 g L−1 h−1, whereas the required enzyme dosage for cold processing was decreased from 250 to 221 μl/100 gstarch. Cold processing decreased the average acid detergent fibre (ADF) from 35.59% to 29.32% and neutral detergent fibre (NDF) from 44.04% to 32.28% in the DDGS compared to the conventional (warm) processing. Due to lower enzyme requirements, the use of decorticated grains combined with cold processing presents a favourable process configuration and source of DDGS for non-ruminants.