P1: Effect of Liquefaction Temperature on Glucose Yield from Sorghum in the Hydrolysis Pretreatment of the Biofuel Production Process

Sorghum is a starch-containing plant that is expected to become a valuable bioenergy crop in the near future because of its durability and limited growth needs. However, before it can be useful, the enzymatic processes used to produce ethanol from sorghum starch still needs to be optimized to yield a maximum amount of ethanol at a minimum energy cost. Maximizing the glucose yield from the hydrolysis pretreatment steps, liquefaction and saccharification, maximizes the ethanol yield from fermentation. Our investigation focused on varying the temperature of liquefaction, running the reaction at two temperatures. For liquefaction an α-amylase from Bacillus lichenformis and Aspergillus oryzae was used to run the enzymatic reaction at 85^oC and 25^oC respectively. The reaction yielded a diminished glucose concentration at the lower temperature; however, the theoretical 81.5 kJ/reaction of energy saved from running a reaction 60^oC lower could potentially compensate for differences in glucose yield. For a starting substrate of 28% (w/v) sorghum in water, hydrolysis run with liquefaction at 85^oC yielded an average glucose concentration of 27.9 g/L, three times larger than the average glucose concentration of hydrolysis run with liquefaction at 25^oC, 9.1 g/L. At these conditions, the glucose yield from liquefaction at 85^oC is able to provide enough additional ethanol to offset the energy cost of heating to the high temperature.