Abstract:To solve the problem of high viscosity and difficult saccharification of extrued sorghum starch, an enzymatic extrusion liquefaction pretreatment was used. Differences between sorghum starches treated by enzymatic extrusion, conventional extrusion and cooking were studied and the ethanol yield of different fermentation methods was compared. Results showed the morphology of sorghum starch treated by enzymatic extrusion was most damaged. XRD data indicated the sorghum starches generated strong peaks of B-type crystallites at 22°, the crystallinity of sorghum starches treated by enzymatic extrusion, conventional extrusion and cooking were 6.96%, 10.89% and 9.53%. Sorghum starches tended to be more appropriate for fermentation because its extent of gelatinization was 99.36% and its peak viscosity was 163 cp. Semi-solid fermentation exhibited the highest fermentation efficiency of 92.23% among the different three fermentation methods. Based on Response surface methodology (RSM), the optimum extrusion conditions to obtain maximum fermentation efficiency of 93.73% were at the BT of 98.40℃, MC of 33.28%, and AC of 1.62‰.
