Endogenous and Exogenous Enzyme Effects on Different Breeding Clones of Sweetpotato (Ipomoea batatas Lam.) Roots Starch in Ethanol Production
Keywords:
sweetpotato, enzyme, saccharificationAbstract
The research described herein compares ethanol yield from the conversion of starch in sweetpotato storage roots via endogenous enzyme hydrolysis to that of exogenous enzyme hydrolysis (diastatic barley malt). White-fleshed roots of sweetpotato (Ipomoea batatas Lam) breeding clones; TU090R0005, TIB4004, TU090020, TU090013, BM8342197-05, BM854219905 and TIB4085 were processed for distillation to determine ethanol concentration. HPLC analysis was used to determine ethanol and residual sugar concentrations and 1H NMR analysis was used to confirm the identity of the distillate. HPLC analysis of the crude fermented slurry showed glucose at retention time of 9.98 min, ethanol at 21.50 min and a trace amount of residual glucose in TU090013. Initial glucose concentration (HPLC) ranged from 9.1±0.49 mg/mL to 12.3±0.49 mg/mL and 0.79±0.49 mg/mL to 3.46±0.49 mg/mL for exogenous and endogenous enzyme hydrolysis respectively. The volume fraction of ethanol as measured by HPLC ranged from 3.38 ± 0.06 % to 4.13 ± 0.06 % ; and 0.98 ± 0.06 % to 1.60 ± 0.06 % ; whereas the volume fraction by distillation, when compared to the HPLC data, ranged from 3.21 ± 0.14 % to 4.22 ± 0.14 %; and 0.86 ± 0.14 % to 1.64 ± 0.14 %. These results suggest that exogenous enzymes are needed for commercial production of ethanol. T-test (p < 0.05) comparing the amount of ethanol recovered after distillation and the concentration of ethanol measured by HPLC found no significant difference between the two methods for determining ethanol concentration.
Keywords: sweetpotato, enzyme, saccharification
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