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For fuel alcohol production, enzymatic liquefaction and saccharification of tapioca starch by a-amylase and glucoamylase were studied. The thermophilic a-amylase Termamyl produced from Bacillus licheniformis gave a better liquefaction than the relatively low temperature enzyme BAN from B. subtilis. Optimal temperature and pH with Termamyl were 90-951C and 5.8, respectively. Minimal amount of Termamyl 240uc for a satisfactory liquefaction for a two-hour reaction was about 0.0125%(v/w) with respect to the mass of tapioca used. For saccharification experiments two enzymes, Novo AMG and Do- Il enzymes, were compared. The enzymatic activity of each enzyme was a little different depending on the substrate used and the latter was found to have a significant amount of a-amylase activity. With Novo AMG optimal temperature was about 58C. The pH optimum was 4.3 with maltose, howeve;with tapioca, no difference was observed between pH 4.3 and 5.7 which is a natural, unadjusted pH of liquefied tapioca. For 85% of completion of saccharification, it was necessary to use 0.0625% (v/w) of Novo AMG 400L for tapioca and to run the reaction for more than 10 hr. Packed volume of solid particles in tapioca slurry remained at around 30% during liquefaction and saccharification. This indicates that the removal of the solid particle before fermentation is not economically feasible at all, even though the solid particles make it very difficult to operate the bioreactor in a continuous mode with cell-recycle.
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