초록
<P>Physical factors that enhanced the production of raw starch degrading enzyme by a thermophilic filamentous bacterium, <I>Laceyella sacchari</I> LP175 in a 3 L airlift fermenter, were optimized at a pH of 6.5, a temperature of 45°C, and an aeration rate of 0.5 vvm using a central composite design. This yielded 278 U/mL, at 36 h cultivation, an increase in enzyme production and productivity of 1.53‐ and 2.04‐fold, respectively, as compared with a shaking flask cultivation. Raw starch degrading enzyme produced by <I>L. sacchari</I> LP175 with commercial glucoamylase synergistically enhanced the hydrolysis of 300 g/L dried cassava chips (71% starch content) to 157 g/L reducing sugars, equivalent to 66.3% hydrolysis at pH 6.5 and 50°C for 12 h. The comparative study on bioethanol production in a non‐sterile system from dried cassava chip by three different processes; the maximum production, 90.9 g/L (88% theoretical yield), was obtained by modified simultaneous saccharification and fermentation at 50°C for 6 h and subsequent fermentation by the thermotolerant <I>Kluyveromyces marxianus</I> DMKU‐KS07 at 42°C within 18 h with the highest productivity of 3.79 g/L/h. The other processes tested – separate hydrolysis and fermentation and simultaneous saccharification and fermentation – yielded 83 and 51.6 g/L of ethanol, respectively.</P>