초록
<P>While knowing the amylolysis mechanism is important to effectively decompose corn starch fed into an anaerobic digestor, the objective of this study was to detect the activities and locations of α-amylase in a continuous reactor and batch cultures. In the continuous reactor operated at 35 °C, the greatest cell-bound α-amylase activity was found to be 4.7 CU mL<SUP>−1</SUP> at hydraulic retention time (HRT) = 9 h, while the greatest volumetric hydrogen production rate (<I>r</I> <SUB>H2</SUB>) was observed at HRT = 3 h as 61 mmol L<SUP>−1</SUP> day<SUP>−1</SUP>. In the batch tests, the cell-bound α-amylase activities increased when the carbohydrate concentration decreased, and no significant reducing sugar accumulation was found in the serum bottles. By examining the specific hydrogen production rate (<I>q</I> <SUB>H2</SUB>) against different corn starch concentrations, the half-saturation constant (<I>K</I> <SUB>Sta</SUB>) and the maximum <I>q</I> <SUB>H2</SUB> were regressed to be 0.47 g L<SUP>−1</SUP> and 6 mmol g-VSS<SUP>−1</SUP> d<SUP>−1</SUP>, respectively. The electronic microscopic images showed that the microbes could colonize on the starch granules without the disturbance of any floc-like materials. Conclusively, by excluding the methanogens and floc matrix, the secreted <I>α</I>-amylases are predominately bound on the cell surfaces and enabled the microbial cells favorably attach on large substrates for hydrolysis under the mesophilic condition.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The α-amylase was found to be predominately cell-surfaces bound. </LI> <LI> The α-amylase activities were impaired due to short HRT in the continuous culture. </LI> <LI> The starch hydrolyzing rate slower than the reducing sugar uptake rate was evidenced by kinetic analyses. </LI> <LI> The microscopic images showed the morphologies of starch granules with microbes attachment. </LI> </UL> </P>