Reaction pattern of a novel thermostable α-amylase

A novel thermostable α-amylase, D45 was studied for its reaction pattern on starch hydrolysis. Fine structures of the dextrins and oligosaccharides produced by D45 were determined and compared with those produced by other thermostable α-amylases, Termamyl®LC (LC) and Termamyl®SC (SC). Waxy maize starch dispersion was hydrolyzed with LC, SC and D45 at different concentrations to obtain hydrolysates with the same dextrose equivalent value (DE). At DE ∼13, molecular weight distribution of dextrins produced by D45 displayed a mono-distribution with a peak centered at degree of polymerization (DP) of 7, whereas LC and SC hydrolysates displayed a bimodal-distribution of the molecular weight profiles with one peak centered at DP 5 and the other at DP 34. Thin-layer chromatograms (TLC) showed that DP 2, 3, 5, 6 and 7 were the primary oligosaccharides produced in LC hydrolysate, DP 4–7 in SC hydrolysate, and DP 6–9 in D45 hydrolysate. Comparison of the decrease in the blue color of amylose-iodine complex at 620 nm (blue value) with the increase in reducing value for the hydrolysis of amylose by LC, SC and D45 showed that for an equivalent decrease in blue value, LC and SC produced a higher percentage of reducing sugar than did D45. The results suggest that D45 has a greater degree of random attack (multichain) reaction, whereas LC and SC have more multiple-attack reactions.