关键词: 乳杆菌；籼米粉；淀粉酶；酶学特性

Abstract: In this paper, pure culture fermentation of indica rice flour slurry with three strains of Lactobacillus with the ability to degrade starch, L. acidophilus 14 (La), L. casei M (Lc) and L. plantarum 115 (Lp), was studied. It was found that all the strains had the ability to produce acid in fermented indica rice flour slurry, and the acid-producing ability at 12 h was in the decreasing order La > Lp > Lc. At the same time points, viable bacterial counts also followed this trend. The fastest increase in viable cell number and the strongest acid-producing capacity were observed for La from 4 h to 8 h, and for both Lc and Lp from 6 h to 10 h. The activities of amylases produced by the three strains (named La-a, Lc-a and Lp-a), followed the decreasing order: La-a > Lp-a > Lc-a. The maximum activity of La-a was 79.78 U/mL at 6 h, while the maximum activity of Lc-a and Lp-a was 51.89 and 68.77 U/mL at 8 h of fermentation, respectively. The three amylases were all neutral enzymes. The optimum temperatures of La-a, Lc-a and Lp-a were 55, 45 and 50 ℃, respectively, and the optimum pH values were 6, 7 and 6, respectively. The three amylases could not tolerate temperatures above 70 ℃, but Lp-a was relatively heat tolerant. Their pH stability was La-a > Lp-a > Lc-a. After fermentation, the total starch content in indica rice flour slurry decreased significantly, while the proportion of amylose in the total starch increased, indicating that a certain amount of isoamylase was produced during fermentation.

Key words: Lactobacillus; indica rice flour; amylase; enzymatic characteristics