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Amylolytic Lactic Acid Bactria (ALAB), a LAB strain that possesses amylolytic activity. It can be recovered from isolation sources of both plant and animal origins. This study focused on isolation of ALAB from plaa-som, a well-known fermented fish among the Northeasterners of Thailand. Cooked rice, a starch containing ingredient is considered as a major source to obtain ALAB strain from plaa-som. Fourteen plaa-som samples were collected around Khon Kaen, Roi Et, Petchaboon, and Yasothon provinces with pH, total acidity (TA), and fermentation time between 4.4-6.1, 0.04-0.48 %g/g, and 0-120 hrs. after fermentation, respectively. One hundred ALAB isolates were successfully isolated from plaa-som between 0 to 72 hrs. of fermentation, pH between 4.4-5.7, and TA between 0.12-0.48 %g/g. These isolates were initially recognized by their typical characteristics as LAB. These LAB isolates differed in starch hydrolysis and displayed different halo ratios on MRS-starch agar when they were exposed with iodine pellet. Based on the potency indices, these isolates can be divided into 3 groups including low, moderate, and high group with 65, 25, and 10 members, respectively. The majority of strains in high potency group (80%) produced high extracellular -amylase activity between 0.02 and 0.36 U/mL compared to cell bound -amylase activity. The highest activity of 0.36 U/mL was observed in isolate PJ75 isolated from plaa-som at 24 hrs of fermentation. This suggests that ALAB can be isolated from plaa-som between 0-72 hrs, particularly between 0-48 hrs that all ten isolates of the high potency group were isolated. Thus fermentation time of plaa-som is an influencing factor for the isolation of ALAB. Moreover, the potency index was also directly reflected the amylolytic activity among the isolates. |
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