29G-21 |
Screening and characterization of the spore-forming lactic acid bacteria in Taiwan |
W. H. CHUNG, C. Y. Cheng, and C. C. Liao. Bioresource Collection & Research Center, Food Industry Research & Development Institute, PO Box 246, HsinChu, 30052, Taiwan The survival rate of postprandial lactic acid bacteria(LAB)in the gastric tract is extremely low in stomach acid and bile salts. In addition, heat-labile and the dryness-sensitivity of LAB are major drawbacks for food processing. Research has been recently focused on spore-forming LAB for its better resistance to heat and dryness compared to LAB. This project was conducted to: (1) screen the local spore forming LAB (in particular, the geuns Sporolactobacillus), (2) establish a screening method of the possible isolates, and (3) determine the property of the spore forming LAB. Among the isolates screened by MRS and GYP, four spore forming LAB were isolated from 106 food or soil samples. Isolates were then characterized to genus Sporolactobacillus by their morphological, biochemical, and physiological properties. Furthermore, an isolate may belong to Sporolactobacillus inulinus based on the results of Micro ID, Biolog system, and 16s rDNA tests. In order to screen the strain that may be tolerant to acid, bile salt, and heat, spores were collected and tested. Spore suspensions with concentrations of 103 cfu /mL were spiked in solutions of pH 2 and pH 7, respectively and incubated at 37¢XC for 2h. Total plate counts showed that the cell numbers were similar whether they were incubated in pH 2 or pH 7 solutions. This result indicates the spores are acid-tolerant. In addition, spores of the isolate were able to increase from 106 to 108 cfu /mL when incubated in MRS broth amended with 0.3%(w/v) oxgall at 37¢XC for 24 hours. Results show the isolate was 0.3%(w/v) bile salt-tolerant. To the heat-tolerant test, the average of the D (decimal reduction times) values was 81.2 min at 75¢XC, 42.8 min at 80¢XC, 10 min at 85¢XC, and 7.1 min at 90¢XC. The Z value was 18¢XC.
Session 29G, Food Microbiology: General
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