Atchara Nuphet, Duangporn Kantachote, and Wilawan Charernjiratrakul

pp. 659 - 670

Abstract

Total of 327 strains of lactic acid bacteria were isolated from 179 samples of various Thai fermented
foods. The strains were investigated for their probiotic properties based on stability in bile salt (0.15%) and
high acidity (pH 2, 3 and 4). Moreover, utilization of protein or fat or starch, growth in the absence of vitamin
B12 and growth under both aerobic and anaerobic conditions with no significant difference were also considered. According to the above criteria, 67 strains were selected for antibiotics sensitivity test. The selected
strains were susceptible to following antibiotics: ampicillin, cephalothin, cefoperazone, tetracycline and
chloramphenicol; however the strains were resistant to vancomycin, kanamycin, streptomycin, norfloxacin
and polymyxin B. Using agar spot method, only 5 strains were able to inhibit 13 strains of manifest by a
bacteria indicator as clear zone greater than 10 mm. A further investigation using co-culture technique
showed inhibition of the tested organisms was between 80 and 100 percent. The strains grew under media of
MRS and SPY2 (no materials from animal) over 36 hours with no significant difference. The strains were
investigated for survival in condition of high acidity within 3 hours. It was found that at pH 4 almost 100%
were maintained but at pH 2 and 3 the survival reduced approximately 1 log cycle. The strain LA71 which
showed the highest survival was identified as Lactobacillus plantarum.