Sirirat Seehanat, Lechai Budtacup, Somkhit Kangklang, and Vichai Leelavatcharamas

pp. 265 - 274

Abstract

The useful bacteria which were isolated from the gastrointestinal tract of freshwater prawn
(Macrobrachium rosenbergii de Man), cultivated in earthen pond at Maha Sarakham province, Thailand,
consisted of 14 isolates of Bacillus (B₁ – B₁₄) and 18 isolates of Lactic acid bacteria (LA₁ – LA₁₈). The
abilities of all isolated bacteria on growth inhibition of pathogenic bacteria (Escherichia coli, Bacillus
cereus, Aeromonas hydrophila and Pseudomonas aeruginosa) were studied by paperdisc plate method. The results showed that Bacillus B₂ and B₅ were unable to inhibit the growth of all of the tested
pathogens. Bacillus B₁, B₁₀ and B12 were capable of inhibiting the growth of 3 of 4 tested pathogen
strains. Although all of the isolated lactic acid bacteria (LA₁ –LA₁₈) could not inhibit the E. coli growth,
all of them could inhibit the growth of B. cereus. The isolated lactic acid bacteria which were capable
of inhibiting the growth of 3 tested pathogen strains (excluded E. coli) were LA₁₂ , LA₁₃ , LA₁₄ , LA₁₅ ,
LA₁₆ , LA₁₇ and LA₁₈. In order to select the high potential strain of bacteria for using as probiotics,
Bacillus B₁ , B₃ , B₄ , B₁₀ and B₁₂ and lactic acid bacteria LA₁₂ , LA₁₃ , LA₁₄ , LA₁₅ , LA₁₆ , LA₁₇ and LA₁₈
were tested for their growth abilities in various growth conditions. The tested growth conditions
included various concentrations of the bile salt and salt (NaCl) and various pH and temperatures.
The results revealed that Bacillus B₁ and B10 and lactic acid bacteria LA₁₃ , LA₁₆ and LA₁₈ exhibited
high potential for using as probiotics. The results of biochemical test for identification of these high
potential strains showed that Bacillus B₁ and B10 were possibly B. licheniformis and B. thuringiensis
respectively. The lactic acid bacteria LA₁₃ , LA₁₆ and LA₁₈ were possibly the same strain and belonged
to the genus Pediococcus.