THE SELECTION, IDENTIFICATION, AND CHARACTERIZATION OF THE GROWTH OF PROBIOTICS FROM INTESTINAL TRACT OF CHINESE SOFTSHELL TURTLE (TRIONYX SINENSIS)

The aim of this study was to isolate the potential probiotics and to identify their effects. Using spot inoculation as the first screening and the Oxford cup method as the second screening, we isolated a strain of bacterium, namely Dec-43, from the intestinal tract of Chinese softshell turtle (Trionyx sinensis). This strain had antagonistic effects on bacterial strains including Aeromonas hydrophila, A. sobria and A. caviae. The analysis in bacterial morphology, physiology, and biochemistry indicated that Dec-43 shared the same physiological and biochemical properties with Enterococcus faecium. We used universal primers to amplify the 16S rRNA gene with PCR, and obtained a segment of 1448 bp from the total genomic DNA of Dec-43. After the sequencing and the BLAST analysis of this segment we found that the homology between Dec-43 and E. faecium was 99%. These results suggested that the Dec-43 should be E. faecium. By conducting the single factor test we determined that the optimal growth temperature of Dec-43 was 36℃; the optimal salinity was 0.6%; the optimal initial pH was 7; the optimal growth inoculum size was 10%. Through the orthogonal experiment we also determined the proper carbon (glucose) and nitrogen (peptone) contents should be 15 and 10 g/L respectively.