Cultivation And Identification Of Lactobacillus Curvatus HB02 And Its Biological Characteristics

Lactic acid bacteria HB02, cultured on doubled-layered agar or in liquid anaerobic enrichment cultivation mediumm, grew and produced acid rapidly. The bacterium was Gram-positive, non-sporeforming bacillus , compatibly anaerobic .The strain was identified to lactobacillus species by PCR with 16S rRNA-targeted primers. Furthermore, the strain was certainly confirmed as lactobacillus curvatus by amplification the species-specific sequences of lactobacillus 16S-23S rRNA intergenic spacer regions (ISR) containing its flanking 16S rRNA and 23S rRNA, and sequence analysis of the long ISR in GenBank.Lactobacillus curvatus HB02 was inoculated into MRS medium and incubated aerobicly at 37℃ for 24 h. The content of volatile fatty acid measured by gas chromatography was acetic acid 51.75 m mol/L, propionic acid 0.77 m mol/L, butyric acid 0.37 m mol/L ,and lactic acid measured by colorimetry was 28.06 m mol/L. The inhibition effect of HB02 on pathogenic bacteria such as Salmonella from rabits , Staphylococcus aureus, Escherichia coli from chincken and bovine was carried by co-culture of HB02 with the pathogenic bacteria for 24 h in liquid medium and the inhibition accuracy was detected by counting on certain selective solid medium. The result suggested that the inhibition effect was notable.To study the effect of Lactobacillus curvatus and some food micro-organisms on the growth and toxin production of fungi, a spore suspension of fungi was inoculated into MRS medium containing Lactobacillus spp. and incubated at 28℃ for 15 d. Lactobacillus curvatus cell in MRS medium totally inhibited the growth of mold and the production of aflatoxin Bl by mold. A spore suspension containing of fungi were inoculated into PYG medium with an initial pH of 3.0, 4.0, and 5.0 adjusted by lactic acid and incubated at 28℃ for 15 d. The pH of the medium ,weight of mycelium and aflatoxin Bl production were determined after 3, 6, 9, 12, 15 d of incubation. The cultured mixtures at initial pH of 3.0, 4.0, 5.0 produced more aflatoxin Bl, and had no effect on production of mycelium.This paper suggested that the preventive effect on growth and aflatoxin production was relative to a pH effect and microbial competition. And lactic acid had a stimulatory effect on production of aflatoxin Bl at pH 3.0~5.0.