[Construction and composition diversity of a lactic acid bacterial community SFC-2]

To obtain the community that could accelerate the fermentation of the air-dried crop straws, a lactic acid bacteria community SFC-2 was constructed from the natural fermented products of the corn straw and rice straw by continuous restricted subcultivation in the MRS-S broth. The SFC-2 could lower the pH of the broth quickly, and produce high amount of lactic acid. The microbial composition of the SFC-2 became stable from the 25th generation according to the results of denaturing gradient gel electrophoresis (DGGE). The pH value of the SFC-2 dropped to 3.8 and the amount of lactic acid reached 10.64 mg x mL(-1) after 12 h cultivation in the broth, which contained 64% L-(+) lactic acid. Using morphological methods, four strains were isolated from the SFC-2 and they all belonged to Lactobacillus. The closest species were L. fermentum, L. plantarum, L. paracasei and L. paracasei sub sp., respectively. At the same time, the composition of the SFC-2 was also analyzed by constructing 16S rDNA clone library. The results of 16S rDNA sequencing showed that the closest species of seven clones were mainly L. fermentum, L. plantarum and L. paracasei. In clone libraries, 76.3% belonged to L. fermentum, 20.3% belonged to L. plantarum and 3.4% belonged to L. paracasei.