BACTERIA COMMUNITY ANALYSIS BY QUANTITATIVE REAL-TIME PCR OF FERMENTING WAX GOURD AND ITS CHANGES OF ORGANIC ACIDS

The bacterial communities and predominating species during the fermentation of wax gourd were investigated by using 16S rDNA clone library technology combined with a quantitative real-time polymerase chain reaction (qRT-PCR) method. At the beginning of wax gourd pickling, Acinetobacter spp. were the predominant bacteria (similar to 10(7) cells/mL). During the next 5-20 days of fermentation, the predominating bacteria were Weissella spp. (similar to 10(7)-10(8) cells/mL). Lactobacillus spp. were a significant portion (similar to 10(6) cells/mL) of the bacterial flora only at day 10 of the fermentation. At days 15 and 20 of fermentation, W. paramesenteroides was the main species (similar to 10(7) cells/mL), identified by using qRT-PCR. Lactic, citric and acetic acids levels were low at the beginning of fermentation and increased significantly (P < 0.05). The increase in lactic acid to 0.33 g/L at day 20 was likely to have occurred because of the sudden increase in W. paramesenteroides and Weissella spp. 5 days earlier.