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 (∼107 cells/mL). During the next 5–20 days of fermentation, the predominating bacteria were Weissella spp. (∼107–108 cells/mL). Lactobacillus spp. were a significant portion (∼106 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 (∼107 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. Practical Applications The microorganisms play an important role in the processing and preservation of pickled vegetable foods. The predominant species and its organic acids concentration in the fermentation process of pickled wax gourd were investigated using the 16S rDNA clone library technology combined with quantitative real-time polymerase chain reaction. This method can provide quicker information about the bacterial communities involved in traditional wax gourd fermentation and data regarding flavor formation of pickled vegetables. The formation of organic acids and antimicrobial activity by specific types of lactic acid bacteria may facilitate linking the microbial ecosystem of pickled wax gourd to quality control. It can also provide the microbial and theory identification for quality control of pickled wax gourd processing.