This work investigated the effect of lipase addition on a Chinese traditional fermented fish product, Suanzhayu. The accumulation of lactic acid and the decrease of pH during the fermentation were mainly caused by the metabolism of Lactobacillus. The addition of lipase had little effect on pH and the bacterial community structure but promoted the growth of Proteus. The addition of lipase promotes the formation of volatile compounds, especially aldehydes and esters. The formation of volatile compounds is mainly divided into three stages, and lipase had accelerated the fermentation process. Lactobacillus, Enterococcus and Proteus played an important role not only in inhibition of the growth of Escherichia-Shigella, but also in the formation of flavor. This study provides a rapid fermentation method for the Suanzhayu process.

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In this study, three Lactiplantibacillus plantarum, namely 3-14-LJ, M22, and MB1, with high acetate esterase activity, acid, salt, and high-temperature tolerance were selected from 708 strains isolated from fermented food. Then, L. plantarum strains MB1, M22, and 3-14-LJ were inoculated at 107 CFU/mL in the model and 107 CFU/g in actual Suanzhayu systems, and the effects during fermentation on the physicochemical properties, amino acid, and volatile substance were investigated. The results showed that the inoculated group had a faster pH decrease, lower protein content, higher TCA-soluble peptides, and total amino acid contents than the control group in both systems (p < 0.05). Inoculation was also found to increase the production of volatile compounds, particularly esters, improve the sour taste, and decrease the bitterness of the product (p < 0.05). L. plantarum M22 was more effective than the other two strains in stimulating the production of isoamyl acetate, ethyl hexanoate, and ethyl octanoate. However, differences were discovered between the strains as well as between the model and the actual systems. Overall, the isolated strains, particularly L. plantarum M22, have good fermentation characteristics and have the potential to become excellent Suanzhayu fermenters in the future.