Screening of Lactiplantibacillus plantarum with High Stress Tolerance and High Esterase Activity and Their Effect on Promoting Protein Metabolism and Flavor Formation in Suanzhayu, a Chinese Fermented Fish

Abstract

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.

Keywords: Lactiplantibacillus plantarum; esters; fermented fish; protein metabolism; starter culture; volatile compounds.

Figure 1

Strain screening result. (A) Venn diagram of the top 80 high-temperature-resistant strains, the top 80 salt-tolerant strains, the top 80 acid-resistant strains, and the top 80 strains of esterase activity. (B) Results for esterase activity against p-nitrophenyl acetate in the selected 15 strains. Letters “a–h” indicate the significant difference. (p < 0.05).

Figure 2

Hierarchical clustering of volatile compounds in model system (A) and actual system (B) of Suanzhayu. Isoamyl acetate, ethyl hexanoate, and ethyl octanoate contents in model system (C) and actual system (D) of Suanzhayu. Letters “a–d” indicate the significant difference (p < 0.05). For abbreviations, see Table 1.

Figure 3

E-tongue analysis of samples from the model system (A) and actual system (C). The results of the sour characteristics and the bitterness characteristics of E-tongue in the model and actual system are represented in (B,D), respectively. Letters “a–e” indicate the significant difference (p < 0.05). For abbreviations, see Table 1.