Isolation and characterization of Weissella strains from soy sauce moromi mash

Abstract:

[Background] Weissella exists widely in fermented foods. Strains of this genera are involved in fermentation and contribute to the formation of volatile compounds. In soy sauce moromi mash, Weissella is the dominant genera of bacteria. Thus, it is of great importance to characterize their adaption to the environment, as well as properties related to soy sauce fermentation. [Objective] To isolate the main species of Weissella from soy sauce moromi mash, and evaluate their function for soy sauce fermentation by analyzing the dynamic composition of each species and their adaptation to the environment. [Methods] Characteristics of Weissella and their effect on the safety of soy sauce and fermentation process were evaluated by detection of quantity of Weissella during soy sauce fermentation, and their capability in production of short chain fatty acids, extracellular polysaccharides, biogenic amines (BA) and ethyl carbamate or their precursors. [Results] A total of 16 strains of Weissella, including Weissella confusa, Weissella paramesenteroides and Weissella cibaria, were isolated from soy sauce moromi mash. W. paramesenteroides was found to be tolerant to salt stress that confers the main species of Weissella in the moromi mash. The capability of short chain fatty acids synthesis of W. paramesenteroides is higher than that of W. confusa and W. cibaria. Production of toxic ammonia compounds are diverse for Weissella strains. Some strains of W. paramesenteroides produce more than one BAs and accumulate citrulline, the precursor of ethyl carbamate, while W. cibaria degrades a variety of BAs. [Conclusion] The tolerance of Weissella isolated from soy sauce moromi mash to salt stress, their growth at temperature lower than the optimal one, and their metabolisms were disclosed. This is important to elucidate the function and characteristics of Weissella for soy sauce fermentation and safety control in processing