Characterization, enzymatic and biological properties of a dominant lactic acid bacteria strain of Lactobacillus sakei subsp. sakei isolated from stinky mandarin fish

Abstract

Presently in order to excavate suitability of resources of lactic acid bacteria for fermentation of mandarin fish, a strain of lactic acid bacteria (LAB), which was cultivated from stinky mandarin fish via using traditional MRS medium (CMC 1-8), was firstly isolated and purified. Subsequently, it was discovered that the as-harvested LAB was recognized as Lactobacillus sakei subsp. sakei with assistance of technology of phenotypic identifying and 16S rRNA sequencing. Concurrently, relevant characteristics in aspects of growth curve, acid production capacity, temperature and salt tolerance of Lactobacillus sakei subsp. sakei were plainly investigated. Furthermore, the preliminary research on protease properties and biological properties was revealed. The results unfolded that the strain could grow and produce acid normally at 37 °C, and deliver a strong tolerance even under 3% NaCl at 12 °C, which could be significant sufficiently to satisfy the low-temperature and salty fermentation of mandarin fish. The best compatible temperature and pH value for protease production were at 70 °C and 9.0, respectively. Resultantly, the main metabolites, containing polyphenols, flavonoids and soluble polypeptides, performed a remarkable effect on scavenging abilities of 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picrylhydrazine (DPPH) free radical and ferricyanide reducing ability, of which the IC₅₀ were 1.05, 6.87, and 4.62 mg/mL, respectively. And, the metabolites displayed partial inhibitory effects on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus subtilis. Therefore, CMC 1-8 can potentially serve as a functional microorganism to directionally ferment mandarin fish.

Keywords:
stinky mandarin fish; Lactobacillus sakei subsp. sakei; protease properties; metabolites; antioxidant activity