Isolation and Characteristics of Histamine-producing Bacteria from Pickled Wax Gourd in East Zhejiang
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Abstract:
Selective culture and high-performance liquid chromatography (HPLC) screening were performed to study histamine production by bacteria in the traditional fermentation system of pickled wax gourd from Eastern Zhejiang. Histamine-producing strains were identified by 16S ribosomal DNA (rDNA), and histamine production capacity of each strain was determined. Additionally, the effects of temperature, pH, and salinity on bacterial growth and histamine production were investigated. The results showed that all five strains obtained from the early- and mid-fermentation stages belonged to two species, designated as M1 and M3, from the genus Enterobacter and showed close genetic relationships with E. aerogenes and E. xiangfangensis, respectively. The optimum growth temperature and pH for the two strains were 30 ℃and 7, respectively. The growth of the strains was stable at salinity below 5%. In the histamine fermentation medium, pH 4 was found to be optimum for histamine production by both strains. In the temperature range (20 ℃~35 ℃) suitable for bacterial growth, the optimum temperature for histamine production was 35 ℃. The yield of histamine decreased with increasing salinity. Under optimal conditions, values for maximum bacterial growth shown by M1 and M3 were 11.65 and 14.30 log CFU/mL, while values for maximum histamine production were 35.66 and 39.54 mg/L, respectively. Thus, these results provide a reference for processing and quality control of pickled wax gourd from Eastern Zhejiang.
