Novel starter cultures Virgibacillus spp. selected from grasshopper sub shrimp paste to inhibit biogenic amines accumulation

Abstract

Controlling the content of biogenic amines (BAs) is critical to guarantee the safety of fermented aquatic products. The degradation characteristics and application potential of amine-negative starter cultures (Virgibacillus halodenitrificans CGMCC 1.18601: G25, Virgibacillus pantothenticus CGMCC 1.18602: G38) screened from grasshopper sub shrimp paste (Gssp) were studied. The enzymes of the two strains G25 and G38 that degrade BAs were amine oxidases (AOs) located on their respective cell membranes. The conditions that promoted the AO activity of Virgibacillus spp. were NaCl concentrations 5-10%, temperature 37 °C, pH 7.0 and ethanol concentrations 0-2%. Safety assessments (antibiotic susceptibility, biofilm activity and hemolytic activity) indicated that Virgibacillus spp. do not present a risk to human health, and this isolate can be confidently recommended as safe starter cultures for the food industry. Then, the two strains were cultured separately as starters and applied to the Gssp to analyze their influence on the flavor and quality of the product. As far as the bad flavors in Gssp such as sulfur-organic and sulf-chlor were concerned, the response values in the starter groups by G25 and G38 were significantly reduced by 39% and 65%, respectively. For the ability of strains to degrade BAs in Gssp, G25 degraded 11.1% of histamine, 11.3% of tyramine, 15.5% of putrescine and 4.1% of cadaverine; G38 significantly degraded 10.1% of histamine, 21.8% of tyramine, 18.1% of putrescine and 5.0% of cadaverine. These results indicated that the selected species could be used as starter cultures for the control of BA accumulation and degradation in Gssp.

Keywords: Amine oxidases; Degradation of biogenic amines; Grasshopper sub shrimp paste; Safety assessment; Starter cultures.

Fig. 1

Screening of BA-degrading strains in Gssp (the numbers in the figure are the order of the strains): a Decarboxylase activity, negative reaction: yellow, the negative control (NC) is a medium without any bacterial cells; positive reaction: purple, the positive control (PC) strain is Bacillus clausii. b AO activity. c Evaluation of BA degradability, data are the means ± standard deviations from three determinations

Fig. 2

Degradation of BAs under different conditions, data are the means ± standard deviations from three determinations: a NaCl concentration. b Temperature. c pH. d Ethanol concentration

Fig. 3

Degradation characteristics of biogenic amines, data are the means ± standard deviations from three determinations: (a) Ways the strains degrade BAs (b) Localization of the AOs

Fig. 4

Hemolytic activity. From left to right, the positive control: Bacillus Zhangzhouensis, G25, G38

Fig. 5

Application analysis of BA-degrading strains, data are the means ± standard deviations from three determinations: a Degradation of BAs in Gssp by strains. b Effects of strains on the flavor of Gssp

Fig. 6

Degradation of BAs in other fermentation products by strains, data are the means ± standard deviations from three determinations: a Degradation of BAs in cheese by strains. b Degradation of BAs in natto by strains