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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. [ABSTRACT FROM AUTHOR]

The bacterial profiles of 63 grasshopper sub shrimp paste samples collected from seven typical regions around the Bohai Sea were investigated by high-throughput sequencing. Tetragenococcus muriaticus was found to be the prevailing species present in all the samples, and the presence of T. muriaticus also weakly correlated with the histamine content in the samples. Six T. muriaticus strains with low biogenic amine (BA)-producing ability and deficient in histamine production were identified and subjected to safety assessment. All six strains displayed weak resistance to fifteen known antibiotics as based on the Enterococcus breakpoint values. None of the strains exhibited hemolytic activity or biofilm formation. All strains exhibited were able to grow on MRS agar containing 21% NaCl and expressed amine oxidase and strain-specific proteases and lipases. Most of the strains exhibited acid production at 18% NaCl. Moreover, three of the strains (designated as SG, TS, and QH) with histamine degradation ability were inoculated into separate shrimp paste samples to determine their effect on BA accumulation. The results indicated that the addition of T. muriaticus to shrimp pastes not only led to a significant reduction of BA content in the pastes but also improved the flavor of the pastes. Consequently, these strains may be used as potential candidates for controlling the content of histamine in fermented foods. [ABSTRACT FROM AUTHOR]

A Gram-positive, aerobic, motile and short rod-shaped bacterium, designated as strain G56T, was isolated from shrimp paste produced in Panjin, China. Grows in the presence of 1.0–25.0% (w/v) NaCl (optimum at 10%), pH 5.0–9.5 (optimally at 7.0) and 10–50 °C (optimally at 37 °C). Positive for catalase and oxidase activities, but lack the ability to reduce nitrate. Acids produce from d-ribose, d-xylose, d-galactose, glycerol and d-trehalose, but no acid is produced when salicin, d-mannose, d-cellobiose and l-sorbose are provided as substrates. The polar lipid extract is found to contain diphosphatidylglycerol, phosphatidylglycerol, an unknown glycolipid, and unidentified phospholipids. Fatty acids are mainly defined as anteiso-C15:0 (69.7%) and anteiso-C17:0 (23.3%). The G+C content of its DNA is 44.7 mol%. The draft genome of strain G56T is 3,209,087 bp in length and the average nucleotide identity value (ANI) and the digital DNA-DNA hybridization (DDH) values between strain G56T and L. juripiscarius JCM 12147T is 78.41% and 22.0%, respectively. Polyphasic taxonomic analysis classified strain G56T as a novel species in the genus Lentibacillus, and therefore, we named it as Lentibacillus panjinensis sp. nov.. [ABSTRACT FROM AUTHOR]

The presence of biogenic amines (BAs) in fermented foods represents a health risk for consumers. Therefore, understanding how BAs are accumulated would enable better control of their content in fermented foods. In this study, the BA profiles of grasshopper sub shrimp pastes produced in different typical regions (Panjin, Rongcheng, Shouguang, Dalian, Tangshan, Qinhuangdao and Yantai) around the Bohai Sea were evaluated. Among the microbial diversity found in the shrimp pastes, Tetragenococcus , Lactobacillus , Aspergillus and unclassified_k_Fungi were the predominant genera. The results of RDA correlations between physicochemical-microbial indexes and BAs suggested that the high BAs content in shrimp paste might be linked to the salinity of products and halophilic bacteria present in shrimp paste. A total of 442 strains of halophilic bacteria were identified and the five most abundant genera were Bacillus , Staphylococcus , Tetragenococcus , Virgibacillus and Oceanobacillus. Among these, 95.10% of species could produce BAs although their production appeared to vary greatly, with 30 strains considered as high producers, achieving a BA concentration of 787.54 ± 20.87 mg/kg. Thus, controlling these bacteria might be the key to controlling the BA content in the shrimp paste. • Complete profile of microbiota was evaluated and that had regional differences. • Types and contents of BAs varied among samples of seven typical regions in China. • Halophilic bacteria and salinity of samples may be main factors for high BA contents. • Salinity of the products at 20–25% would keep the BA contents within the safe limit. • 30 high-BA producing strains might be responsible for the accumulation of BAs. [ABSTRACT FROM AUTHOR]