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In this study, a myrosinase-producing strain named RJ35 was isolated from a rapeseed field soil, and it was identified by morphological and molecular biological methods. The myrosinase produced by strain RJ35 was purified by sequential ultrafiltration and gel filtration chromatography and its enzymatic properties were studied. Strain RJ35 was assigned to the genus Sphingobacter. The molecular mass of the myrosinase was about 100 kDa. The optimum pH and temperature of the myrosinase were 7.5 and 40 ℃, respectively. Moreover, metal ions had no significant activating effect on the myrosinase. The results of high performance liquid chromatography (HPLC) showed that this enzyme could hydrolyze radish seed extract to produce sulforaphane. Hydrolysis for 30 min under the optimum conditions resulted in a yield of sulforaphane of 5.95 mg/g (radish seed). These research results may lay an experimental foundation for the development of microbial myrosinase.

In order to evaluate the effect of Streptococcus thermophilus fermentation on green tea extract and its storage characteristics, this study used Streptococcus thermophilus FUA329 and S. thermophilus ST1.8748 (control group) to conduct experiments on green tea extracts. After fermentation and storage at 4 °C for 0, 30, 60, 120 and 180 d, pH, viable bacterial count, tea polyphenol content, ellagic acid content, and urolithin A content were used as the main evaluation indicators, combined with anti-oxidation activity to evaluate the storage quality of fermented green tea extract. The results showed that compared with the S. thermophilus ST1.8748 control group, the pH of S. thermophilus FUA329 fermented green tea extract during the storage period was between 5.39 and 5.71. The highest number of viable bacteria at 48 h was 9.97x108 CFU/mL. The content of tea polyphenols gradually decreased and the ellagic acid content tended to be stable. Urolithin A was produced at 48 h, and its concentration was 0.664 μmol/L. The antioxidant activity was always maintained at a high level. In summary, S. thermophilus FUA329 fermented green tea extract can significantly delay the quality decline and nutrient loss of green tea extract during storage. [ABSTRACT FROM AUTHOR]

Metabolizing ellagic acid (EA) to urolithin A with numerous bioactivities significantly improve the nutritional value of food rich in EA. In the present study, Streptococcus thermophilus FUA329 was applied to prepare pomegranate juice yogurt. The best process formula was investigated through single-factor experiments and response surface methodology. With S. thermophilus CGMCC1.8748 as control, the viability of strain, rheological properties and antioxidant activity of pomegranate juice yogurt fermented with strain FUA329 were evaluated. The content of urolithin A in pomegranate juice yogurt fermented with strain FUA329 were analyzed by high-performance liquid chromatography. The results showed that the optimal fermentation conditions for preparing pomegranate juice yogurt by S. thermophilus FUA329 were 15.79% pomegranate juice content, 7.08% sucrose content and 3.04% starter inoculum size, fermentation at 37 °C for 7 h and comprehensive sensory score was 79.4 points. Under the optimal conditions, the results of basic indicators showed that yogurt acidity was (82.5±1.3)°T, whey precipitation was 9.6%±0.97%, color difference was 68.17±2.75, bacterial activity was 2.01±0.31 (OD600). In terms of antioxidant activity, DPPH radical, ABTS+ radical and superoxide anion radical scavenging rates of fermented pomegranate juice yogurt by strain FUA329 were 82.87%±1.48%, 88.20%±2.10% and 76.92%±1.02%, respectively, which was significantly better than plain yogurt fermented by strain FUA329 and pomegranate juice yogurt fermented by S. thermophilus CGMCC1.8748. In addition, urolithin A content was 3.31 μmol/L in fermented pomegranate juice yogurt by strain FUA329 after 7 h. The results of this study would provide a theoretical basis for fermenting a functional pomegranate juice yogurt, and lay a foundation for the development and utilization of S. thermophilus FUA329. [ABSTRACT FROM AUTHOR]

Seafood is highly perishable and has a short shelf‐life. This study investigated the effect of chitosan and alginate (CH‐SA) coating combined with the cell‐free supernatant of Streptococcus thermophilus FUA329 (CFS) as a preservative on the quailty of white shrimp (Litopenaeus vannamei) refrigerated at 4° for 0, 3, 6, 9, 12, 15 days. Freshly shrimps were randomly divided into four groups: the CFS group (400 mL); the CH‐SA group (1% chitosan/1% alginate); the CFS‐CH‐SA group (1% chitosan/1% alginate with 400 mL CFS) are treatment groups, and the control group (400 mL sterile water). The CFS–CH–SA coating effectively suppressed microbial growth total viable count and chemical accumulation (pH, total volatile basic nitrogen, thiobarbituric acid reactive substance) compared with the control. Additionally, the CFS–CH–SA coating improved the texture and sensory characteristics of shrimp during storage. The coated shrimp exhibited significantly reduced water loss (p < 0.05). The combination of CH–SA coating with CFS treatment can extend the shelf life of shrimp. Practical Application: Recently, edible films have received more consideration as a promising method to enhance the shelf life of seafood. The presence of Lactic acid bacteria metabolites in edible films reduces spoilage and improves consumer health. Our findings encourage the application of edible coating incorporated with cell‐free supernatant of Streptococcus thermophilus FUA 329 to design multifubctional foods and preserve the qualities of shrimp. [ABSTRACT FROM AUTHOR]

Vip3Aa, secreted by Bacillus thuringiensis, is effective at controlling major agricultural pests such as Spodoptera frugiperda. However, to control Vip3Aa resistance evolved in the field by different lepidoptera species, an in–depth study of sequence––structure––activity relationships is necessary to design new Vip3Aa variants. In this study, the four specific loops (β4–β5 loop, β9–β10 loop, β12–β13 loop, and β14–β15 loop) in domain III were selected and four loop mutants were constructed by replacing all residues in each specific loop with alanine. We obtained soluble proteins for three of the loop mutants, excluding the β9–β10 loop. These loop mutants have been characterized by toxicity bioassays against S. frugiperda, proteolytic processing, and receptor binding. These results indicate that the β4–β5 loop and β14–β15 loop are involved in receptor binding and Vip3Aa toxicity. Based on this, we constructed numerous mutants and obtained three single mutants (Vip3Aa–S366T, Vip3Aa–S366L, and Vip3Aa–R501A) that exhibited significantly increased toxicity of 2.61–fold, 3.39–fold, and 2.51–fold, respectively. Compared to Vip3Aa, the receptor affinity of Vip3Aa–S366T and Vip3Aa–S366L was significantly enhanced. Furthermore, we also analyzed and aligned the three–dimensional structures of the mutants and Vip3Aa. In summary, these results indicate that the loops in domain III have the potential to be targeted to enhance the insecticidal toxicity of the Vip3Aa protein. [ABSTRACT FROM AUTHOR]