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In order to explore the key components affecting the fish sauce antioxidant activity and study the antioxidant activity and physicochemical components (soluble peptides, free amino acids and organic acids) of fish sauce at different fermentation times, correlation analysis was carried out and PLSR model was constructed. The results show that fish sauce fermented for 6 months has the highest DPPH free radical scavenging activity, reducing power, and total phenol content, which is 85.4%, 0.499, and 38.4 JLg GAE/mL respectively. After 12 months of fermentation, fish sauce has the most abundant physical and chemical substances, which are rich in TCA soluble peptides (5.81 g/100 mL), free amino acids, lactic acid (9.87 mg/100 mL), citric acid (0.56 mg/100 mL), and succinic acid (9.20 mg/100 mL). It can be known from the PLSR model, cysteine, tyrosine, praline and citric acid are the key components that affect the antioxidant activity of fish sauce. Cysteine, tyrosine and proline have a positive effect on the antioxidant activity, while citric acid has the opposite effect. This study provides a strong basis for the application of mathematical model in the analysis of antioxidant activity of fish sauce. [ABSTRACT FROM AUTHOR]

BACKGROUND Antioxidant activity has been found in fermented fish sauce. In this experiment, the properties of endogenous protease and antioxidant activity were studied in anchovy sauce during fermentation. The correlation between protease activity and antioxidant activity in fermented anchovy sauce was analyzed using the partial least squares (PLS) method. RESULTS: The results showed that at least four proteases were present in the endogenous enzyme solution, and the optimum pH values were 2.5, 5.5, 9.0, and 12.5, respectively. The maximum inhibition rate of endogenous protease, from high to low, was: serine protease inhibitor > trypsin inhibitor > aspartic protease inhibitor (pepsin inhibitor) > cysteine protease inhibitor > metalloprotease inhibitor. At the sixth month of fermentation, fish sauce had stronger trypsin, pepsin‐like activity, and antioxidant activity. At the ninth month of fermentation, the cathepsin activity was greater. A model correlating changes in protease activity with antioxidant activity suggested that the trypsin and serine protease were the main factors affecting antioxidant activity. CONCLUSION: This study reports a model correlating changes in protease activity with the antioxidant activity of fish sauce. It lays a foundation for further exploration of the formation of antioxidant substances and antioxidant effects during the process of fish sauce fermentation. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Fish sauce has a subtle flavor with prominent umami and salty taste, and is accompanied by a certain sweetness and bitterness. In order to identify a wider range of umami peptides, Chinese southern and northern anchovy sauce were selected for the study. RESULTS: Seventeen peptides were obtained by separation and purification, and their taste activity was predicted. Through the taste characterization and descriptive analysis, it was found that the synthesized peptides were umami and umami‐enhancing peptides. Seventeen umami peptides were simulated and embedded into the umami receptor T1R1/T1R3 by inserting into the Venus flytrap domain (VFTD) of the T1R3 subunit; the interaction forces were mainly hydrogen bonding, electrostatic interaction, van der Waals force and hydrophobic interaction. According to the docking interaction energies, long‐chain peptides may be easier to bind to the receptor than short‐chain peptides. Asp196, Glu128 and Glu197 were the main binding sites for docking, and could affect umami synergism. CONCLUSION: For the first time, novel umami peptides in Chinese anchovy sauce have been reported. This study is helpful for discovering umami marine resource peptides, and can provide a basis for further understanding the flavor system of anchovy sauce. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The solid-phase Maillard reaction of Alaska pollock frame (APF) mud with glucose preparation for seasoning powder was investigated. The response surface methodology was used to optimize the production conditions of APF seasoning powder according to the electronic nose and sensory evaluation. The factors affecting the sensory evaluation of the Maillard reaction were glucose addition amount>reaction temperature>reaction time>initial pH value. The optimum process parameters for the APF seasoning powder were as follows: glucose addition 9.79%, temperature 103.25°C, time 70 min, and initial pH value 7.21. The 77 volatile compounds were identified by headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) analysis. The flavor of APF seasoning powder obtained by the Maillard reaction was better than that of the raw APF powder. The aroma characteristics of different samples were detected by electronic nose, and the results were in good agreement with those of GC-MS analysis. The results of the present study demonstrated that the solid-phase Maillard reaction might be a promising method to enhance the volatile flavor of APF powder. [ABSTRACT FROM AUTHOR]

Abstract: A highly stable β-glucosidase from the viscera of China white jade snail was purified to apparent homogeneity. This purified glucosidase consisted of two identical subunits with a native molecular mass of approximately 230kDa. The maximal activity to p-nitrophenyl-β-d-glucopyranoside (pNPG) occurred at 70°C and pH 5.6. Its most notable characteristic was stable over a wide pH range (3–11 at 30°C for 24h) and a relatively high temperature (60°C for 24h). The K m for pNPG was 0.338mM and the V max was 0.25mmol nitrophenol/min/mg glucosidase at pH 5.6 and 50°C. Compared to its activity against pNPG (100%), the β-glucosidase exhibited low levels of activity against other aryl-glycosides (less than 1%). Additionally, the enzyme hydrolyzed the 20-C, β-(1→6)-glucoside of ginsenoside Rb1 to produce ginsenoside Rd, but did not hydrolyze the other β-d-glucosidic bonds of Rb1. The properties of the enzyme could make it become a useful tool in biotransformation of glucosides. [Copyright &y& Elsevier]

A scheme for industrial preparative chromatography purification of 10-deacetylpaclitaxel (10-DAP), the semi-synthesized precursor of anticancer drug paclitaxel was developed. 7-Xylosyl-10-deacetylpaclitaxel (10-DAXP) is the most abundant constitute in the needles of Taxus Chinensis, a specific yew species distributed in China. 10-DAXP has been recognized as a good material to convert into 10-DAP, the most ideal precursor of paclitaxel. The partially purified extract from yew needles which mainly contains 10-DAXP (> 60%) and other two minor 7-xylosyl-10-deacetyltaxanes including 7-xylosyl-10-deacetylcephalomannine (10-DAXC) and 7-xylosyl-10-deacetylpaclitaxel C (10-DAXP C), was used as the starting material. The total scheme can be divided into four steps. Firstly, the starting material was hydrolyzed by beta-xylosidase to remove the C-7 xylosyl group completely; and then the hydrolyzed products mainly containing 10-DAP were eluted on a column packed with resin to get crude 10-DAP (with the purity of 20.5%) with high yield (96.3%). The crude 10-DAP was purified by a column packed with normal phase, and then by a reversed-phase preparative chromatography with ODS as the solid phase. After these two steps, the purity of the aim product 10-DAP was 96% with the overall yield of 79.7%. This novel scheme was suitable for large-scale purification of 10-DAP from 10-DAXP.

The acceptor specificity and transfer potential of a beta-D-glycosidase (G I), which had been purified from the China white jade snail, were further investigated by using various sugars as acceptors. G I had broad monosaccharide acceptor specificity for its transglycosylation activity. More specifically, it efficiently catalyzed the transfer of the beta-D-fucosyl, beta-D-glucosyl or beta-D-galactosyl moiety from the corresponding p-nitrophenyl-beta-D-glycopyranosides to various monosaccharides. The transfucosylation efficiency of G I was studied by using p-nitrophenyl-beta-D-fucopyranoside (pNPFuc) as the donor and glucose and xylose as the acceptors. The yields under conditions of non-initial velocity were 88% for glucose and 93% for xylose. The transfer product with glucose as the acceptor was isolated and identified as beta-fucosyl-1,6-glucose by an NMR analysis. The data from these analyses indicate that G I had broad acceptor specificity and high efficiency for transglycosylation. These uncommon properties of G I could make it a valuable biocatalyst for the synthesis of various disaccharides.

A beta-D-xylosidase from Leifsonia shinshuensis DICP 16 was purified to apparent homogeneity using a combination of ammonium sulfate precipitation, DE 52 anion-exchange, Q-Sepharose Fast Flow anion-exchange, Toyopearl Butyl 650C hydrophobic-interaction and Sephacryl S-300 HR gel-permeation chromatography. The purified xylosidase consisted of two same subunits and had the relative molecular weight of 180 kD as determined by SDS-PAGE and gel-permeation chromatography. The maximal beta-D-xylosidase activity occurred at 55 degrees C and pH 7.0. It was stable at 45 degrees C and retained its original activity for 60 min. The stability declined rapidly when the temperature rose above 55 degrees C. The xylosidase was stable in the pH range from 6.0 to 11.0 for 20 h. At pH 7.0 and 45 degrees C the Km for p-nitrophenyl-beta-D-xylopyranoside (pNPX) was 1.04 mmol/L and the Vmx was 0.095 mmol nitrophenol/min/mg xylosidase. The enzyme was inhibited strongly by Fe2+ and Cu2+. It exhibited low levels of activity against other artificial substrates, compared to its activity against pNPX. When different natural xylosides were used as the substrates, the xylosidase showed distinct hydrolysis ability. It could hydrolyze 20-C, beta-(1-->6)-xyloside of ginsenoside Rb3 (G-Rb3) into ginsenoside Rd, but did not hydrolyze the other beta-D-glucosidic bonds of G-Rb3. Additionally, the xylosidase could not hydrolyze C-7 xylosyl-bearing taxanes.