Production Of Amines Research Articles

Robust and safe: Unveiling Bacillus clausii OHRC1's potential as a versatile probiotic for enhanced food quality and safety

This research underscores the exceptional potential of Bacillus clausii as a probiotic for food products. Our study assessed Bacillus clausii under simulated gastrointestinal conditions, revealing its impressive resilience: 58% resistance to pepsin, 70% to bile salts and pancreatin, and 41% viability at low pH. It also showed significant auto-aggregation (42.87%) and co-aggregation with Escherichia coli ATCC 35150 (44.6%), Bacillus cereus ATCC 13061 (59.7%), and Staphylococcus aureus ATCC 13150 (30.9%). The strain's antibiotic sensitivity profile—susceptible to ampicillin and vancomycin, resistant to trimethoprim and erythromycin—ensures its safety for food use, confirmed by the absence of hemolysis, gelatinase activity, biogenic amine production, and toxicity in Caenorhabditis elegans. Remarkably, Bacillus clausii exhibited high thermal stability, with survival rates up to 96.31% at 90 °C for 30 min and 82.76% at 100 °C for 60 min, and a broad pH tolerance (41%–99.7% survival from pH 2 to 12). The strain's response to heat stress involved key antimicrobial and spore formation genes (spaS, sboA, BAC A, and SPO). This study establishes Bacillus clausii OHRC1 as a robust, safe, and versatile probiotic, suitable for enhancing food quality and safety in ready-to-eat products.

Zinc Supplementation Improves Texture, Oxidative Stability of Caciotta Cheese and Reduces Biogenic Amines Production.

Zinc is essential for animals, playing a vital role in enzyme systems and various biochemical reactions. It is crucial to ensure a sufficient intake of zinc through the diet to maintain efficient homeostasis. Only few studies on zinc effect in cow lactating diet evaluated the effects on milk and cheese quality, with conflicting findings. 24 cows of the Friesian breed were divided into two groups (CTR: control and TRT: treated group). Cows were selected for age, body weight, parity and phase of lactations (mid lactation, 140-160 days). CTR diet contained 38 mg/kg of Zn and TRT diet was supplied with 120 mg/kg of complete feed for 60 days. The objective of current investigation was to evaluate the impact of a dietary Zinc Oxide (ZnO) integration of lactating Friesian cows on chemical composition, zinc content, fatty acid and proteic profile, ammine content, pH, aw, texture, and sensory profile of cheese and to improve the chemical-nutritional quality of milk and cheese. The results showed that ZnO supplementation reduced mesophilic aerobic bacteria and Presumptive Pseudomonas spp. growth, proteolysis, biogenic amines content, lipid oxidation, odour intensity and sour and increased hardness, gumminess, chewiness, elasticity of cheese. Biogenic amines are considered an important aspect of food safety. ZnO integration in cow diet could represent a promising strategy for improving the quality, the safety and shelf-life of caciotta cheese.

Asymmetric hydrogenation of ketimines with minimally different alkyl groups.

Asymmetric catalysis enables the synthesis of optically active compounds, often requiring the differentiation between two substituents on prochiral substrates1. Despite decades of development of mainly noble metal catalysts, achieving differentiation between substituents with similar steric and electronic properties remains a notable challenge2,3. Here we introduce a class of Earth-abundant manganese catalysts for the asymmetric hydrogenation of dialkyl ketimines to give a range of chiral amine products. These catalysts distinguish between pairs of minimally differentiated alkyl groups bound to the ketimine, such as methyl and ethyl, and even subtler distinctions, such as ethyl and n-propyl. The degree of enantioselectivity can be adjusted by modifying the components of the chiral manganese catalyst. This reaction demonstrates a wide substrate scope and achieves a turnover number of up to 107,800. Our mechanistic studies indicate that exceptional stereoselectivity arises from the modular assembly of confined chiral catalysts and cooperative non-covalent interactions between the catalyst and the substrate.

Effect of a Chitosan-Based Packaging Material on the Domestic Storage of “Ready-to-Cook” Meat Products: Evaluation of Biogenic Amines Production, Phthalates Migration, and In Vitro Antimicrobic Activity’s Impact on Aspergillus Niger

The consumption of “ready-to-cook” foods has been experiencing rapid expansion due to modern lifestyles, and they are often sold in economical multipacks. These foods necessitate packaging that maintains their quality for extended periods of time during home storage once the original packaging is opened. This study evaluates a chitosan-based film derived from low- and high-molecular-weight (MW) chitosan in acetic acid without synthetic additives as an alternative packaging material for “ready-to-cook” beef burgers. The burgers were stored at 8 °C after being removed from their sales packaging. A commercial polyethylene (PE) film designed for food use, devoid of polyvinylchloride (PVC) and additives, served as the reference material. The production of six biogenic amines (BAs), indicative of putrefactive processes, was monitored. Additionally, the release of four phthalates (PAEs), unintentionally present in the packaging films, was assessed using solid-phase microextraction coupled with gas chromatography/mass spectrometry (SPME-GC/MS). Microbiological tests were conducted to investigate the antimicrobial efficacy of the packaging against Aspergillus Niger NRR3112. The results showed that the chitosan-based films, particularly those with low MW (LMW), exhibited superior meat preservation compared to the PE films. Furthermore, they released PAEs below legal limits and demonstrated the complete inhibition of fungal growth. These findings highlight the potential of chitosan-based packaging as a viable and effective option for extending the shelf-life and maintaining the quality of “ready-to-cook” meat products during domestic storage.

Alpibectir: Early Qualitative and Quantitative Metabolic Profiling from a First-Time-in-Human Study by Combining 19F-NMR (Nuclear Magnetic Resonance), 1H-NMR, and High-Resolution Mass Spectrometric Analyses.

Alpibectir (also known as BVL-GSK098 and GSK3729098) is a new chemical entity (NCE) with a novel mechanism for the treatment of tuberculosis. The disposition of alpibectir was determined in subjects from a first-time-in-human trial after a single oral dose of 40 mg and after 7 days repeat dosing at 30 mg. Here we present a combined approach of 19F-NMR (nuclear magnetic resonance), 1H-NMR, and high-resolution mass spectrometry (HRMS) to confidently determine the human metabolic fate of alpibectir. Utilizing multiple sites of fluorination in the molecule, it was possible to fractionate human urine and plasma to confidently detect and quantify the metabolite responses using 19F-NMR. Qualitative detection and structural characterization of F-containing NMR fractions were performed using complementary high-resolution ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) analyses to further add confidence to the metabolite responses in these fractions. Subsequent 1H-NMR then provided unequivocal standard-free structural confirmation for key metabolites, which would not be possible with conventional radioactivity detection and LC-MS/MS techniques. Alpibectir was shown to undergo extensive hydrolysis of the central amide moiety, where the resultant N-dealkylated amine and trifluorobutyric acid products were detected initially by unbiased 19F-NMR detection along with major downstream biotransformations to form a carbamoyl glucuronide conjugate and trifluoroacetic acid, respectively. Parallel UHPLC-MS/MS analyses provided confirmatory or additional structural characterization only where relevant. These concerted data allowed for the qualitative metabolic profile and quantitative determination of drug-related material (DRM) in urine and plasma, along with the percentage of dose excreted in urine, to be reported in a comprehensive, efficient, and data-led manner. SIGNIFICANCE STATEMENT: Combining the selectivity of 19F-NMR (nuclear magnetic resonance) for unfractionated samples as first-intent, data-led sample fractionation prior to 19F-NMR and structure-rich 1H-NMR detection, along with the sensitivity of high-resolution ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS), a novel alternative for time-efficient detection and quantification of drug-related material (DRM) in human without use of radiolabeled drug is reported. This allowed more complete data rationalization of human metabolism, permitting early risk assessment and progression of the development of antitubercular agent, alpibectir.

Tailoring the d‐band centers enables NiM alloy to be multifunctional site for tandem reductive amination

AbstractIntegrating multi‐step reactions through tandem catalysis offers potential for efficient chemical engineering processes, but designing an efficient tandem catalyst is challenging. Herein, we report tailoring the d‐band centers of Ni through alloying with a second metal (M = Fe/Co/Cu/Ga), which enables it to be multifunctional site for tandem reductive amination. A linear correlation of d‐band center with yield of primary amine product was observed. Density functional theory and experiments revealed the upshifted d‐band center strengthened the adsorption of Schiff base intermediate in advantageous di(C&N) mode, also narrowed the adsorption energy gap between NH3 and H2. Furthermore, the multifunctional nanoparticles provide a confined space with short diffusion pathway for NH3* and H* to timely react with Schiff base. As a result, the NiFe/AlOx with a d‐band center nearest to the Fermi level exhibited the highest primary amine yield of 96.2% with five consecutive reusability under extremely low H2 pressure, which is superior to other reported precious‐metal‐based catalysts.

Screening and evaluation of a novel nucleotide-degrading Levilactobacillus brevis grx821 with anti-hyperuricemia ability

Hyperuricemia seriously impacts our health and life quality. Probiotics play a vital role in ameliorating hyperuricemia through decrease urate production by purine substance assimilation. However, most research screened probiotics based on the assimilation of purine nucleoside, ignoring nucleotides. Nucleosides are derived from nucleotides. We hypothesized that lactic acid bacteria with the ability of nucleotides assimilation might be better to reduce intestinal absorption of dietary purine substances. In this study, a total of 235 strains of lactic acid bacteria were isolated from Chinese traditional fermented foods and evaluated for their purine nucleotides assimilation ability. A new potential candidate Levilactobacillus (L.) brevis grx821 isolated from naturally fermented soy whey Suanjiangshui, with a strong ability to degrade purine nucleotides and purine nucleosides, effectively reduced the serum levels of UA and creatinine in hyperuricemia mice by 20.76% and 14.38%. Based on the evaluation of antibiotic susceptibility, production of nitrite and biogenic amines, and hemolytic activity, L. brevis grx821 can be considered safe. L. brevis grx821 showed good gastrointestinal tolerance in vitro and cow milk fermentation characteristics, and could be a promising candidate of dietary supplements for prevention of hyperuricemia. This study suggests a novel way screening potential probiotic candidate for hyperuricemia, which has great guiding significance in the dealing with hyperuricemia.

Mechanism of Z-Selective Allylic Functionalization via Thianthrenium Salts.

A detailed mechanistic study of the Z-selective allylic functionalization via thianthrenium salts is presented. Kinetic analyses, deuterium labeling experiments, and computational methods are used to rationalize the observed reactivity and selectivity. We find that the reaction proceeds via a rate-determining and stereodetermining allylic deprotonation of an alkenylthianthrenium species. The Z-configuration of the resultant allylic ylide is translated into the Z-allylic amine product through a sequence of subsequent fast and irreversible steps: protonation to form a Z-allylic thianthrenium electrophile and then regioselective substitution by the nucleophile. In the stereodetermining deprotonation step, computational studies identified a series of stabilizing nonbonding interactions in the Z-alkene-forming transition state that contribute to the stereoselectivity.

Continuous Homogeneously Catalyzed Production of Fatty Amines in Microemulsions─Proof of Concept in a Mini-Plant

Continuous Homogeneously Catalyzed Production of Fatty Amines in Microemulsions─Proof of Concept in a Mini-Plant

Effects of pickle brine and glycine addition on biogenic amine production in pickle fermentation

This study investigated the effects of different pickle brines and glycine additions on biogenic amine formation in pickle fermentation. The results showed that the brines with higher biogenic amine content led to the production of more biogenic amines in the simulated pickle fermentation system. This was related to the abundance of biogenic amine-producing microorganisms in the microbial communities of the brines. Metagenome analysis of the brines and metatranscriptome analysis of the fermentation systems showed that putrescine was primarily from Lactobacillus, Oenococcus, and Pichia, while histamine and tyramine were primarily from Lactobacillus and Tetragenococcus. Addition of glycine significantly reduced the accumulation of biogenic amines in the simulated pickle fermentation system by as much as 70 %. The addition of glycine had no inhibitory effect on the amine-producing microorganisms, but it down-regulated the transcription levels of the genes for enzymes related to putrescine synthesis in Pichia, Lactobacillus, and Oenococcus, as well as the histidine decarboxylase genes in Lactobacillus and Tetragenococcus. Catalytic reaction assay using crude solutions of amino acid decarboxylase extracted from Lactobacillus brevis showed that the addition of glycine inhibited 45 %–55 % of ornithine decarboxylase and tyrosine decarboxylase activities. This study may provide a reference for the study and control of the mechanism of biogenic amine formation in pickle fermentation.

Antimicrobial Activity, Genetic Relatedness, and Safety Assessment of Potential Probiotic Lactic Acid Bacteria Isolated from a Rearing Tank of Rotifers (Brachionus plicatilis) Used as Live Feed in Fish Larviculture.

Aquaculture is a rapidly expanding agri-food industry that faces substantial economic losses due to infectious disease outbreaks, such as bacterial infections. These outbreaks cause disruptions and high mortalities at various stages of the rearing process, especially in the larval stages. Probiotic bacteria are emerging as promising and sustainable alternative or complementary strategies to vaccination and the use of antibiotics in aquaculture. In this study, potential probiotic candidates for larviculture were isolated from a rotifer-rearing tank used as the first live feed for turbot larvae. Two Lacticaseibacillus paracasei and two Lactiplantibacillus plantarum isolates were selected for further characterization due to their wide and strong antimicrobial activity against several ichthyopathogens, both Gram-positive and Gram-negative. An extensive in vitro safety assessment of these four isolates revealed the absence of harmful traits, such as acquired antimicrobial resistance and other virulence factors (i.e., hemolytic and gelatinase activities, bile salt deconjugation, and mucin degradation, as well as PCR detection of biogenic amine production). Moreover, Enterobacterial Repetitive Intergenic Consensus-PCR (ERIC-PCR) analyses unveiled their genetic relatedness, revealing two divergent clusters within each species. To our knowledge, this work reports for the first time the isolation and characterization of Lactic Acid Bacteria (LAB) with potential use as probiotics in aquaculture from rotifer-rearing tanks, which have the potential to optimize turbot larviculture and to introduce novel microbial management approaches for a sustainable aquaculture.

Exploring the core microorganisms and mechanisms responsible for biogenic amines production during soy sauce fermentation

Hazardous levels of biogenic amines (BA) are frequently detected in soy sauce. However, the microorganisms and mechanisms responsible for BA formation in soy sauce are not well understood. In this study, we investigated the dynamic changes and metabolic pathways of BAs during soy sauce fermentation via metabolome and metagenomic analyses. Spermidine and putrescine were the main BAs detected during koji making, while putrescine, tyramine, phenylethylamine, and histamine were dominant during moromi fermentation. PCA analysis revealed that the soy sauce fermentation process could be divided into five representative stages based on the dynamics of BAs. Metagenomic analysis uncovered that a total of 15 genera were mainly involved in BAs formation, particularly, histamine was principally produced by Klebsiella, and Bacillus was the major tyramine-synthesizing bacteria. Correlation analysis showed that pH increase inhibited the spermidine production during koji making, whereas elevated NaCl concentration facilitated the phenylethylamine formation during moromi fermentation. Co-occurrence network analysis unveiled the associations between the BA-producing microorganisms and other genera. Overall, these results have improved our understanding of the mechanism of BA formation during soy sauce fermentation and guided the development of fermentation agents capable of degrading BA in industrial manufacture soy sauce production.

Physiological properties evaluation and exopolysaccharide biosynthesis of Limosilactobacillus fermentum JL-2 from Chinese traditional fermented dairy product based on genomic insight

Limosilactobacillus fermentum JL-2 with high production of exopolysaccharide (EPS) was screened from the traditional fermented dairy product in Xinjiang district (China) in our previous work. In this study, the whole genome of L. fermentum JL-2 was sequenced and the genomic information and function were studied to excavate its genotype, safety and probiotic properties. The safety evaluation in vitro showed that L. fermentum JL-2 was not hemolytic, sensitive to common antibiotics, and it had a weak biogenic amine production capacity. The genes related to EPS biosynthesis and their relationship with EPS production were discussed. The EPS production of L. fermentum JL-2 was 553.6 mg/L. The genome of L. fermentum JL-2 consisted of a circular 1.98 Mbp chromosome. A variety of genes related to probiotic properties such as acid tolerance, bile salt tolerance, adhesion to gut mucosa and environmental stress resistance were contained. A complete EPS gene cluster was found in the genome of L. fermentum JL-2, and the genes related to EPS biosynthesis such as epsA and epsB were found in L. fermentum JL-2. It is worth noting that EPS biosynthesis protein (gene0099) seemed to play a key role in the EPS synthesis of L. fermentum JL-2. These results revealed the potential of L. fermentum JL-2 as a probiotic at the gene level. Therefore, this study laid a theoretical foundation for further research into its potential probiotic function and its application in practice.

Highly Efficient Thiolate-Based Ionic Liquid Catalysts for Reduction of CO2: Selective N-Functionalization of Amines to Form N-Formamides and N-Methylamines.

Developing efficient catalysts to convert CO2 into value-added chemicals is valuable for reducing carbon emissions. Herein, a kind of novel thiolate-based ionic liquid with sulfur as the active site was designed and synthesized, which served as highly efficient catalyst for the reductive N-functionalization of CO2 by amines and hydrosilane. By adjusting the CO2 pressure, various N-formamides and N-methylamines were selectively obtained in high yields. Remarkably, at the catalyst loading of 0.1 mol %, the N-formylation reaction of N-methylaniline exhibited an impressive turnover frequency (TOF) up to 600 h-1, which could be attributed to the roles of the ionic liquids in activating hydrosilane and amine. In addition, control experiments and NMR monitoring experiments provided evidence that the reduction of CO2 by hydrosilane yielded formoxysilane intermediates that subsequently reacted with amines to form N-formylated products. Alternatively, the formoxysilane intermediates could further react with hydrosilane and amine to produce 4-electron-reduced aminal products. These aminal products served as crucial intermediates in the N-methylation reactions.

Mechanochemical Synthesis of Chromium(III) Complexes Containing Bidentate PN and Tridentate P-NH-P and P-NH-P' Ligands.

Chromium(III) complexes bearing bidentate {NH2(CH2)2PPh2: PN, (S,S)-[NH2(CHPh)2PPh2]: P'N} and tridentate [Ph2P(CH2)2N(H)(CH2)2PPh2: P-NH-P, (S,S)-(iPr)2PCH2CH2N(H)CH(Ph)CH(Ph)PPh2: P-NH-P'] ligands have been synthesized using a mechanochemical approach. The complexes {cis-[Cr(PN)Cl2]Cl (1), cis-[Cr(P'N)Cl2]Cl (2), mer-Cr(P-NH-P)Cl3 (3), and mer-Cr(P-NH-P')Cl3 (4)} were obtained in high yield (95-97%) via the grinding of the respective ligands andthe solid Cr(III) ion precursor [CrCl3(THF)3] with the aid of a pestle and mortar, followed by recrystallization in acetonitrile. The isolated complexes are high spin. A single-crystal X-ray diffraction study of 2 revealed a cationic chromium complex with two P'N ligands in a cis configuration with P' trans to P' with chloride as the counteranion. The X-ray study of 4 shows a neutral Cr(III) complex with the P-NH-P' ligand in a mer configuration. The difference in molecular structures and bulkiness of the ligands influence the electronic, magnetic, and electrochemical properties of the complexes as exhibited by the bathochromic shifts in the electronic absorption peaks of the complexes and the relative increase in the magnetic moment of 3 (4.19 μβ) and 4 (4.15 μβ) above the spin only value (3.88 μβ) for a d3 electronic configuration. Complexes 1-4 were found to be inactive in the hydrogenation of an aldimine [(E)-1-(4-fluorophenyl)-N-phenylmethanimine] under a variety of activating conditions. The addition of magnesium and trimethylsilyl chloride in THF did cause hydrogenation at room temperature, but this occurred even in the absence of the chromium complex. The hydrogen in the amine product came from the THF solvent in this novel reaction, as determined by deuterium incorporation into the product when deuterated THF was used.

Cereus jamacaru DC. (mandacaru) fruit as a source of lactic acid bacteria with in vitro probiotic-related characteristics and its protective effects on Pediococcus pentosaceus during lyophilization and refrigeration storage

This study isolated and identified autochthonous lactic acid bacteria (LAB) from mandacaru fruit and evaluated their potential probiotic and technological aptitudes in vitro, as well as the protective effects of freeze-dried mandacaru fruit on the most promising LAB isolate during lyophilization and refrigeration storage. Initially, 212 colonies were isolated from mandacaru fruit, and 34 were preliminarily identified as LAB. Thirteen isolates identified by 16S-rRNA sequencing as Pediococcus pentosaceus were negative for DNase, gelatinase, hemolytic, and biogenic amine production. The selected isolates showed proteolytic activity, diacetyl and exopolysaccharide production, and good tolerance to different NaCl concentrations while having low cellular hydrophobicity and antagonistic activity against pathogens. The survival of isolates sharply decreased after 3 h of exposure to pH 2 and had a good tolerance to 1 % bile salt. A principal component analysis selected P. pentosaceus 57 as the most promising isolate based on the examined technological and probiotic-related physiological properties. This isolate was lyophilized with mandacaru fruit and stored under refrigeration for 90 days. P. pentosaceus 57 lyophilized with mandacaru fruit had high viable cell counts (9.69 ± 0.03 log CFU/mL) and >50 % of physiologically active cells at 90 days of refrigeration storage. The results indicate that mandacaru fruit is a source of P. pentosaceus with aptitudes to be explored as potential probiotic and technological characteristics of interest for the food industry, besides being a good candidate for use in lyophilization processes and refrigeration storage of LAB due to its cryoprotective effects.

Facile Cu–MOF-derived Co3O4 mesoporous-structure as a cooperative catalyst for the reduction nitroarenes and dyes

The present study describes the environmentally friendly and cost-effective synthesis of magnetic, mesoporous structure-Co3O4 nanoparticles (m-Co3O4) utilizing almond peel as a biotemplate. This straightforward method yields a material with high surface area, as confirmed by various characterization techniques. Subsequently, the utilization of m-Co3O4, graphene oxide (GO), Cu(II)acetate (Cu), and asparagine enabled the successful synthesis of a novel magnetic MOF, namely GO–Cu–ASP–m-Co3O4 MOF. This catalyst revealed remarkable stability that could be easily recovered using a magnet for consecutive use without any significant decline in activity for eight cycles in nitro compound reduction and organic dye degradation reactions. Consequently, GO–Cu–ASP-m-Co3O4 MOF holds immense potential as a catalyst for reduction reactions, particularly in the production of valuable amines with high industrial value, as well as for the elimination of toxic-water pollutants such as organic dyes.

An efficient and stable LDH-derived Ni catalyst for highly selective hydrogenation of nitriles to primary amines

Transformation of nitriles into amines is highly desired, yet stable non-noble metal heterogeneous catalysts for efficiently selective production of primary amine are still lacking.Herein, for the first time we reported a Zr-doped yolk-shell structured Ni-based catalyst derived from layered double hydroxides (LDH) in the selective hydrogenation of nitriles to primary amines. The prepared catalyst exhibited higher primary amine yield (benzylamine yield >99.9 %) and significantly higher stability (>200 h) than highly efficient Ni catalysts that are reported previously in the selective hydrogenation of benzonitrile. Other nitriles are transformed into primary amines with good yields (90–100 %). The strong interaction between Ni0yolk and shell investsNiAl catalysts with robust stability. Importantly, Zr promotes the migration of Ni2+in the shell, resulting in appropriate acidity and better hydrogen activation capability, which drives the reaction aggressively to the BA formation pathway, and thussuccessfully enhances the yield of primary amine above 99.9 %.

Semisynthesis and characterization of versatile azide intermediates using sodium alginate and its homopolymeric derivatives as starting material

Alginate, a polyuronic biopolymer composed of mannuronic and guluronic acid units, contain hydroxyl and carboxyl groups as targeting modification sites to obtain structures with new and/or improved biological properties. The copper-catalyzed azide-alkyne cycloaddition (CuAAC) is a versatile click reaction for polymer functionalization, but it typically requires a “pre-click” modification to introduce azide or alkyne groups. Here, we described a straightforward chemical path to selectively modify alginate carboxyl groups producing versatile azido derivatives through N-acylation using 3-azydopropylamine. The resulting azide-functionalized polysaccharides underwent click chemistry to yield amino derivatives, confirmed by NMR and FTIR analyses. The 1H NMR spectrum reveals a characteristic triazole group signal at 8.15 ppm. The absence of the azide FTIR band for all amino derivatives, previously observed for the N-acylation products, indicated reaction success. Antibacterial and antioxidant assessments revealed that the initial polysaccharide lacks E. coli inhibition, while the click chemistry-derived amine products exhibit growth inhibition at 5.0 mg/mL. Lower molecular weight derivatives demonstrate superior DPPH scavenging ability, particularly amino-derivatives (24–33 % at 1.2 mg/mL). This innovative chemical pathway offers a promising strategy for developing polysaccharide structures with enhanced properties, demonstrating potential applications in various fields.

Acid tolerance response of Salmonella during the squid storage and its amine production capacity analysis.

Salmonella exhibits a strong inducible acid tolerance response (ATR) under weak acid conditions, and can also induce high-risk strains that are highly toxic, acid resistant, and osmotic pressure resistant to aquatic products. However, the induction mechanism is not yet clear. Therefore, this study aims to simulate the slightly acidic, low-temperature, and high-protein environment during squid processing and storage. Through λRed gene knockout, exploring the effects of low-acid induction, long-term low-temperature storage, and two-component regulation on Salmonella ATR. In this study, we found the two-component system, PhoP/PhoQ and PmrA/PmrB in Salmonella regulates the amino acid metabolism system and improves bacterial acid tolerance by controlling arginine and lysine. Compared with the two indicators of total biogenic amine and diamine content, biogenic amine index and quality index were more suitable for evaluating the quality of aquatic products. The result showed that low-temperature treatment could inhibit Salmonella-induced ATR, which further explained the ATR mechanism from the amino acid metabolism.