Abstract:Blueberry, known as the “king of berries”, is loved by consumers because of their high nutritional value. With the rapid development of blueberry processing industry, the by-products resources generated during the processing are becoming increasingly abundant. Comprehensively improving the utilization rate of by-product resources is an important way to practice the national “grain conservation and loss reduction” strategy. Application status of blueberry processing by-products in terms of efficacy component extraction, functional activity application, biomass conversion, and intelligent food packaging was summarized. Main problems restricting the overall development of the blueberry processing by-products industry were discussed, including low level of development and utilization of by-products, incomplete extraction technology for high retention of functional components, insufficient steady-state technology for processing activity of functional extracts, and a relatively single type of high value-added functional products in the market. In view of the existing problems, it was proposed that the key measures to effectively improving the utilization of blueberry by-product resources was to tackle the high steady-state technology of active ingredients in by-products, deeply explore precise nutritional benefits of active ingredients, develop diversified and personalized functional products, and construct complete processing standards and quality assurance systems. Current situation and existing problems of resource utilization of blueberry processing by-products were systematically summarized, and rational suggestions and future development trends were proposed, aiming to provide reference for the high-value utilization and high-quality development of blueberry processing by-products.

Abstract:Walnut oil is a good highly processed product of walnut resources in China. As is well known, both the volatile flavor and the biological activity presentation of walnut oil are influenced by its raw material properties, processing methods, and storage and transportation conditions. The core is the significant changes in the internal substance composition. To some extent, the volatile flavor changes of walnut oil are important dominant indicators to evaluate its biological activity. Based on objectively evaluating the main volatile flavor characteristics of walnut oil, the composition of flavor substances in walnut oil was analyzed. Aldehydes, ketones, alcohols, heterocycles, acids, and esters are the key components that give walnut oil a unique flavor. Furthermore, the main biological activities, including anti-inflammatory, antioxidant, anti-tumor, lipid-lowering, hypoglycemic, and immune regulation of walnut oil were introduced. Additionally, the effects of factors such as walnut variety and origin, harvesting period, processing technology, and storage conditions on the flavor compounds and bioactive substances composition of walnut oil were analyzed. Finally, the internal relationship between the volatile flavor of walnut oil and the changes in its biological activity was emphasized. This relationship is not only reflected in the volatile flavor components with biological activity, but also in oxidative products, which indirectly reflect the changes in the biological activity of walnut oil. This paper aimed to analyze the scientific connotation of the correlation between nutrition and flavor of walnut oil, and provide theoretical guidance for the quality control and high-value development and utilization of walnut oil.

Abstract:Walnuts are a source of high-quality vegetable oil and have a high lipid content and favorable fatty acid composition (a ratio of linolenic to linoleic acid approaching 1∶4). Walnut oil is rich in nutritional substance and has high edible and nutritional value, and plays an important role in regulating blood lipids, antioxidation, and enhancing immunity The commercial procedures for walnut oil production commercial using the traditional pressing methods of hot-pressed and cold-pressed were reviewed, and the key aroma compounds of walnut oil based on various flavor extraction methods were summarized. The current oil flavor enhancement technologies from the aspect of raw material pretreatment, leaching and enzymatic hydrolysis were reviewed in response to the bottleneck issue of weak flavor in cold-pressed walnut oil. The pathways of lipid oxidation and Maillard reaction and the mechanism of aroma enhancement at the molecular level were expounded. This study provides new ideas and new approaches for improving the flavor quality, in order to obtain the cold-pressed walnut oil with better flavor quality, and helps the development of cold-pressed walnut oil industry.

Abstract:Fusel alcohols and esters are the key compounds affecting the quality of Huangjiu. Searching for excellent fermentative yeast strains and developing a fermentation process with low fusel alcohol production and high ester production have important theoretical value and application prospects. The Saccharomyces cerevisiae jiangnan1# was used as the starting strain, a mutation strain named YAR28 was screened through UV mutagenesis and atmospheric pressure room temperature plasma mutagenesis techniques, and the mass concentration of fusel alcohols and esters in laboratory-simulated fermented Huangjiu was used as the evaluation index. YAR28 was then subjected to spore purification screening, resulting in Saccharomyces cerevisiae with superior alcohol ester ratio production, named Saccharomyces cerevisiae Y28-23. It was cultured continuously for 5 generations to verify stability, showing no significant difference in alcohol production (P>0.05) but a 21.41% reduction in fusel alcohol mass concentration [(378.16±28.76)mg/L] compared to the starting strain and a 35.57% increase in ester concentration [(152.86±19.73)mg/L]. Saccharomyces cerevisiae Y28-23 was co-fermented with 52 non-Saccharomyces yeasts with potential ester production capabilities, and based on the evaluation index of low fusel alcohol and high ester production, the Wickerhamomyces anomalus Y34 was identified as the superior non-Saccharomyces yeast. Further optimization of the co-fermentation conditions between Saccharomyces cerevisiae Y28-23 and Wickerhamomyces anomalus Y34 revealed that co-fermenting Huangjiu with a 1∶10 addition ratio at a temperature of 20℃ during the main fermentation stage yielded optimal results for the alcohol ester ratio in Huangjiu, with a fusel alcohol concentration of (281.20±5.73)mg/L and an ester concentration of (240.02±2.47)mg/L. Compared to single-strain fermentation, the fusel alcohol mass concentration in Huangjiu decreased by 25.63%, while the ester mass concentration increased by 57.13%. Finally, based on metabolomics analysis, multiple differential metabolites and metabolic pathways closely related to substrate utilization and flavor formation during Huangjiu fermentation were obtained, elucidating the metabolic regulation of Wickerhamomyces anomalus Y34 on Saccharomyces cerevisiae Y28-23 during Huangjiu co-fermentation. This research could provide technical support for using fermentation strains to control alcohol ester content in Huangjiu brewing, and it was of reference value for the development and utilization of Huangjiu fermentation strain resources and the improvement of Huangjiu quality.

Abstract:Metabolites during Baijiu fermentation process are closely related to its unique style characteristics. Characteristics and succession of metabolites for Laobaigan Baijiu during its fermentation process have not been comprehensively analyzed. The metabolites of fermented grains during the fermentation process of Laobaigan Baijiu were identified by ultra-high performance liquid chromatography-tandem mass spectrometer. The differential metabolites were screened by principal component analysis and significant difference analysis, and then the possible metabolic pathways of these differential metabolites were annotated by KEGG database. Results showed that 2157 metabolites were detected in 9 samples of fermented grains with different fermentation time, of which 172 were extremely significant different metabolites (VIP>2, P＜0.01, |log₂(FC)|>0.1). In different stages of fermentation, the expression levels of various metabolites were different. In the early stage of fermentation (0-8d), there were the most differential metabolites, with 128 extremely significant differential metabolites(P<0.01). The metabolism of amino acids, peptides and their analogs, lipids, heterocyclic compounds, carbohydrates, and carbohydrate conjugates was significantly up-regulated. In the middle stage (8-17d), there were 22 metabolites with extremely significant differences(P<0.01). The metabolism of amino acids, peptides and their analogs was significantly up-regulated (8-14d), and lipids metabolism was up-regulated first and then down-regulated, while flavonoids metabolism was down-regulated first and then up-regulated. In the later stage (17-36d), there were 33 metabolites with extremely significant differences, and the metabolism of amino acids, peptides and their analogs, and lipids was up-regulated first and then down-regulated. In addition, 104 metabolic pathways were annotated by KEGG database, and the metabolic network diagram was depicted accordingly. In different stages of fermentation, some metabolic pathways such as carbohydrate metabolism, lipid metabolism, flavonoid metabolism, and amino acid metabolism became more active mainly in the early stage of fermentation(P＜0.05), flavonoid metabolism was more active in the middle stage of fermentation(P＜0.05), lipid metabolism and amino acid metabolism were more vigorous in the late stage of fermentation(P＜0.05). Eighteen metabolites, such as serine, glutamine, and aspartate semialdehyde, showed significant differences in several fermentation stages, and they annotated galactose metabolism, glycine, serine and threonine metabolism, arginine and proline metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, and glycerophosphate metabolism, which may be the potential pathways to produce flavor compounds. Based on metabonomics technology, the characteristics and succession of metabolites during the fermentation process of Laobaigan Baijiu were revealed, which could provide a theoretical basis for analyzing the flavor metabolism mechanism during the fermentation process of Laobaigan Baijiu.

Abstract:In order to investigate the acid-enhancing effect of commercial Kluyveromyces and its effect on wine quality, Cabernet Sauvignon grapes from the eastern foot of Helan Mountain were used as raw materials. Three commercial Kluyveromyces strains were selected, two Lachancea thermotolerans strains (1 strain with trade name Excellence X-FRESH, referred to as “Excellence X”, and 1 strain with trade name ZYMAFLORE OMEGALT, referred to as “ZO”) and 1 Kluyveromyces thermotolerans strain (trade name CVE-7, referred to as “CVE-7”). They were subjected to sequential fermentation experiments with Saccharomyces cerevisiae (trade name Excellence XR, referred to as “XR”) at a 10∶1 inoculation amount.The effects of three strains of Kluyveromyces on organic acid content, basic physical and chemical indexes, aroma composition and sensory characteristics of wine were analyzed. The results showed that the Excellent X wine sample and CVE-7 wine sample had significant acid-enhancing effect, especially with an increase in the mass concentration of lactic acid. The basic physical and chemical indexes of all wines inoculated with Kluyveromyces met the requirements of GB/T 15037—2006. The purplish red tone of the Excellent X wine sample and the CVE-7 wine sample was significantly improved (P<0.05). Compared with the control group using only Saccharomyces cerevisiae, the aroma compounds in the wine samples prepared by mixed fermentation were more abundant and the mass concentration was higher, especially the total mass concentrations of ethyl lactate, higher alcohols and fatty acids were significantly increased (P<0.05). The principal component analysis of aroma active compounds with OAV greater than 1 showed that the Excellent X wine sample had richer esters, higher alcohols and fatty acids. CVE-7 wine sample increased the mass concentration of decanal, 2,3-butanedione, isoamyl caproate and other compounds. The ZO wine samples were rich in esters and had a high concentration of isoamyl alcohol.The results of subjective evaluation showed that the scores of Excellent X wine samples and CVE-7 wine samples were higher, followed by ZO wine samples, and the lowest was the control group without mixed fermentation. The results showed that the three commercial Kluyveromyces strains had positive effects on the quality of Cabernet Sauvignonwine in the eastern foot of Helan Mountain. In particular, the acid-enhancing effects of Excellence X and CVE-7 were good, and they could be used as acid-enhancing strains for low-acid Cabernet Sauvignon raw materials in the eastern foot of Helan Mountain. It was hoped that the research could provide reference for the acid-enhancing brewing technology of Cabernet Sauvignon wine and provide theoretical basis for the improvement of wine quality.

Abstract:The medium-high temperature Daqu (ZGW) and medium temperature Daqu(ZW)are mainly used for fermentation starter for strong flavor Baijiu. In the early days, ZW was used in the production of strong flavor Baijiu. At present, most of the production of strong flavor Baijiu has turned to ZGW. However, due to the lack of in-depth understanding of the differences in flavor and mechanism of strong flavor Baijiu brewed by 2 types of Daqu, choosing ZGW or ZW has become an urgent problem for the industry. In order to regulate and control the fermentation process to obtain better quality strong flavor Baijiu, the physicochemical indexes, enzyme activity indexes and microbial community structure of 2 types of Daqu were analyzed, and the influence path and function of different microorganisms on the flavor formation of strong flavor Baijiu were deeply explored. The results showed that acidity and protease activity in ZGW were significantly higher than ZW samples(P<0.05), whereas saccharification power, liquefaction power and fermentation power in ZW were significantly higher than ZGW(P<0.05), and there were no significant differences in water, starch and reducing sugar content between the 2 types of Daqu. 20 Dominant fungal species and 20 dominant bacterial species were detected in 2 types of Daqu. According to the identification of fungal species, the main dominant fungal species of ZGW were Thermoascus aurantiacus (24.64%), Dipodascus geotrichum (13.39%), Wickerhamomyces anomalus (8.04%). The main dominant fungal species of ZW were Candida tropicalis (40.00%), Kodamaea ohmeri (12.80%), Trichosporon coremiiforme (10.98%). For bacterial species, the main dominant bacterial species of ZGW were Acinetobacter johnsonii XBB1 (32.49%), Lactobacillus sakie (16.80%), Pseudomonas putida (10.68%). The main dominant bacterial species of ZW were Lactobacillus sakie (39.32%), Acinetobacter johnsonii XBB1 (18.45%), Enterococcus faecium (13.00%). Moreover, 23 differential species were found in 2 types of Daqu,including 14 species of fungi and 9 species of bacteria. According to microbial function prediction, there were abundant enzymes about carbon and nitrogen metabolism in 2 types of Daqu. The abundance of saccharify and fermentation enzymes in ZW was higher than ZGW, indicating the potential ethanol production ability of ZW was stronger than ZGW. The abundance of enzymes related to acid production and nitrogen metabolism in ZGW was higher than ZW, indicating the potential ability of acid production and nitrogen flavor compounds in ZGW was stronger than that in ZW. Through analysis of physicochemical parameters,enzyme activity, microbial community structure and metabolic function of 2 types of Daqu, the differences between 2 types of Daqu were further understood, to provide theoretical basis and technical guidance for strong flavor Baijiu production.

Abstract:i>Monascus yellow pigments are common natural food pigments with various physiological effects, but their poor water solubility and sensitivity to light, heat, and pH, which limit their wide application in food field. Water-soluble flaxseed protein (FPW) was used as a carrier to prepare the complex between FPW amd Monascus yellow pigments. The interaction hehavior between two types of Monascus yellow pigments (Monascin, MS and Ankaflavin, AK) and FPW was studied using combined spectral method. The dispersion and stability changes of pigments combined with FPW and Monascus pigments (Mps) which riched in Monascus yellow pigments in aqueous solution were investigated. Fluorescence spectroscopic analysis indicated that both MS and AK bound to FPW in the static quenching mode, and there was only one binding site. The binding constant of FPW-AK system was larger than that of FPW-MS system. The results of thermodynamic parameters demonstrated that the main forces maintaining FPW-MS system were hydrogen bond and van der Waals force, while those maintaining FPW-AK system were hydrogen bond and electrostatic attraction. Synchronous fluorescence spectrum and three-dimensional fluorescence spectrum showed that the addition of MS or AK changed the microenvironment of the amino acid residues of FPW, resulting in the conformational change of FPW. Analysis of UV-Vis and infrared spectroscopy further indicated that the secondary structure of FPW was changed after the addition of MS and AK. In addition, the combination of FPW and Mps could improve the dispersibility of Mps in water. After forming complexes with different concentrations of FPW, the retention rates of FPW-Mps were increased by 9.53%, 16.92%, and 31.37% compared to free Mps at a temperature of 25℃, a light intensity of 3900Lux, and a light duration of 72h. At temperatures of 4,25, and 50℃, and under light avoidance conditions, the retention rates of FPW-Mps increased by 25.65%, 22.04%, and 25.98% compared to free Mps. At a temperature of 25℃, pH values of 3,5, 7,9, and 11, and under light avoidance conditions, the retention rates of FPW-Mps increased by 10.27%, 12.96%, 12.06%, 17.82%, and 7.27% compared to free Mps, respectively. After composite with FPW, the retention rates of Mps increased under different illumination time, temperatures, and pH conditions, indicating that FPW could improve the photostability, thermal stability, and acid-base stability of Mps. This study aimed to provide new ideas for the stability study of Monascus yellow pigments.

Abstract:The main forms of cyanidin-3-O-glucoside (C3G) in various pH environments are different,leading to differences in its antioxidant capacity. Black bean protein,a common dietary protein, has the potential to serve as a carrier for unstable bioactive compounds. Understanding the interaction mechanism between black bean protein and C3G is beneficial for their application in food systems. Interactions between β-conglycinin(7S)and glycinin(11S)soybean proteins with C3G and their effects on the oxidative stability and antioxidant capacity of C3G at pH 2.0,5.0,and 7.0 were investigated using various spectroscopic analyses and molecular docking experiments. The results showed that binding of C3G with 7S and 11S at pH 2.0 and 5.0 not only reduced the hydrophobic environment around Tyr residues and increased polarity,but also increased α-helical content and decreased β-sheet content in both 7S and 11S. At pH 7.0,the presence of C3G led to an increase in both α-helical and β-sheet content in 7S and 11S except for β-turns. Furthermore,the binding of C3G with 7S and 11S was an exothermic process,and at different pH conditions,hydrogen bonding and van der Waals forces were the main driving forces for the interaction between C3G with 7S and 11S,resulting in static fluorescence quenching of 7S and 11S. Both 7S and 11S exhibited the highest affinity for C3G at pH 7.0. Molecular docking revealed that GLU229,ARG356,and PRO101 residues on 7S,and ARG161,VAL162,ILE171,and THR176 residues on 11S played key roles in the binding with C3G. Moreover,the binding of 7S and 11S with C3G significantly enhanced the oxidative stability and antioxidant capacity of C3G at different pH conditions.

Abstract:Mycotoxin present a significant risk to the safety of food, while pamamycin exhibits promising biological antibacterial properties against pathogenic fungi. In order to enhance the production of pamamycin, the differences in growth and metabolism, intracellular metabolites, and metabolic pathways of Streptomyces alboflavus TD-1 in two distinct fermentation media, one containing 1,2-propanediol and the other without it were studied based on metabolomics analysis method. The alterations in metabolite levels were examined in conjunction with the interplay between significantly different metabolite content changes and metabolic pathways to elucidate the underlying mechanism responsible for the high-yield biosynthesis of pamamycin. The findings of this study indicated that the addition of 1,2-propanediol increased the production of pamamycin by Streptomyces alboflavus TD-1. Through the utilization of gas chromatography-mass spectrometry, a total of 27 intracellular metabolites were identified as significantly different, and these metabolites were found to be closely associated with the biosynthesis of pamamycin. These metabolites were primarily involved in central carbon metabolism, amino acid metabolism, and fatty acid metabolism pathways. Furthermore, by employing a verification strategy of adding significant different precursors, the supplementation of glutamic acid resulted in a 102.33% increase in pamamycin yield. The supplementation of significantly different precursors, based on analysis of metabolomics, proved to be an effective approach for enhancing the yield of pamamycin. The objective of this study was to mitigate the adverse effects of Aspergillus flavus and aflatoxins contamination on grain processing foods, while also to ensure food safety from the source.

Abstract:Phthalate esters (PAEs) show physiological toxicity, and the key to reduce toxicity lies in the complete cleavage of side chain ester bonds. Amidohydrolase RhoⅡ is a hydrolytic enzyme acting on ester bond of monoalkyl phthalate esters, but cannot hydrolyze PAEs. RhoⅡ was modified by computer simulation and site-directed mutation to achieve the purpose of PAEs hydrolysis. Results of the molecular docking between RhoⅡ and monobutyl phthalate (MBP) showed that RhoⅡ stabilized the carboxyl group of MBP with R-groups of Lys200 and Arg185, and both monomers of MBP and RhoⅡ formed hydrogen bond interactions. The site-directed mutation indicated that Asp39, Lys127 and Cys160 formed the catalytic triplet of RhoⅡ, which as the active center positioned in the hydrophobic cavity of the enzymes. Additionally, the mutant enzyme F44N was obtained through site-directed mutation and could hydrolyze PAEs, which significantly improved the enzymatic hydrolysis efficiency toward dibutyl phthalate (DBP) and diisobutyl phthalate (DIBP) compared with the original enzyme. After phenylalanine mutated to asparagine, the steric hindrance effect of the enzyme on the substrate was significantly weakened, and the substrate binding cavity of the enzyme increased. DBP and DIBP could bind to the catalytic pocket of the enzyme to achieve ester bond cleavage. The catalytic mechanism was speculated based on molecular docking and mutation. The mutation might affect the substrate binding cavity, and the mutant enzyme could not effectively bind to the monoalkyl phthalate esters. This work performed sequence and structure analysis of RhoⅡ, and verified the catalyzed triplet. By finding the catalytic activity center of RhoⅡ and mutating the key site, the substrate specificity of RhoⅡ was changed. This study hoped that the enzyme resources related to enzymatic catalytic hydrolysis of PAEs could be expanded and promoted the application of related hydrolases.

Abstract:In order to find and explore new enzymes for degrading fucoidan, a strain of marine Flavobacterium sp. RC2-3 which can degrade fucoidan was screened from kelp as the research object, and its whole genome was sequenced. By comparing with the amino acid sequence of fucoidanase reported, transcriptomic analysis and real-time fluorescence quantitative PCR verification, a possible fucoidanase gene was discovered and named Fcn1. The full length of Fcn1 gene is 1221bp, encoding 406 amino acids, and the molecular weight of the protein is about 46.8kDa. By primer design and PCR amplification, the Fcn1 gene was cloned, and the heterologous expression vector Fcn1-pET-28a (+) was further constructed, and it was successfully induced and expressed in E.coli BL21(DE3) expression host.The recombinant enzyme Fcn1 was separated and purified by a nickel column with His tag. The specific enzyme activity of the purified enzyme in hydrolyzing fucoidan was 332U/mg determined by potassium ferricyanide method, and the purification multiple was 2.25. Enzymatic property study showed that the optimal reaction temperature of Fcn1 was 50℃, the optimal reaction pH was 8.0, and the stability of Fcn1 was better at 20-30℃ and pH 7.0-8.0. Combined with the results of enzymatic properties, the optimum reaction conditions were determined to be 30℃ at pH 8.0, and the kinetic parameters of enzymatic hydrolysis of fucoidanase were determined, with K_m of 1.17mg/mL, V_max of 10.53g·L-1·min-1. The enzyme has high activity in degrading fucoidan, and has great application potential in the development and utilization of fucoidan resources.

Abstract:The protective effect of D-fructose on spores of Bacillus subtilis treated by high-pressure thermal sterilization (HPTS) was studied. The treatment pressure of HPTS was 200 and 600MPa, the treatment temperatures were 25,65, and 75℃, the treatment time was 20min, and the mass fractions of D-fructose were 0,15%, 30%, 60%. At these conditions, flow cytometry was used to detect the damage of spore inner membrane before and after treatment, and Fourier infrared spectroscopy was used to analyze spore protein and inner membrane lipids before and after treatment to reveal the changes in protein structure and inner membrane lipid phase. After HPTS treatment, the permeability of spore inner membrane increased and the integrity of spore inner membrane was damaged. However, with the increase of D-fructose mass fraction, the phase state of spore inner membrane lipids gradually changed from liquid crystal state to gel state, stability of inner membrane increased, permeability decreased, integrity improved, and the content of ordered secondary structure of spore protein increased. When D-fructose was not added, after treatment at 600MPa and 75℃ for 20min, the 5.31 lg(CFU/mL) spores died,and the OD₆₀₀ of spore suspension decreased to 0.41, the leakage rate of 2,6-pyridinedicarboxylic acid (DPA) reached 93.56%, the proportion of spores with inner membrane damage reached 80.95%, and the content of α-helix and β-fold structures in spore proteins decreased to 16% and 17%, respectively. When the mass fraction of D-fructose increased to 60%, the number of viable spores increased by 1.69 lg(CFU/mL) under the same HPTS treatment conditions, the OD₆₀₀ of spore suspension increased by 0.09, the proportion of spores with inner membrane damage decreased by 20.74%, and the contents of α-helix and β-fold structures of spore proteins increased to 25% and 28%, respectively. D-fructose protected the spore structure and key substances in spores during HPTS treatment, and this protective effect was positively correlated with the mass fraction of D-fructose.

Abstract:Grass carp are perishable due to the growth of microorganisms during storage, which restricts the development of its processing industry to some extent. Microbial interactions are important factors affecting food spoilage. In order to explore the roles of microbial interactions in the deterioration of grass carp quality, Pseudomonas putida (P. putida) and Shewanella putrefaciens (S. putrefaciens) were co-inoculated into grass carp flesh and arginine solutions. The effects of the interactions between P. putida and S. putrefaciens on their growth and spoilage potentials were evaluated by detecting total viable counts, soluble peptides, free ammonia, and putrescine changes in co-inoculated fish flesh and the putrescine production in the co-inoculated arginine solutions. Results showed that P. putida had potent activity in producing siderophores and inhibited the growth of S. putrefaciens in fish flesh by competing for ferric irons. The interactions between P. putida and S. putrefaciens increased the ammonia content of fish flesh in the first 11d of storage and facilitated the putrescine production in the first 8d of storage, but had no promoting effect on the production of soluble peptides. After 11d of storage, P. putida and S. putrefaciens did not promote the production of free ammonia and putrescine through interaction effects due to the inhibition of S. putrefaciens growth. P. putida was able to enhance the putrescine-producing activity of S. putrefaciens by providing arginine-degrading products through the arginine deiminase pathway. Overall, P. putida and S. putrefaciens facilitated the quality deterioration of grass carp during storage (0-11d) through microbial interactions like metabiosis. S. putrefaciens played a primary role in grass carp spoilage and the interactions with P. putida. More attention should be paid to the control research of S. putrefaciens in the development of fish preservation techniques.