Fluxes in CO2 and CH4 and influencing factors at the sediment-water interface in a eutrophic saline lake.

Although saline aquatic ecosystems are significant emitters of greenhouse gases (GHGs), dynamic changes in GHGs at the sediment-water interface remain unclear. The present investigation carried out a total of four sampling campaigns in Daihai Lake, which is a eutrophic saline lake situated in a semi-arid area of northern China. The aim of this study was to investigate the spatio-temporal dynamics of carbon dioxide (CO2) and methane (CH4) fluxes at the sediment-water interface and the influencing factors. The mean concentrations of porewater CO2 and CH4 were 44.98 ± 117.99 µmol L-1 and 124.36 ± 97.00 µmol L-1, far exceeding those in water column of 11.14 ± 2.16 µmol L-1 and 0.33 ± 0.23 µmol L-1, respectively. The CO2 and CH4 fluxes at the sediment-water interface (FS-WCO2 and FS-WCH4) exhibited significant spatial and temporal variations, with mean values of 9.24 ± 13.84 µmol m-2 d-1 and 3.53 ± 4.36 µmol m-2 d-1, respectively, indicating that sediment is the source of CO2 and CH4 in the water column. However, CO2 and CH4 fluxes were much lower than those measured at the water-air interface in a companion study (17.54 ± 14.54 mmol m-2d-1 and 0.50 ± 0.50 mmol m-2d-1, respectively), indicating that the diffusive flux of gases at the sediment-water interface was not the primary source of CO2 and CH4 emissions to the atmosphere. Regression and correlation analyses revealed that salinity (Sal) and nutrients were the most influential factors on porewater gas concentrations, and that gas fluxes increased with increasing gas concentrations and porosity. The microbial activity of sediment is greatly affected by nutrients and Sal. Additionally, Sal has the ability to regulate biogeochemical processes, thereby regulating GHG emissions. The present investigation addresses the research gap concerning GHG emissions from sediments of eutrophic saline lakes. The study suggests that controlling the eutrophication and salinization of lakes could be a viable strategy for reducing carbon emissions from lakes. However, further investigations are required to establish more conclusive results.

Growth and survival of common spoilage and pathogenic bacteria in ground beef and plant-based meat analogues.

To better understand the microbial quality and safety of plant-based meat analogues, this study investigated the changes of native microflora present in soy- and pea-based meat analogues (SBM and PBM) and compared them with ground beef (GB). SBM, PBM, and GB were also artificially inoculated with meat spoilage microorganisms, Pseudomonas fluorescens and Brochothrix thermosphacta, and pathogenic microorganisms, Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes; the fitness of these bacteria was evaluated during storage at refrigerated and/or abused temperatures. Results showed that the initial total aerobic plate count (APC), coliform, lactic acid bacteria (LAB), and mold/yeast (M/Y) counts for GB could be as high as 5.44, 2.90, 4.61, and 3.45 log CFU/g, while the highest initial APC, coliform, LAB, and M/Y counts found in SBM were 3.10, 2.00, 2.04, and 1.95 log CFU/g, and were 3.82, 2.51, 3.61, and 1.44 log CFU/g for PBM. The batch-to-batch differences in microbial counts were more significant in GB than in SBM and PBM. Despite the different initial concentrations, there was no difference among APC and LAB counts between the three meat types by the end of the 10-day 4 °C storage period, all approaching ca. 7.00 log CFU/g. Artificially-inoculated B. thermosphacta increased by 0.76, 1.58, and 0.96 log CFU/g in GB, PBM, and SBM respectively by the end of the refrigeration storage; P. fluorescens increased by 4.92, 3.00, and 0.40 log CFU/g in GB, PBM, and SBM respectively. Under refrigerated storage conditions, pathogenic bacteria did not change in GB and SBM. L. monocytogenes increased by 0.74 log in PBM during the 7-day storage at 4 °C. All three pathogens grew at abused storage temperatures, regardless of the meat type. Results indicated that plant-based meat could support the survival and even growth of spoilage and pathogenic microorganisms. Preventive controls are needed for ensuring the microbial quality and safety of plant-based meat analogues.

Amino acid degradation and related quality changes caused by common spoilage bacteria in chill-stored grass carp (Ctenopharyngodon idella).

To characterize the involvement of microorganisms in amino acid degradation and fish quality deterioration, three major grass carp spoilage bacteria were artificially inoculated in amino acid solutions (in-vitro) and grass carp flesh (in-situ). Results showed that Pseudomonas putida largely degraded free amino acids and produced 3.78 mM/100 g ammonia in grass carp flesh, relying on its high amino acid deamination1 activity. Aeromonas rivipollensis produced 3-Methyl-butanol and 2-Methyl-butanol through leucine and isoleucine degradation. Shewanella putrefaciens had potent ornithine-decarboxylation activity (423.91 × 10-9 µg/CFU) and released 22.98 mg/kg putrescine in situ. S. putrefaciens could produce more putrescine when cooperating with P. putida through the arginine deiminase pathway. To conclude, the biochemical activities identified through in-vitro tests correlated well with quality changes in inoculated grass carp flesh. The outcomes of this study provided fundamental information on the spoilage mechanisms of freshwater fish and important guidance for the development of quality control strategies.

Mechanisms of fish protein degradation caused by grass carp spoilage bacteria: A bottom-up exploration from the molecular level, muscle microstructure level, to related quality changes.

To demonstrate the roles of bacteria in fish protein degradation and related quality changes, three major grass carp spoilage bacteria were individually inoculated into grass carp flesh, and their effects on protein molecules, muscle structures, and quality indices were evaluated through peptidomics, optical microscopy and transmission electron microscope, and texture and water distribution analyses, respectively. Results showed that Pseudomonas putida degraded obscurin, nebulin, and titin, caused disarrangement of myofilaments and fragmented myofibers, and induced great loss of free water in muscle. Shewanella putrefaciens was active in hydrolyzing collagen and degraded both thick and thin filament proteins. Mutual separation of myofibers and severe texture softening were also observed in S. putrefaciens-inoculated samples. Aeromonas rivipollensis degraded myosin heavy chain and some thin filament proteins but less affected muscle microstructure and quality indices. Therefore, this study revealed the mechanisms of bacteria-induced grass carp protein degradation and provided guidance for developing quality control strategies.

Enhanced Thermoelectric Properties of p-Type Bi0.5Sb1.5Te3-Cu8GeSe6 Composite Materials.

Bismuth-telluride-based thermoelectric materials have been applied in active room-temperature cooling, but the mediocre ZT value of ∼1.0 limits the thermoelectric (TE) device's conversion efficiency and determines its application. In this work, we show the obviously improved thermoelectric properties of p-type Bi0.5Sb1.5Te3 by the Cu8GeSe6 composite. The addition of Cu8GeSe6 effectively boosts the carrier concentration and thus limits the bipolar thermal conductivity as the temperature is elevated. With the Cu8GeSe6 content of 0.08 wt %, the hole concentration reaches 5.0 × 1019 cm-3 and the corresponding carrier mobility is over 160 cm2 V-1 s-1, resulting in an optimized power factor of over 42 µW cm-1 K-2 at 300 K. Moreover, the Cu8GeSe6 composite introduces multiple phonon-scattering centers by increasing dislocations and element and strain field inhomogeneities, which reduce the thermal conductivity consisting of a lattice contribution and a bipolar contribution to 0.51 W m-1 K-1 at 350 K. As a consequence, the peak ZT of the Bi0.5Sb1.5Te3-0.08 wt % Cu8GeSe6 composite reaches 1.30 at 375 K and the average ZT between 300 and 500 K is improved to 1.13. A thermoelectric module comprised of this composite and commercial Bi2Te2.5Se0.5 exhibits a conversion efficiency of 5.3% with a temperature difference of 250 K, demonstrating the promising applications in low-grade energy recovery.

Mechanism of Inosine Monophosphate Degradation by Specific Spoilage Organism from Grass Carp in Fish Juice System.

Microbial growth strongly affects the quality and flavor of fish and fish products. This study aimed to explore the role and function of grass carp-borne microorganisms in the degradation of inosine monophosphate (IMP) related compounds in a fish juice system during chill storage (4 °C. Prokaryotic transcriptomic analysis was used to explore the microbial contribution to metabolic pathways and related enzymes. The degree of microbial contribution was verified by the activity of enzymes and metabolite content. Collectively, there were multiple IMP relative product degradation pathways. A. rivipollensis degraded IMP by producing 5'-nucleotidase (5'-NT) while S. putrefaciens degraded IMP mainly by alkaline phosphatase (ALP). Hypoxanthine (Hx) was degraded to uric acid (Ua) induced by P. putida and S. putrefaciens mainly with producing xanthine oxidase (XOD), while A. rivipollensis almost could not produce XOD. This work can used as a guide and provide basic knowledge for the quality and flavor control of aquatic products.

Drivers of spatial and seasonal variations of CO2 and CH4 fluxes at the sediment water interface in a shallow eutrophic lake.

Shallow eutrophic lakes contribute disproportional to the emissions of CO2 and CH4 from inland waters. The processes that contribute to these fluxes, their environmental controls, and anthropogenic influences, however, are poorly constrained. Here, we studied the spatial variability and seasonal dynamics of CO2 and CH4 fluxes across the sediment-water interface, and their relationships to porewater nutrient concentrations in Lake Ulansuhai, a shallow eutrophic lake located in a semi-arid region in Northern China. The mean concentrations of CO2 and CH4 in porewater were 877.8 ± 31.0 µmol L-1 and 689.2 ± 45.0 µmol L-1, which were more than 50 and 20 times higher than those in the water column, respectively. The sediment was always a source of both gases for the water column. Porewater CO2 and CH4 concentrations and diffusive fluxes across the sediment-water interface showed significant temporal and spatial variations with mean diffusive fluxes of 887.3 ±124.7 µmol m-2 d-1 and 607.1 ± 68.0 µmol m-2 d-1 for CO2 and CH4, respectively. The temporal and spatial variations of CO2 and CH4 concentrations in porewater were associated with corresponding variations in dissolved organic carbon and dissolved nitrogen species. Temperature and dissolved organic carbon in surface porewater were the most important drivers of temporal variations in diffusive fluxes, whereas dissolved organic carbon and nitrogen were the main drivers of their spatial variations. Diffusive fluxes generally increased with increasing dissolved organic carbon and nitrogen in the porewater from the inflow to the outflow region of the lake. The estimated fluxes of both gases at the sediment-water interface were one order of magnitude lower than the emissions at the water surface, which were measured in a companion study. This indicates that diffusive fluxes across the sediment-water interface were not the main pathway for CO2 and CH4 emissions to the atmosphere. To improve the mechanistic understanding and predictability of greenhouse gas emissions from shallow lakes, future studies should aim to close the apparent gap in the CO2 and CH4 budget by combining improved flux measurement techniques with process-based modeling.

Application of endoscopic ultrasonography for detecting esophageal lesions based on convolutional neural network.

BACKGROUND: A convolutional neural network (CNN) is a deep learning algorithm based on the principle of human brain visual cortex processing and image recognition. AIM: To automatically identify the invasion depth and origin of esophageal lesions based on a CNN. METHODS: A total of 1670 white-light images were used to train and validate the CNN system. The method proposed in this paper included the following two parts: (1) Location module, an object detection network, locating the classified main image feature regions of the image for subsequent classification tasks; and (2) Classification module, a traditional classification CNN, classifying the images cut out by the object detection network. RESULTS: The CNN system proposed in this study achieved an overall accuracy of 82.49%, sensitivity of 80.23%, and specificity of 90.56%. In this study, after follow-up pathology, 726 patients were compared for endoscopic pathology. The misdiagnosis rate of endoscopic diagnosis in the lesion invasion range was approximately 9.5%; 41 patients showed no lesion invasion to the muscularis propria, but 36 of them pathologically showed invasion to the superficial muscularis propria. The patients with invasion of the tunica adventitia were all treated by surgery with an accuracy rate of 100%. For the examination of submucosal lesions, the accuracy of endoscopic ultrasonography (EUS) was approximately 99.3%. Results of this study showed that EUS had a high accuracy rate for the origin of submucosal lesions, whereas the misdiagnosis rate was slightly high in the evaluation of the invasion scope of lesions. Misdiagnosis could be due to different operating and diagnostic levels of endoscopists, unclear ultrasound probes, and unclear lesions. CONCLUSION: This study is the first to recognize esophageal EUS images through deep learning, which can automatically identify the invasion depth and lesion origin of submucosal tumors and classify such tumors, thereby achieving good accuracy. In future studies, this method can provide guidance and help to clinical endoscopists.

Effect of the Partial Substitution of Sodium Chloride on the Gel Properties and Flavor Quality of Unwashed Fish Mince Gels from Grass Carp.

Excessive salt is usually required to maintain good gel properties and quality characteristics for unwashed fish mince gels (UFMG). This study aimed to investigate the effects of partial sodium chloride substitution (30%) with different substitutes (potassium chloride, disodium inosine-5'-monophosphate, basil) on the gel and flavor properties of UFMG from Ctenopharyngodon idellus. The results indicated that the texture and gel strength of NK (30% NaCl was replaced with 30% KCl) were fairly similar to that of N group (NaCl only), and the whiteness had improved significantly (p < 0.05), while the product eventually yielded a certain bitter taste. The addition of disodium inosine-5'-monophosphate (DIMP) significantly (p < 0.05) increased the hardness, chewiness, buriedness degree of tryptophan and gel strength, decreased the content of α-helix structure in the gels, while less change occurred in gel whiteness and network structure. Basil significantly (p < 0.05) reduced the buriedness degree of tryptophan, gel strength and whiteness, and deteriorated the gel structure. Nevertheless, the addition of DIMP or basil reduced the bitterness induced by KCl and improved the overall acceptability scores of gels of the N group. Moreover, there was no distinct difference in moisture content and water-holding capacity between all groups. Therefore, replacing sodium chloride in UFMG with 25% potassium chloride and 5% DIMP may be an ideal sodium salt substitution strategy.

Exploration of the roles of spoilage bacteria in degrading grass carp proteins during chilled storage: A combined metagenomic and metabolomic approach.

Protein degradation1 caused by spoilage bacteria is highly related to fish quality deterioration during chilled storage. However, the exact roles of bacteria in degrading grass carp proteins are not fully known. In this work, we used metagenomics to analyze the microbiota composition in grass carp fillets, construct protein degrading pathways, and calculate taxonomic contributions to protein degrading functions. Besides, three dominant bacteria species were isolated and inoculated into sterile grass carp flesh, respectively. LC-MS-based untargeted metabolomics was then used to detect protein degradation metabolites produced by the inoculated bacteria. Combining the results of metagenomics and metabolomics, we found 1) Shewanella putrefaciens was active in hydrolyzing fish proteins (especially collagens) and produced quantities of putrescine through the arginine decarboxylase pathway; 2) Pseudomonas putida had potent potentials in utilizing oligopeptides and free amino acids; 3) Serine was a potential energy source for microbial growth and it was largely consumed by spoilage bacteria; 4) S. putrefaciens could form a metabiosis relationship with P. putida, due to their complementary roles in degrading fish proteins. Finally, we concluded that S. putrefaciens had the strongest spoilage potential among tested bacteria, suggesting the importance of S. putrefaciens inhibition in fish quality preservation. Meanwhile, this study contributed to a better understanding of microbial roles in fish spoilage and provided useful information for the development of new preservation methods.

Spoilage-related microbiota in fish and crustaceans during storage: Research progress and future trends.

Fish and crustaceans are highly perishable due to microbial growth and metabolism. Recent studies found that the spoilage process of fish and crustaceans is highly related to their microbiota composition. Microbiota of fish and crustaceans changes dramatically during storage and can be influenced by many factors (e.g., aquaculture environment, handling process, storage temperature, and various quality control techniques). Among them, many quality control techniques have exhibited efficient effects on inhibiting spoilage bacteria, regulating microbiota composition, and retarding quality deterioration. In this article, we elucidate the relationship between microbiota composition and fish/crustacean spoilage, demonstrate influencing factors of fish/crustaceans microbiota, and review various quality control techniques (especially plant-derived preservatives) including their preservative effects on microbiota and quality of fish and crustaceans. Besides, present and future trends of various detective methods used in microbiota analysis are also compared in this review, so as to provide guides for future microbiota studies. To conclude, novel preservation techniques (especially plant-derived preservatives) and hurdle technologies are expected to achieve comprehensive inhibitory effects on spoilage bacteria. Efficient delivery systems are promising in improving the compatibility of plant-derived preservatives with fish/crustaceans and enhancing their preservative effects. Besides, spoilage mechanisms of fishery products that involve complex metabolisms and microbial interactions need to be further elucidated, by using omics technologies like metagenomics, metatranscriptomics, and metabolomics.

Biochemical changes and amino acid deamination & decarboxylation activities of spoilage microbiota in chill-stored grass carp (Ctenopharyngodon idella) fillets.

This study aimed to reveal amino acid deamination and decarboxylation activities of spoilage microbiota in chill-stored grass carp fillets. Results showed that microbial deamination activities of umami/sweet-taste amino acids were higher than that of bitter-taste amino acids. The total deamination activity of tested amino acids decreased during the late period of storage, which inhibited the increase of ammonia in fish flesh. Microbial decarboxylation activity of ornithine was much higher than lysine and histidine, which was consistent with the rapid increase of putrescine in fish fillets. Meanwhile, putrescine could be produced in large quantities through arginine deiminase pathway of spoilage bacteria. Glucose utilization by spoilage microbiota was active during the late period of storage, which was consistent with the rapid consumption of lactate and total sugar in fish flesh. Overall, results of this study could be beneficial for revealing fish spoilage mechanisms and providing theoretical guidance for developing fish preservation technologies.

Assessment of bacterial contributions to the biochemical changes of chill-stored blunt snout bream (Megalobrama amblycephala) fillets: Protein degradation and volatile organic compounds accumulation.

In this study, we evaluated the contributions of three bacteria (Pseudomonas versuta, Shewanella putrefaciens, and Aeromonas sobria) to the proteolysis, biogenic amines formation, volatile organic compounds accumulation, lipid oxidation, nucleotide catabolism, discoloration, and water migration of bream flesh during chilled storage. The results showed that P. versuta exhibited hydrolyzing activity against sarcoplasmic proteins, and all three strains could degrade myofibrillar proteins, specifically actin. The highest producer of putrescine was S. putrefaciens, which reached a maximum level 5.05 mg/kg after 14 days. Compared with the A. sobria group, hypoxanthine riboside degraded faster in samples inoculated with P. versuta or S. putrefaciens, A. sobria, P. versuta, and S. putrefaciens were responsible for the production of alcohol and aldehydes, whereas only S. putrefaciens produced thiophene and partial esters. Fish flesh inoculated with P. versuta, S. putrefaciens, and A. sobria presented slight green, yellow, and pink discoloration, respectively.

Effect of grape seed extract on quality and microbiota community of container-cultured snakehead (Channa argus) fillets during chilled storage.

Herein, the effects of grape seed extract (GSE) on the microflora and biochemical changes of container cultured snakehead (Channa argus) fillets during 11 days of chilled storage were investigated. The sensory analysis, the total number of viable colonies, the total amount of volatile basic nitrogen, and k-value analysis revealed that GSE retarded the deterioration of snakehead fillets. The degradation of inosine 5'-monophosphate and the accumulation of inosine and hypoxanthine in the GSE group were slower than these in the control group. Moreover, GSE treatment effectively decreased the accumulation of putrescine, cadaverine, and histamine. Illumina-MiSeq high throughput sequencing results showed that GSE inhibited the growth of Aeromonas on snakehead fillets. Based on the microbial enumeration, sensory analysis, and k-value, GSE prolonged the shelf life of fillets for 3 days, suggesting its potential for snakehead fillets preservation.

TMT-based proteomic analysis of the fish-borne spoiler Pseudomonas psychrophila subjected to chitosan oligosaccharides in fish juice system.

P. psychrophila is implicated in fish spoilage especially under cold storage. In the present study, tandem mass tag (TMT) quantitative proteomic analysis was performed to clarify the molecular mechanism for the inhibitory effect of chitosan oligosaccharides (COS) against P. psychrophila in fish juice system. The MIC and MBC of the COS against P. psychrophila were 6 and 8 mg/mL, respectively. Compared with the untreated control, a total of 370 proteins (163 up-regulated and 207 down-regulated) were identified as differentially expressed proteins (DEPs, >1.5-fold or < 0.67-fold, P < 0.05) in P. psychrophila when exposed to 6 mg/mL COS. Bioinformatics analysis indicated that the DEPs were mainly involved in the cell wall/membrane, cell motility, and electron-transport chain; DNA replication, RNA transcription and translation, posttranslational modifications of proteins; TCA cycle, and the transport and metabolism of amino acid, carbohydrate, and ion. The scanning electron microscope (SEM) and fourier-transform infrared spectroscopy (FT-IR) analysis further validated that cell structure especially the cell wall/membrane was damaged after COS treatment. The results in this study presented an important step toward understanding the response of P. psychrophila cells to COS at the proteome level.

Effects of ethyl lauroyl arginate hydrochloride on microbiota, quality and biochemical changes of container-cultured largemouth bass (Micropterus salmonides) fillets during storage at 4 °C.

This study aimed to investigate preservative effects of ethyl lauroyl arginate hydrochloride (LAE) on microbiota, quality, and physiochemical changes of container-cultured largemouth bass fillets stored at 4 °C. The results showed LAE treatment was effective in reducing bacterial growth and attenuating physiochemical changes (flesh color, trichloroacetic acid (TCA)-soluble peptides, total volatile basic nitrogen (TVB-N), ammonia concentration, and biogenic amines) of bass fillets, while had relatively weak effect on the degradation of ATP-related compounds. As a result, LAE treatment retarded the deterioration of sensory attributes, and thus prolonged the shelf-life of largemouth bass fillets for 4 days. In addition, LAE treatment decreased the relative abundance of Pseudomonas in bass fillets, and thus changed the microbial composition. Moreover, correlation analysis between physiochemical changes and bacterial genera showed that Pseudomonas was well correlated with TCA-soluble peptides, TVB-N, ammonia, putrescine and histamine, while Aeromonas tended to have strong potentials in producing ammonia and cadaverine.

BldD, a master developmental repressor, activates antibiotic production in two Streptomyces species.

BldD generally functions as a repressor controlling morphological development of Streptomyces. In this work, evidences that BldD also activates antibiotic production are provided. In Streptomyces roseosporus (which produces daptomycin widely used for treatment of human infections), deletion of bldD notably reduced daptomycin production, but enhanced sporulation. BldD stimulated daptomycin production by directly activating transcription of dpt structural genes and dptR3 (which encodes an indirect activator of daptomycin production), and repressed its own gene. BldD-binding sites on promoter regions of dptE, dptR3, and bldD were all found to contain BldD box-like sequences, facilitating prediction of new BldD targets. Two Streptomyces global regulatory genes, adpA and afsR, were confirmed to be directly activated by BldD. The protein AfsR was shown to act as an activator of daptomycin production, but a repressor of development. BldD directly represses nine key developmental genes. In Streptomyces avermitilis (which produces effective anthelmintic agents avermectins), BldD homolog (BldDsav) directly activates avermectin production through ave structural genes and cluster-situated activator gene aveR. This is the first report that BldD activates antibiotic biosynthesis both directly and via a cascade mechanism. BldD homologs are widely distributed among Streptomyces, our findings suggest that BldD may activate antibiotic production in other Streptomyces species.

Biochemical changes induced by dominant bacteria in chill-stored silver carp (Hypophthalmichthys molitrix) and GC-IMS identification of volatile organic compounds.

To evaluate the spoilage potential of dominant bacteria (Aeromonas allosaccharophila, Pseudomonas psychrophila, and Shewanella putrefaciens) isolated from spoiled silver carp (Hypophthalmichthys molitrix) fillets, biochemical changes including protein degradation, trichloroacetic acid (TCA)-soluble peptides, total volatile basic nitrogen (TVB-N), biogenic amines, nucleotide catabolism, and volatile organic compounds were examined in single-species inoculated silver carp flesh for 14 days at 4 °C. P. psychrophila exhibited the strongest proteolytic activity, which resulted in the highest concentrations of TCA-soluble peptides and TVB-N. S. putrefaciens was responsible for the production of putrescine and cadaverine and led to the fastest degradation of hypoxanthine riboside (HxR). At the end of storage, P. psychrophila was the main producer of ketones, especially the C7-C9 ketones, while sulfur compounds were released primarily by S. putrefaciens. Moreover, 1-propanol, butanone, 2-hexanone, methyl isobutyl ketone, dimethyl sulfide, and dimethyl disulfide increased gradually with storage time, suggesting their potential as spoilage markers for freshness/spoilage monitoring. P. psychrophila possessed the strongest spoilage potential in the fish matrix, followed by S. putrefaciens, whereas A. allosaccharophila showed a very low spoilage potential. In conclusion, P. psychrophila and S. putrefaciens were identified as the specific spoilage organisms (SSOs) of silver carp, suggesting that preservation researchers should focus on these two spoilage contributors in future studies. This research contributes to a deeper understanding of silver carp spoilage and to the development of methods and tools to improve fish quality management.

Effect of ε-polylysine and ice storage on microbiota composition and quality of Pacific white shrimp (Litopenaeus vannamei) stored at 0 °C.

This study evaluated the effects of ε-Polylysine and ice storage on microbiota composition and quality attributes of Pacific white shrimp stored at 0 °C. The sensorial shelf-life of control, 0.1% ε-Polylysine treated group, and ice stored group were 5, 8, and 7 days, respectively. Microbiota composition was explored by the Illumina-MiSeq high throughput sequencing targeting of 16S rRNA genes. At the time of sensory rejection, Pseudoalteromonas, followed by Candidatus Bacilloplama and Psychromonas, were the dominant microbiota in spoiled control samples on day 5. However, 0.1% ε-Polylysine inhibited the growth of Pseudoalteromonas and Psychromonas. Consequently, Candidatus Bacilloplama followed by Aliivibrio became the dominant microbiota in the ε-Polylysine treated group on day 8. Meanwhile, Aliivibrio, followed by Moritella and Pseudoalteromonas were the dominant microbiota in ice stored samples on day 7. Furthermore, due to the modulating effect of ε-Polylysine and ice storage on microbiota, chemical changes of the treated groups were slower, which was reflected as lower concentrations of total volatile basic nitrogen, putrescine, cadaverine, and hypoxanthine, and higher contents of inosine 5'-monophosphate and hypoxanthine riboside at the end of storage. In conclusion, ε-Polylysine and ice storage altered the microbiota composition and delayed quality deterioration of Pacific white shrimp.

Effects of pomegranate peel extract on quality and microbiota composition of bighead carp (Aristichthys nobilis) fillets during chilled storage.

This study aimed to investigate effects of aqueous pomegranate peel extract (APPE) and ethanolic pomegranate peel extract (EPPE) on microbiota and changes in quality of bighead carp (Aristichthys nobilis) fillets stored at 4 °C. The results showed that pomegranate peel extract (PPE, which includes both APPE and EPPE) retarded the deterioration of sensory quality and flesh color, inhibited the growth of spoilage bacteria, and attenuated the production of biogenic amines, total volatile basic nitrogen (TVB-N), and the degradation of ATP-related compounds. Moreover, EPPE performed better in color attributes and biogenic amines, but APPE was more effective in retarding the increase of TVB-N and K-value. High-throughput sequencing results showed that microbial composition of all samples became less diverse as storage time increased. For the control group, Acinetobacter was predominant in the middle-period of storage, while Pseudomonas, Aeromonas, and Shewanella became predominant at the end of storage. Additionally, PPE decreased the relative abundance of Acinetobacter in the middle-period of storage, and thus changed the microbial composition. Based on our assessments of quality and microbial analysis, PPE prolonged the shelf-life of bighead carp fillets for about 2 days, and it has the potential to become a promising preservative in aquatic products.