N-glycoproteomic profiling reveals structural and functional alterations in yellow primary preserved egg white under saline-alkali treatment.

The posttranslational N-glycosylation of food proteins is important to their structure and function. However, the N-glycoproteomics of yellow preserved egg white were rarely reported. This study explored the changes of N-glycoproteome in yellow preserved eggs white after salt and alkali treatment. A total of 213 N-glycosites were identified on 102 glycoproteins, revealing prevalent glycosylation motifs and multiple N-glycosites within proteins. Salt and alkali treatment significantly altered the glycosylation patterns, impacting major proteins differently. GO analysis indicated the roles of differentially expressed glycoproteins in responding to stimuli and biological regulation. KEGG analysis emphasized the importance of salivary secretion pathway in enzyme secretion and peptide generation. Protein domain analysis highlighted the downregulation of Serpin. Protein-protein interaction networks revealed Apolipoprotein B as central players. This study provides essential structural information on the glycosylation modifications of egg white proteins, contributing to our understanding of the mechanisms behind the functional properties of preserved eggs.

Exploring the heterogeneity of community and function and correspondence of "species-enzymes" among three types of Daqu with different fermentation peak-temperature via high-throughput sequencing and metagenomics.

The enzyme activity of Daqu is an important prerequisite for defining it as a Baijiu starter. However, little is known about the functional species related to enzymes in different types of Daqu at the metagenomic level. Therefore, we analyzed the differences in enzymatic properties, microbial composition and metabolic function of three types of Daqu, namely high-, medium- and low-temperature Daqus (HTD, MTD and LTD), by combining chemical feature and multi-dimensional sequencing. The results showed that both liquefaction, saccharification, fermentation and esterification powers were remarkably weaker in HTD compared to MTD and LTD. Totally, 30 bacterial and 5 fungal phyla were identified and significant differences in community structures were also observed among samples, with Brevibacterium/Microascus, Pseudomonas, and Lactobacillus/Saccharomycopsis identified as biomarkers for HTD, MTD and LTD, respectively. Additionally, the importance of deterministic assembly in bacterial communities was proportional to the fermentation peak-temperature, while stochastic assembly dominated in fungal ones. Metagenomics analysis indicated eukaryota (>80 %, mainly Ascomycota) predominated in HTD and MTD while bacteria (54.3 %, mainly Actinobacteriota) were more abundant in LTD. However, the functional profiles and pathways of MTD and LTD were more similar, and the synthesis and metabolism of carbohydrates and amino acids were the crucial biological functions of all samples. Finally, the relationship between species and enzymes in different samples was constructed and the functional species in LTD and MTD were more diverse than HTD, which elucidated the functional species associated with enzyme activity in each type of Daqu. These results will greatly enrich our understanding of the core functional species in three typical Daqu, which provide available information for rational regulation of Daqu quality and the Baijiu fermentation.

Retraction notice to "Study on the quality formation mechanism of Zao chili with enhanced fermentation by Lactipllantbacillus plantarum 5-1" [Food Chemistry: X 17 (2023) 100626].

[This retracts the article DOI: 10.1016/j.fochx.2023.100626.].

Bioaccumulation and elimination, acute toxicity analysis and risk assessment of diflubenzuron in common carp (Cyprinus carpio).

Diflubenzuron has been applied in agriculture and aquaculture, and its residues in ecological environment and food chain could result in chronic exposure and long-term toxicity effects for human health. However, limited information is available regarding diflubenzuron levels in fish and associated risk assessment. This study performed the analysis for dynamic bioaccumulation and elimination distribution of diflubenzuron in carp tissues. The results indicated that diflubenzuron was absorbed and enriched by fish body along with higher enrichment in lipid-rich tissues of fish. The peak concentration in carp muscle reached 6-fold of diflubenzuron concentration in aquaculture water. The median lethal concentration (LC50) of diflubenzuron at 96 h was 12.29 mg/L, presented low toxicity to carp. Risk assessment results showed that the chronic risk from dietary exposure to diflubenzuron through carp consumption for Chinese residents of children and adolescents, adults and elderly people were acceptable, while posed a certain risk for young children. This study provided the reference for pollution control, risk assessment and scientific management of diflubenzuron.

Quantitative proteomics study on the changes of egg white of yellow preserved primary chicken eggs soaked in alkali solution.

In order to investigate the changes of egg white of primary chicken eggs after being soaked in alkali solution, the tandem mass tags (TMT)-labeled quantitative proteomic technology combined with bioinformatics was conducted in this study. The results indicated that 100 differentially expressed proteins (DEPs) in yellow preserved primary egg white (YPPEW), 75 of which were highly and significantly correlated with the quality traits of YPPEW (| r | ≥ 0.9000, P < 0.01). Most of DEPs were involved in cellular processes by binding in extracellular space. Six pathways revealed the potential anti-inflammatory, anti-virus, anti-cancer and neuromodulatory mechanism of YPPEW. The current research provided a theoretical basis for the further study on YPPEW.

Analysis of the formation mechanism of volatile and non-volatile flavor substances in corn wine fermentation based on high-throughput sequencing and metabolomics.

The purpose of this study was to reveal the relationship between core microorganisms and flavor substances in the fermentation process of corn wine. Microbial diversity, volatile and non-volatile flavor substances were detected by high-throughput sequencing (HTS), headspace solid phase micro-extraction gas chromatography-mass spectrometry (HS-SPME/GC-MS) and gas chromatography time of flight mass spectrometry (GC-TOF-MS). High performance liquid chromatography (HPLC) was used to detect organic acids in corn wine fermentation, and its physiochemical properties were tracked. The results showed that physiochemical factors changed obviously with fermentation time. Bacillus, Prevotella_9, Acinetobacter and Gluconobacter were the predominant bacterial. Rhizopus and Saccharomyces were the dominant fungi. Acetic acid and succinic acid were important organic acids in corn wine. According to variable importance of projection (VIP) > 1 and P < 0.05, 24 volatile flavor substances with significant difference were screened out from 52 volatile flavor substances. Similarly, 25 non-volatile flavor substances with significant differences were screened out from the 97 reliable metabolites identified by 223 chromatographic peaks. Eight key metabolic pathways were enriched from 25 non-volatile flavor substances according to path influence values > 0.1 and P < 0.05. Based on Two-way Orthogonal Partial Least Squares (O2PLS) model and Pearson correlation coefficient, Saccharomyces, Rhizopus, uncultured_bacterium, Aneurinibacillus, Wickerhamomyces and Gluconobacter may be the potential volatile flavor-contributing microorganism genus in corn wine. The Pearson correlation coefficient showed that Saccharomyces was significantly positively correlated with malic acid, oxalic acid, valine and isoleucine, and Rhizopus was positively correlated with glucose-1-phosphate and alanine. These findings enhanced our understanding of the formation mechanism of flavor substances in corn wine and provided the theoretical basis for stabilizing flavor quality of corn wine.

Study on the correlation between microbial communities with physicochemical properties and flavor substances in the Xiasha round of cave-brewed sauce-flavor Baijiu.

The Chishui River basin is the main production area of the sauce-flavor Baijiu. Due to the particularity of sauce-flavor Baijiu technology, a large site of workshops needs to be built for brewing and storage. Therefore, used the natural karst caves of Guizhou province to manufacture the sauce-flavor Baijiu, which has enriched the connotation of sauce-flavor Baijiu and saved valuable land resources. In this study, the fermentation grains in the seven stages during the Xiasha round of the cave-brewed sauce-flavor Baijiu (CBSB) were detected using a combination of physicochemical analysis, Headspace solid-phase microextraction gas chromatography-mass detection, and Illumina HiSeq sequencing methods. The results showed Unspecified_Leuconostocaceae, Weissella, Unspecified_Bacillaceae, Saccharomycopsis, Thermomyces, and Unspecified_Phaffomycetaceae were the main bacterial and fungal genera in the stacking fermentation (SF). In the cellar fermentation (CF), the Lactobacillus, Unspecified_Lactobacillaceae, Thermoactinomyces, Saccharomycopsis, Unspecified_Phaffomycetaceae, and Wickerhamomyces were the main bacterial and fungal genera. A total of 72 volatiles were detected in the fermented grains. Linear discriminant analysis Effect Size (LEfSe) identified 23 significantly different volatile metabolites in the fermentation process, including 7 esters, 6 alcohols, 4 acids, 3 phenols, 1 hydrocarbon, and 2 other compounds. Redundancy analysis was used to explore the correlation between dominant microbial genera and physicochemical properties. Starch was the main physicochemical property affecting microbial succession in the SF. Acidity, moisture, and reducing sugar were the main driving factors of microbial succession in the CF. The Pearson correlation coefficient revealed the correlation between dominant microbial genera and significantly different volatile flavor substances. A total of 18 dominant microbial genera were associated with significantly different volatile metabolites, Lactobacillus, Weissella, Wickerhamomyces, and Aspergillus were shown to play crucial roles in metabolite synthesis. On this basis, a metabolic map of the dominant microbial genera was established. This study provides a theoretical basis for the production and quality control of sauce-flavor Baijiu brewed in natural karst caves and lays a foundation for studying the link between flavor formation and microorganisms.

Study on the quality formation mechanism of Zao chili with enhanced fermentation by Lactipllantbacillus plantarum 5-1.

Zao Chili (ZC) is a traditional fermented pepper, which plays an important role in Chinese cooking. The aim of this study was to elucidate the effect of Lactipllantbacillus plantarum 5-1 on the physicochemical properties, metabolite and microbiota profiling of ZC. The physicochemical factors changed regularly with the fermentation time. In the microbial communities, Lactobacillus, Weissella, Enterobacter, Gibberella, Fusarium, Zygosaccharomyces and Pichia were the dominant genera. 7 kinds of organic acids were detected in the whole fermentation process of ZC, but only 5 kinds changed significantly. Based on the OPLS-DA model with VIP > 1 and ANOVA with P < 0.05, 33 volatile flavor compounds with significant differences were screened out of 89. According to the redundancy analysis (RDA), fungi mainly contributed to soluble solids, while bacteria mainly contributed to pH. Lactobacillus, Weissella, Enterbacter and Zygosaccharomyces may be the potential flavor contributing microorganisms in the fermentation process of ZC by the Spearman correlation coefficient. A total of 11 main metabolic pathways were obtained by KEGG enrichment analysis of 89 volatile flavor compounds and 7 organic acids. Therefore, this study further enhanced our understanding of the flavor quality formation mechanism of Lactipllantbacillus plantarum in ZC, and providing a theoretical basis for improving the flavor quality of ZC.

Effects of Jiuqu inoculating Rhizopus oryzae Q303 and Saccharomyces cerevisiae on chemical components and microbiota during black glutinous rice wine fermentation.

In this study, the physicochemical properties, metabolites, sensory characteristics, and microbiota of black glutinous rice wine (BGRW) during traditional fermentation (TF) and inoculated fermentation (IF) were investigated, and their correlation relationships were revealed. Results indicated that IF promoted total sugar utilization and ethanol and esters synthesis in BGRW. Altogether 67 reliable metabolites were identified, 36 of which were labeled components, primarily esters (OAV > 1). Meanwhile, the concentrations of ethanol, esters, and total flavor on the 11th day of IF were close to those on the 22nd day of TF. Combined with the sensory description indicated that the IF could improve the quality of BGRW. Besides, TF contains vast unfavorable microorganisms, such as Chaetomium, Penicillium, Stachybotrys, and Trichocladium. Therefore, IF can accelerate the fermentation and enhance the flavor of BGRW, and inhibit the growth of pathogenic and spoilage organisms. Finally, Pearson's correlation analysis demonstrated that Saccharomyces, Rhizopus, Lactobacillus, Aspergillus, and Bacillus were the pivotal functional microorganisms in BGRW. The study provided scientific and effective basis for improving the quality, shortening the fermentation cycle, and controlling pathogenic and spoilage organisms of BGRW.

Effects of Pediococcus acidilactici and Rhizopus Oryzae on microbiota and metabolomic profiling in fermented dry-cure mutton sausages.

Traditional fermentation of dry mutton sausages (DMSs) commonly causes some quality problems. In this study, high-throughput sequencing (HTS) and metabolomics were used to study the microorganisms and metabolites of DMSs produced by mixed strains of Pediococcus acidilactici and Rhizopus Oryzae, to discover the effect of inoculated fermentation (IF) on the metabolites of DMSs. A total of 92 volatile metabolites and 58 non-volatile significantly different metabolites were identified in DMSs. After inoculated fermentation, the volatile types increased, and the total contents of aldehydes and esters were enhanced at the end of fermentation. In addition, the levels of amino acids, fatty acids, palmitoyl carnitine, acetyl-l-carnitine, and betaine were also improved. The correlation analysis showed that the P. acidilactici and R. Oryzae were highly correlated with a variety of metabolites. Together, these findings provide excellent strain resources for improving the quality of mutton sausages.

Acute toxicity, bioaccumulation and elimination of prometryn in tilapia (Oreochromis niloticus).

Tilapia juvenile (Oreochromis niloticus) (mean weight 50.00 ± 10.00 g) were aqueous exposed to different concentrations of the herbicide prometryn to investigate its acute toxicity, bioaccumulation and uptake and elimination rates. First, a 96-h acute toxicity test was carried out. The resulting 96 h LC50 was 5.49 mg/L, and the 96 h LC10 was 5.02 mg/L. Then, fish were exposed to 0.55 mg/L (1/10 96 h LC50) and 0.055 mg/L (1/100 96 h LC50) of prometryn solution for 28 days, followed by 14 days of elimination in clean groundwater. The result shows that in both water and tissues, prometryn concentrations fluctuated during the exposure period, indicating that steady state was not reached. The bioaccumulation of prometryn was the highest in liver, followed by gill, muscle and blood. The accumulated concentration levels in various tissues were always higher in the high concentration compared to the low concentration. The highest accumulated concentration of prometryn in various tissues in the 0.055 mg/L treatment were for muscle: 0.136 ± 0.0616 mg/kg (1 d), liver: 3.74 ± 2.95 mg/kg (7 d), gill: 0.971 ± 1.45 mg/kg (1 d) and blood: 0.0716 ± 0.0669 mg/kg (22 d). In the 0.55 mg/L treatment, the highest levels were for muscle: 1.27 ± 0.284 mg/kg (1 d), liver: 16.9 ± 12.7 mg/kg (7 d), gill: 8.11 ± 3.02 mg/kg (1 d) and blood: 0.751 ± 0.0775 mg/kg (22 d). The highest bioconcentration factor (BCF) of 93.1 was observed in the liver when exposed to the low concentration. Besides, for other tissues, the highest BCF were for muscle: 5.76, gill: 32.3 and blood: 2.91, all observed in the 0.55 mg/L treatment. Most of the accumulated prometryn was removed from all tissues within 24 h after the organisms were transferred to clean water. However, management of using prometryn in China aquaculture should be improved to prevent possible ecotoxicological effects and ensure food safety.

Pharmacokinetics and residue elimination of norfloxacin in rainbow trout (Oncorhynchus mykiss).

We studied the metabolism and elimination of norfloxacin in rainbow trout (Oncorhynchus mykiss) following a single oral administration of 50 mg/kg at 15 ± 2°C. Norfloxacin was measured by high-performance liquid chromatography-tandem mass spectrometry in plasma, muscle, liver, kidney, skin and remainder tissues, and the concentrationtime curve was characterized by a double peak. The drug was absorbed rapidly; the first peak appeared within 4 h, and the second peak appeared within 24 h in all substrates tested. The maximal concentrations in plasma, muscle, liver and kidney were 0.468 mg/L, 14.146 mg/kg, 6.445 mg/kg and 0.977 mg/kg, respectively. The distribution half-life was 5.814, 9.026, 17.027 and 1.004 h, respectively. The elimination half-life was 41.205, 41.667, 44.896 and 54.908 h, respectively. Using the kidney as the reference tissue for norfloxacin monitoring in aquaculture and 2 µg/kg as a maximum residue limit standard, it takes 555 temperature-day (°C days) for norfloxacin to be completely eliminated from rainbow trout.

Biodegradation and metabolic pathway of sulfamethoxazole by Sphingobacterium mizutaii.

Sulfamethoxazole (SMX) is the most commonly used antibiotic in worldwide for inhibiting aquatic animal diseases. However, the residues of SMX are difficult to eliminate and may enter the food chain, leading to considerable threats on human health. The bacterial strain Sphingobacterium mizutaii LLE5 was isolated from activated sludge. This strain could utilize SMX as its sole carbon source and degrade it efficiently. Under optimal degradation conditions (30.8 °C, pH 7.2, and inoculum amount of 3.5 × 107 cfu/mL), S. mizutaii LLE5 could degrade 93.87% of 50 mg/L SMX within 7 days. Four intermediate products from the degradation of SMX were identified and a possible degradation pathway based on these findings was proposed. Furthermore, S. mizutaii LLE5 could also degrade other sulfonamides. This study is the first report on (1) degradation of SMX and other sulfonamides by S. mizutaii, (2) optimization of biodegradation conditions via response surface methodology, and (3) identification of sulfanilamide, 4-aminothiophenol, 5-amino-3-methylisoxazole, and aniline as metabolites in the degradation pathway of SMX in a microorganism. This strain might be useful for the bioremediation of SMX-contaminated environment.

Lacticaseibacillus casei ATCC 393 Cannot Colonize the Gastrointestinal Tract of Crucian Carp.

Lactic acid bacteria (LAB) are commonly applied to fish as a means of growth promotion and disease prevention. However, evidence regarding whether LAB colonize the gastrointestinal (GI) tract of fish remains sparse and controversial. Here, we investigated whether Lacticaseibacillus casei ATCC 393 (Lc) can colonize the GI tract of crucian carp. Sterile feed irradiated with 60Co was used to eliminate the influence of microbes, and 100% rearing water was renewed at 5-day intervals to reduce the fecal-oral circulation of microbes. The experiment lasted 47 days and was divided into three stages: the baseline period (21 days), the administration period (7 days: day -6 to 0) and the post-administration period (day 1 to 19). Control groups were fed a sterile basal diet during the whole experimental period, whereas treatment groups were fed with a mixed diet containing Lc (1 × 107 cfu/g) and spore of Geobacillus stearothermophilus (Gs, 1 × 107 cfu/g) during the administration period and a sterile basal diet during the baseline and post-administration periods. An improved and highly sensitive selective culture method (SCM) was employed in combination with a transit marker (a Gs spore) to monitor the elimination of Lc in the GI tract. The results showed that Lc (<2 cfu/gastrointestine) could not be detected in any of the fish sampled from the treatment group 7 days after the cessation of the mixed diet, whereas Gs could still be detected in seven out of nine fish at day 11 and could not be detected at all at day 15. Therefore, the elimination speed of Lc was faster than that of the transit marker. Furthermore, high-throughput sequencing analysis combined with SCM was used to reconfirm the elimination kinetics of Lc in the GI tract. The results show that the Lc in the crucian carp GI tract, despite being retained at low relative abundance from day 7 (0.11% ± 0.03%) to 21, was not viable. The experiments indicate that Lc ATCC 393 cannot colonize the GI tract of crucian carp, and the improved selective culture in combination with a transit marker represents a good method for studying LAB colonization of fish.

Correlation Between Microbial Diversity and Volatile Flavor Compounds of Suan zuo rou, a Fermented Meat Product From Guizhou, China.

Suan zuo rou (SZR), a traditional fermented meat from Guizhou province, China, is loved by local people for its unique flavor and nutritional value. However, the microbial communities and related flavor characteristics of SZR from different regions of Guizhou are unclear. We studied the correlation between the microbial communities and the physicochemical properties and volatile flavor compounds (VFCs) of 15 SZR samples from three regions in Guizhou province. The microbial community structure of SZR was determined by high-throughput sequencing and VFCs were identified by headspace-solid phase microextraction combined with gas chromatography-mass spectrometry. The results indicated that the microbial communities of SZR varied among the regions, as evidenced by the relative abundance of Weissella, Staphylococcus, Brochothrix, Kazachstania, and Debaryomces. There were also significant differences in pH, water activity, NaCl, and total volatile basic nitrogen (P < 0.05). Based on orthogonal projections to latent structures and Pearson's correlation coefficient, we showed that Wickerhamomyces, Kazachstania, Lactobacillus, Weissella, Brochothrix, Debaryomyces, Staphylococcus, Pediococcus, Pichia, Candida, and Leuconostoc were highly correlated with 48 VFCs (| ρ| > 0.8, P < 0.05). Redundancy analysis showed that most of the dominant bacteria were positively related to water activity, whereas Lactobacillus was positively related with pH, and negatively related with total volatile basic nitrogen.

Determination of Pendimethalin Dynamic Residual Distribution in Crucian Carp Tissues and Associated Risk Assessment.

Pendimethalin has been considered a moderately to extremely toxic compound for fish and aquatic organism. This study developed the determination of dynamic residual distribution for pendimethalin in crucian carp tissues (muscle, liver, kidney, gill, and blood) under semistatic exposure system by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method. The pendimethalin residues in various fish tissues increased initially and then decreased, and the residue amount of pendimethalin varied from tissue to tissue of crucian carp. Particularly, the pendimethalin accumulation in most fish tissues made significant decreases at two-time points. Pendimethalin was initially absorbed and enriched by fish body, and then partial pendimethalin was discharged into the outside environment through the metabolism function of crucian carp. The residue levels of pendimethalin distributed in crucian carp were ranked in the following decreasing order: liver > kidney > gill or muscle > blood, attributed to the fact that pendimethalin tends to accumulate in lipid-rich tissues of fish. Risk assessment results indicated that the chronic risk from dietary exposure to pendimethalin through crucian carp consumption for Chinese residents was acceptable, along with a lower estimated exposure dose (EED) than acceptable daily intake (ADI) and risk quotient (RQ) < 1. This study performed the first analysis for pendimethalin residual distribution in crucian carp tissues under semistatic exposure condition and provided a reference for pollution control and risk assessment of pendimethalin aimed at aquatic products.

Impact of air emissions from shipping on marine phytoplankton growth.

With the rapid expansion of maritime traffic, increases in air emissions from shipping have exacerbated numerous environmental issues, including air pollution and climate change. However, the effects of such emissions on marine biogeochemistry remain poorly understood. Here, we collected ship-emitted particles (SEPs) from the stack of a heavy-oil-powered vessel using an onboard emission test system and investigated the impact of SEPs on phytoplankton growth over the northwest Pacific Ocean (NWPO). In SEP microcosm experiments conducted in oceanic zones with different trophic statuses, the phytoplankton response, as indicated by chlorophyll a (Chl a), has been shown to increase with the proportion of SEP-derived nitrogen (N) relative to N stocks (PSN) in baseline seawater, suggesting that SEPs generally promote phytoplankton growth via N fertilisation. Simulations using an air quality model combined with a ship emission inventory further showed that oxidised N (NOx) emissions from shipping contributed ~43% of the atmospheric N deposition flux in the NWPO. Air emissions from shipping (e.g. NOx and sulphur dioxide) also indirectly enhanced the deposition of reduced N that existed in the atmosphere, constituting ~15% of the atmospheric N deposition flux. These results suggest that the impact of airborne ship emissions on atmospheric N deposition is comparable to that of land-based emissions in the NWPO. Based on the ship-induced PSN in surface seawater calculated by modeling results and World Ocean Atlas 2013 nutrient dataset, and the well-established quantitative relationship between Chl a and PSN obtained from microcosm experiments, we found a noticeable change in surface Chl a concentrations due to N deposition derived from marine traffic in the NWPO, particularly in the coastal waters of the Yellow Sea and open oceans. This work attempts to establish a direct link between marine productivity and air emissions from shipping.

Correlations between microbiota with physicochemical properties and volatile flavor components in black glutinous rice wine fermentation.

Black glutinous rice wine (BGRW) is a popular traditional Chinese rice wine; however, the flavors profiles associated with microbiota changes during its fermentation have not yet been evaluated. In this study, we explored the correlations between microbial communities with physicochemical properties and flavor components during BGRW fermentation. High-throughput sequencing was used to identify the microbial community composition of BGRW at different fermentation stages, and physicochemical properties and volatile flavor compounds (VFCs) were identified via fermentation features testing and headspace solid phase microextraction gas chromatography mass spectrometry. First, we revealed Pantoea and Kosakonia predominated bacterial genera the early stage of BGRW fermentation, Leuconostoc, Pediococcus, Bacillus, and Lactobacillus predominated bacterial genera the later stage, while Rhizopus and Saccharomyces were the predominant fungal genera throughout fermentation. Second, total sugars, titratable acids, pH, ethanol, amino acid nitrogen, and 43 VFCs were detected during fermentation. Twenty-three VFCs were differentially produced according to the linear discriminant analysis effect size method. With the increase of the fermentation time, the kinds and contents of esters and alcohols were also increased, while acids decreased. Moreover, 12 microbial genera, Lactococcus, Pediococcus, Leuconostoc, Lactobacillus, Cronobacter, Pantoea, Weissella, Enterococcus, Rhizopus, Myceliophthora, Cystofilobasidium, and Aspergillus were found to be highly correlated (|ρ| > 0.7 and P < 0.05) with physicochemical properties and VFCs, by redundancy analysis (RDA) and two-way orthogonal partial least squares (O2PLS) analysis. Ultimately, based on the results, a metabolic map of dominant genera in BGRW was established. Our findings provided detailed information on the dynamic changes of physicochemical properties and VFCs and selection of beneficial strains to improve the quality of BGRW.

Dynamics of phytoplankton and nutrient uptake following dust additions in the northwest Pacific.

Dust deposition can supply nutrients that affect marine phytoplankton, but changing trophic statuses of the surface ocean increase the complexity of interpreting the process. In this study, four onboard incubation experiments amended with various nutrients and dust were performed in the Kuroshio Extension (KE) and Kuroshio-Oyashio transition (TR) of the northwest Pacific (NWP), which are characterised by lower and higher trophic statuses, respectively. According to the nutrient-addition experiments, phytoplankton were limited by nitrogen (N) in the KE, and limited by iron (Fe) or co-limited by Fe and phosphorus (P) in the TR. Dust additions supplied a considerable amount of N and Fe but negligible amount of P to stimulate phytoplankton growth, as indicated by chlorophyll a (Chl a) concentration. In the KE incubations, dust additions enhanced the shift of phytoplankton size structure towards larger cells from dominantly pico-sized (0.2-2 µm) Chl a to comparable contributions from each size class (i.e. pico-, nano-: 2-20 µm, micro-: >20 µm). On the basis of the large shift of size structure towards nano- or micro-phytoplankton in the unamended control treatments in the TR, dust additions furtherly promoted the shift towards micro-phytoplankton becoming the dominant contributor to the total Chl a. The collective analysis of the data from experiments in both regions revealed that, the extent of phytoplankton growth stimulation and the shift towards larger cells were enhanced gradually with increasing amounts of nutrient uptake (including N, P, and silicon). The nutrient uptake ratios of phytoplankton converged towards the Redfield ratio in comparison to the wider range of nutrient ratios in the dust-amended seawater. This study suggested consistencies in the dynamic of phytoplankton growth, shift of size structure, and nutrient uptake following dust additions in the KE and TR, although the trophic status and limiting nutrient varied between these two regions.