In this study, the mechanisms underlying feed efficiency (FE) variation in the sea urchin Strongylocentrotus intermedius were investigated by integrating gut microbiota and metabolomic analyses. To accurately measure individual feed intake, a single-circuit recirculating water aquaculture system was developed. After a 25-day feeding trial, 84 individuals were categorized into high-feed efficiency (HFE, low FCR) and low-feed efficiency (LFE, high FCR) groups on the basis of their feed conversion ratio (FCR). 16S rDNA sequencing revealed differences in microbial community structure in the large and small intestines between the groups. The relative abundances of Proteobacteria in the large intestine and Firmicutes in the small intestine were greater in the HFE group. In contrast, the LFE group exhibited elevated levels of Spirochaetota and potentially detrimental taxa such as Ruminococcus_gnavus_group. Functional prediction analysis indicated that microbial biomarkers in the HFE group were enriched in pathways related to carbon metabolism and amino acid biosynthesis. Untargeted metabolomics analysis of coelomic fluid revealed 107 significantly differential metabolites. The key metabolites associated with HFE included PE, LPC, and chamazulene, which are involved in lipid metabolism and redox regulation. Correlation analysis revealed significant interactions between specific gut microbial taxa and these differentially abundant metabolites. This study also revealed functional compartmentalization along the digestive tract: the small intestine was primarily associated with enzymatic digestion, whereas the large intestine was associated with nutrient absorption. These findings suggest that microbiota–metabolite crosstalk plays a crucial role in the regulation of FE, establishing a reliable method for assessing the FE of sea urchins.

Coastal-estuarine wetlands store organic carbon (OC) far in excess of their area, in part because tidal redox oscillations sustain reactive iron phases that bind OC. Aquaculture conversion is the dominant disturbance to these wetlands in China, yet whether it alters the magnitude of iron-bound OC (Fe-OC) or the mechanism by which iron stabilizes OC has remained unresolved. Here we show that conversion does both, and that the mechanistic shift is the more consequential change. Across ten paired natural wetlands and aquaculture ponds spanning tropical to temperate China and three vegetation types (Suaeda salsa, Phragmites australis, mangrove), reclamation lowered soil Fe-OC by 32 to 51% and depleted reactive solid-phase Fe pools (Fed, Feo, Fep). The Fe(III)/Fe(II) ratio declined by 9 to 54%, the molar OC/Fe ratio of Fe-OC fell from above 1 to below 1, and the C/N ratio dropped by 11 to 66%, indicating less OC stabilized per unit reactive Fe. Fourier-transform infrared spectroscopy (FTIR) showed a consistent decline in the aromatic-to-alkoxyl C ratio, evidence that the remaining Fe-OC is structurally less stable. Random-forest and structural-equation analyses revealed a regime shift in the controls on Fe-OC: carbon-supply variables governed Fe-OC in natural wetlands, whereas iron-reactivity variables took over in ponds, and the model explained 68% of Fe-OC variance. These changes were directionally consistent across vegetation types despite divergent pathways, pointing to a cross-system vulnerability of the iron-mediated carbon sink to tidal disconnection. Our study provides process-based evidence that aquaculture-pond retirement and wetland restoration should rebuild tidal connectivity and reactive-iron regeneration, rather than targeting soil-carbon stocks alone.

Wetlands serve as critical reservoirs of soil organic carbon, in which Fe-bound organic carbon (Fe-OC) plays an important role in the long-term preservation of carbon. However, the widespread land-use conversion of estuarine wetlands to aquaculture ponds may disrupt the microbial and enzymatic processes that stabilize Fe-OC, yet the linkages among these three factors remain unclear. This study selected three typical estuarine wetlands in China along with their adjacent aquaculture ponds, to investigate how reclamation affects Fe-OC dynamics by altering the carbon-sequestering microbial community and soil enzyme activities. The results showed that reclamation led to a significant reduction of 57% in Fe-OC content (p < 0.05). This decrease was closely associated with the decline in HCl-extractable Fe (HCl-Fet) and Fe oxides content (p < 0.05), the restructuring of the carbon-sequestering microbial community, and the significant inhibition of key hydrolytic enzymes (p < 0.05). Random Forest analysis identified specific bacterial genera such as Sulfuritortus, β-glucosidase (BG) activity, soil water content, and HCl-Fet as the main factors influencing Fe-OC loss. Integrating the roles of microorganisms, enzymes, and iron, this study provides key insights into the changes in carbon protection mechanisms under land-use change, offering important implications for wetland conservation and sustainable aquaculture management.

Coenzyme Q10 (CoQ10) has attracted widespread attention in recent years due to its momentous physiological functions. Microbial fermentation is the major method in CoQ10 industrial production, and Rhodobacter sphaeroides is the main strain for the production of CoQ10 by fermentation. Optimization of the culture medium is a popular solution to improve the metabolite production. Culture medium is the material basis for microbial growth and product synthesis, of which inorganic salts are a key ingredient. Uniform design (UD), artificial neural network (ANN), and genetic algorithm (GA) are the main research methods. Through uniform design (UD) and artificial neural network/genetic algorithm (ANN-GA) progressive optimization, an optimal formulation of the inorganic salts in fermentation medium was obtained (g·L−1): MgSO4 12, NaCl 2.5, FeSO4 1.6, KH2PO4 0.8, MnSO4 0.1, CaCl2 0.1. Ultimately, the fermentation yield of CoQ10 could reach 255.36 mg·L−1. ANN-GA exhibited a superior prediction capability compared to UD. Compared to UD, the optimization results of ANN-GA had a smaller relative error (ANN-GA 1.23%; UD 3.01%) and a higher increase rate in the fermentation level of CoQ10 (ANN-GA 4.1%; UD 2.04%). R. sphaeroides had a high demand for Mg2+.

Propionic acid (PA), a widely utilized food preservative and mold inhibitor, offers significant advantages when produced via microbial fermentation compared to chemical synthesis, including sustainable raw material utilization, simplified operational conditions, and reduced environmental impact. However, traditional free-cell fermentation faces limitations in productivity and process stability. In this study, sodium alginate and polyvinyl alcohol were utilized as composite carriers, with Propionibacterium acidipropionici FS1026 serving as the target bacterium for the preparation of immobilized pellets for PA fermentation. The conditions for the preparation of these immobilized pellets and the fermentation process for PA production were optimized separately. The results indicated that: (1) the optimal immobilization conditions were as follows: polyvinyl alcohol concentration of 10.8 g/L, sodium alginate concentration of 1.5 g/L, immobilization solution consisting of a mixture of 2 % CaCl2 and 50 g/L boric acid, a bacterial inclusion amount of 12 %, and an immobilization time of 8 h; (2) the optimal medium for PA fermentation using the immobilized cells contained: glucose at 75.41 g/L, yeast powder at 30 g/L, peptone at 16.31 g/L, K2HPO4 at 24 g/L, and MgSO4 at 0.7 g/L; (3) the immobilized cells maintained stable PA production over 10 consecutive fermentation batches, achieving an average yield of 26.31 g/L, thereby confirming operational robustness; (4) optimization of the fermentation process revealed that pH adjustment using ammonia was superior to that using Ca(OH)2, and the optimal glucose replenishment interval was every 24 h, with a replenishment of 35 g/L, resulting in a PA yield of up to 42.76 g/L-significantly higher than the yield from free cell fermentation (20.33 g/L). This study demonstrates that immobilized cell fermentation establishes a novel technical approach for PA production, exhibiting promising industrial scalability and environmental sustainability.

Introduction:This study investigated the effects of Bacillus licheniformis on the water quality, growth performance and bacterial community in Penaeus vannamei aquaculture system. The objective was to elucidate the impact of B. licheniformis on P. vannamei aquaculture from a microbial ecological perspective. This research provided valuable theoretical support for the practical application of B. licheniformis in improving aquaculture practices for P. vannamei. Methods:The design of the aquaculture experiment comprised two groups: a control group (CK) fed a basal diet and a treatment group (PB) was fed the same diet with addition of B. licheniformis (5 × 104 CFU/mL) into the water every 5 days. These groups were systematically evaluated through comprehensive water quality analyses, including pH, ammonia nitrogen, nitrite nitrogen, and Vibrio counts, as well as growth performance assessments such as length, weight, survival rate, yield, and feed conversion ratio (FCR). Additionally, high-throughput sequencing technology was employed to analyze changes in bacterial community structures in both the aquaculture water and the shrimp intestines. Results:The results demonstrated that B. licheniformis significantly improved water quality, promoted shrimp growth, and altered the bacterial community structure: (1) B. licheniformis significantly reduced the concentrations of ammonia nitrogen, nitrite nitrogen, and pathogenic Vibrio counts in the later stages of cultivation (P < 0.05), while significantly promoting shrimp growth; (2) The addition of B. licheniformis increased the diversity and richness of bacteria both in the water and shrimp intestinal tracts, leading to significant changes in bacterial community structure. It also enhanced beneficial bacterial genera such as Gemmobacter, Paracoccus, and Bacillus in the water, while concurrently reducing the potential pathogenic Flavobacterium in the shrimp intestinal tract; (3) The dominant bacterial populations were significantly affected in both water and shrimp intestinal samples. In water, Aurantimicrobium was the predominant genus in both groups, with the PB group showing a notably lower relative abundance. In the shrimp intestines, the CK group was dominated by Gemmobacter and Fluviicola, while Aurantimicrobium prevailed in the PB group. In conclusion, the study revealed the potential of B. licheniformis in shrimp aquaculture by improving water quality, promoting shrimp growth, and modulating bacterial community structure. Discussion:This study demonstrated that B. licheniformis significantly improved water quality and shrimp growth performance in P. vannamei aquaculture. It effectively reduced pH, ammonia and nitrite levels, while also decreasing Vibrio counts, which are critical for disease control. B. licheniformis enhanced microbial diversity in both aquaculture water and shrimp intestines, promoting the abundance of beneficial genera, while reducing potential pathogens. The alteration in bacterial community structure suggests that B. licheniformis plays a pivotal role in maintaining a healthy microbial ecosystem, enhancing shrimp health and growth, and providing an environmentally sustainable alternative to antibiotics in aquaculture practices. These findings underscore the potential of B. licheniformis for improving P. vannamei aquaculture systems.

Estuarine wetlands are critical organic carbon sinks, where Fe oxides bind with organic carbon to form Fe-bound organic carbon (Fe-OC), which plays an important role in carbon sequestration within these ecosystems. The conversion of natural estuarine wetlands into aquaculture ponds leads to notable changes in both the Fe content and the Fe-OC pool. The goal was to reveal the interactions among these bacteria, soil iron, and Fe-OC throughout the transformation process. We analyzed three typical Chinese estuarine wetlands to investigate changes in Fe fractions, Fe-OC and Fe-related bacterial communities (Fe-oxidizing bacteria and Fe-reducing bacteria) during aquaculture pond conversion, along with their interrelationships. After land-use change, Fe-OC and the molar OC:Fe rations (OC:Fe) in all soil layers decreased significantly by over 54

Fructosyltransferase (FTase) is a key glycosidase with hydrolytic and transglycosylation functions that can utilize sucrose to generate oligofructose (FOS), which is extremely important in the food industry as well as in plants and microorganisms. However, there remain significant gaps in our understanding of the catalytic mechanism of FTase, particularly regarding the effect of regulatory mechanisms of residues on enzyme catalytic activity. In this study, molecular dynamics simulations and immobilized enzyme catalysis experiments were employed to investigate the structural dynamics and catalytic activity of QU10-FTase. The effects of structure and activity regulation of QU10-FTase induced by different environments, including the immobilized Fe3O4 interface and solvent temperatures, were investigated. The results show that the catalytic activity of QU10-FTase is suppressed by the immobilized Fe3O4. The all-atom MD simulations revealed that the binding sites of QU10-FTase to the Fe3O4 interface are far away from the catalytic triad, but the structures of the catalytic sites are influenced by the interface binding via an allosteric mechanism. The relationship between the structure and catalytic activity of QU10-FTase under different temperatures further demonstrated the allosteric regulation in the FTase. Our results not only demonstrate the possibility of improving the enzyme activity of QU10-FTase to produce FOS but also provide new insights into the allosteric mechanisms of fructosyltransferase.

This study systematically optimized the fermentation process for fructosyltransferase (FTase) production by Aspergillus niger FS054, integrating traditional experimental designs with machine learning approaches. Single–factor experiments initially identified critical medium components (carbon source, nitrogen sources, phosphate, and metal ions) and cultivation parameters (pH, liquid volume, inoculum size, temperature, and shaking speed). Subsequent Plackett–Burman screening identified sucrose, yeast extract paste, and NH_4Cl as the most influential medium factors. Through Box–Behnken response surface methodology (RSM), the optimal medium composition was determined as sucrose 156.65 g/L, yeast extract paste 42 g/L, and NH_4Cl 1.68 g/L, yielding an enzyme activity of 3249.00 ± 24.39 U/L (99.16 × 10^4 spores/mL, achieving a final enzyme activity of 3422.14 ± 36.86 U/L (1.1

Pulp breakdown is one of the primary symptoms of quality deterioration in postharvest longan fruit. As a pivotal pathogen, Phomopsis longanae Chi (P. P. longanae) ) leads to the spoilage of fresh longan. This work aimed to elucidate the influences of P. longanae infection on the metabolisms of energy and respiration in relation to longan pulp breakdown. Longan fruit were infected for 5 min with P. longanae at 10 (4) spores mL(-1 ), while the fruit dipped in distilled water were served as the control. These longans were stored for five days under the conditions of 28( degrees )C and 90 % relative humidity. The results showed that, compared with the control longans, P. longanae-- infected longans displayed a higher index of pulp breakdown, lower levels of ATP, ADP and EC, and lower activities of H+, Ca(2+ )and Mg2+-ATPase 2+-ATPase in the membranes of mitochondria, plasma and vacuoles. Besides, P. longanae-infected longans presented a higher respiration rate, higher activities of PGI, SDH, CCO, AAO, PPO and AOX, and higher levels of NAD and NADH, while showing lower activities of G-6-PDH + 6-PGDH and NADK, and lower levels of NADP and NADPH. These findings suggest that P. longanae infection aggravated the development of pulp breakdown in fresh longan, which was related to the reduced energy status and the enhanced respiratory metabolism.

To investigate the structure, diversity, and function of different paddy soil fungal communities and the factors affecting them in typical paddy cropping areas in China, five typical Chinese paddy soils were selected in this study, and the composition and diversity of soil fungal communities were comparatively analyzed using high-throughput sequencing technology and functionally predicted using the FUNGuild microecological tool. The results showed that： ① The fungal community diversity of soil samples from Heilongjiang （HLJ） was significantly lower than that of the other four regions （P<0.05）； the highest fungal community richness was found in paddy soils from Yunnan （YN）, which was significantly higher than that of the other regions （P<0.05）； and the soil samples from Hainan （HN）, Jiangxi （JX）, and Shandong （SD） were relatively close to each other. The highest average relative abundance at the level of the five typical paddy phyla was Ascomycota, and the genus with the highest average relative abundance was Tausonia. ② Fungi had the largest proportion of saprophytic trophic types, and their corresponding environmental functions were stronger. ③ The species abundance of soil fungi was highly significantly correlated with soil TP, EC, and BD （P<0.01）, and redundancy analyses also showed that soil TP was the main driver of the fungal community as well as the saprophytic functional taxa. The above results showed that the soil fungal community diversity and structure varied greatly among samples, and the relative abundance of fungal genera was affected by soil physical and chemical properties and altered the fungal community structure in paddy fields. The development of this study will provide theoretical references for the sustainable management based on fungal diversity and function of paddy fields.

IntroductionThe objective of this study is to examine the impact of various oyster shell soil conditioners, which are primarily composed of oyster shells, on the growth of tomatoes in acidic soil. Moreover, the aim of this investigation is to analyze the variety and structure of soil bacterial populations in close proximity to tomato roots while also contributing to the understanding of the physical, chemical, and biological mechanisms of oyster shell soil conditioners.MethodsTomato plants were grown in acidic red soil in three groups: a control group and a treatment group that used two types of oyster shell soil conditioners, OS (oyster shell powder) and OSF (oyster shell powder with organic microbial fertilizer). A range of soil physicochemical properties were measured to study differences in inter-soil physicochemical parameters and the growth of tomato plantings. In addition, this study utilized the CTAB (Cetyltrimethylammonium Bromide) technique to extract DNA from the soil in order to investigate the effects of oyster shell soil conditioner on the composition and diversity of bacterial populations. Utilizing high-throughput sequencing technologies and diversity index analysis, the composition and diversity of bacterial populations in the soil adjacent to plant roots were then evaluated. Ultimately, correlation analysis was used in this study to explore the relationship between environmental factors and the relative abundance of soil bacteria in the inter-root zone of tomato plants.ResultsThe findings indicated that the oyster shell soil conditioners were capable of modifying the physicochemical characteristics of the soil. This was evidenced by significant increases in soil total nitrogen (16.2 and 59.9%), soil total carbon (25.8 and 27.7%), pH (56.9 and 55.8%), and electrical conductivity (377.5 and 311.7%) in the OS and OSF groups, respectively, compared to the control group (p < 0.05). Additionally, data pertaining to tomato seed germination and seedling growth biomass demonstrated that both oyster shell soil conditioners facilitated the germination of tomato seeds and the growth of seedlings in an acidic red clay soil (p < 0.05). On the other hand, the application of two oyster shell soil conditioners resulted in a modest reduction in the diversity of inter-root soil bacteria in tomato plants. Specifically, the group treated with OSF exhibited the most substantial fall in the diversity index, which was 13.6% lower compared to the control group. The investigation carried out on the soil between tomato plant roots yielded findings about the identification of the ten most abundant phyla. These phyla together represented 91.00-97.64% of the overall abundance. In the inter-root soil of tomatoes, a study identified four major phyla, namely Proteobacteria, Bacteroidetes, Acidobacteria, and Actinobacteria, which collectively accounted for up to 85% of the total abundance. At the general level, the relative abundance of Massilia increased by 2.18 and 7.93%, Brevundimonas by 5.43 and 3.01%, and Lysobacter by 3.12 and 7.49% in the OS and OSF groups, respectively, compared to the control group. However, the pathogenic bacteria unidentified_Burkholderiaceae decreased by 5.76 and 5.05%, respectively. The correlation analysis yielded conclusive evidence indicating that, which involved the use of CCA (Canonical Correlation Analysis) graphs and Spearman correlation coefficients, pH exhibited a positive correlation (p < 0.05) with Shewanella and a negative correlation (p < 0.05) with Bradyrhizobium. The relative abundance of Lysobacter and Massilia exhibited a positive correlation with the levels of total soil nitrogen.DiscussionThe utilization of oyster shell soil conditioner on acidic red soil resulted in several positive effects. Firstly, it raised the pH level of the inter-root soil of tomato plants, which is typically acidic. This pH adjustment facilitated the germination of tomato seeds and promoted the growth of seedlings. In addition, the application of oyster shell soil conditioner resulted in changes in the structure of the bacterial community in the inter-root soil, leading to an increase in the relative abundance of Proteobacteria and Bacteroidetes and a decrease in the relative abundance of Acidobacteria. Furthermore, this treatment fostered the proliferation of genera of beneficial bacteria like Massilia, Brevundimonas, and Lysobacter, ultimately enhancing the fertility of the red soil.

Cell wall polysaccharides (CWP) are an important component of cell structure, and its content variation is a primary factor affecting the texture of fresh longan. The influences of dicyclohexylcarbodiimide (DCC) and disodium succinate (DS) treatments on the pulp softening and pulp breakdown, and their relation to CWP metabolism in pulp of longan fruit were explored. Compared with the control longan, DCC-treated fruit showed lower value of pulp firmness, higher index of pulp breakdown, higher expression levels of cell wall disassembly enzymes (CWDEs)-related genes (DlPME1, DlPME3, DlPG1, Dlfl-Gal1, Dlfl-Gal16, DlCx7, DlXET3, DlXET27), and higher activities of CWDEs including pectin methyl esterase (PME), polygalacturonase (PG), fl-galactosidase (fl-Gal), cellulase (Cx), xyloglucan endotransglycosylase (XET), lower values of cell wall materials, and lower levels of CWP including ionic-soluble pectin, covalent-soluble pectin, cellulose, and hemicellulose. Whereas, the opposite effects were exhibited in DS-treated fruit. The above data indicate that DCC-hastened longan pulp softening and pulp breakdown was due to the up-regulating expressions of CWDEs-related genes, the activating activities of CWDEs, and the accelerating CWP disassembly by DCC treatment. Whereas, DS repressed longan pulp softening and pulp breakdown through down-regulating the expressions of CWDEs-related genes, inhibiting CWDEs activities, and reducing CWP degradation.

Wetlands, which are ecosystems with the highest soil surface carbon density, have been severely degraded and replaced by artificial reclamation for fish and shrimp ponds in recent years. This transformation is causing intricate shifts in soil carbon pools and microbial stability. In this study, we examined natural wetlands and reclaimed aquaculture ponds in Southeast China to analyze the structure and network stability of soil microbial communities following the reclamation of estuarine wetlands and to elucidate the microbial-mediated mechanisms for regulating soil organic carbon (SOC). The aquaculture ponds presented significantly less average SOC content than the natural wetlands (p < 0.05). ACE, Chao1, and Shannon's indices of bacteria and fungi were decreased in aquaculture ponds. Less numbers of nodes and edge links in the co-occurrence network of soil fungi and bacteria in aquaculture ponds. This suggests reduced correlation and stability within the microbial network of aquaculture ponds. Decomposers in soil fungi (e.g. Dung Saprotroph) reduced. Reduced proportions of key phyla Ascomycota, Basidiomycota and Rozellomycota in the soil fungal network. Reduced proportions of key phyla Proteobacteria, Chloroflexi and Desulfobacterota in the soil bacterial network. In conclusion, our results suggest that converting wetland paddocks to intensive aquaculture ponds results in carbon pool loss and reduces soil microbial network stability. The results highlight the importance of protecting or moderately restoring mangrove wetlands along the coast of southeastern China. It is also predicted that such measures may enhance the storage capacity of soil carbon pools and improve the stability of carbon sequestration by soil microorganisms, thus offering a potential solution for mitigating global climate change.

The quantitative determination of major enzyme activities in postharvest fruit is a necessary biochemical experiment to investigate the physiological and metabolic mechanisms of fruit ripeness, senescence, and stress responses. However, it is necessary to choose appropriate methods to stably extract and determine target analytes from complex plant matrices due to the dynamic changes in enzyme activities of postharvest fruit during storage. Here, we outline sensitive and accurate methods for measuring fruit enzyme activities associated with key physiological processes including respiration, reactive oxygen species scavenging, membrane lipid degradation, energy synthesis, cell walls degradation, and disease resistance. This manuscript aims to provide guidance for future research in postharvest biology.

[目的] 铜藻为沿海常见的低质海藻,为实现铜藻高质利用,以新鲜铜藻为原料制备铜藻液体肥,研究其对上海青、黄瓜和番茄等3种蔬菜种子萌发和幼苗生长的影响,并基于偏最小二乘判别分析(Partial least squares discriminant analysis,PLS-DA)探究铜藻液体肥增肥的生物学效应.[方法] 采用酶法和发酵法2种工艺制备铜藻液体肥,并各设置5组稀释倍数(200倍、400倍、600倍、800倍和1000倍)进行种子萌发试验和幼苗盆栽试验.[结果] (1)种子萌发试验中,发酵法制备铜藻液体肥的200倍液、600倍液在上海青种子萌发上效果最佳,发芽指数较空白组显著提高11.8％,较两组阳性对照分别提高1.9％和1.3％;发酵制备的200倍液对黄瓜种子萌发影响最好,发芽指数较空白和两组阳性对照均显著提高,增幅分别达33.0％、21.0％和6.7％;发酵制备的1000倍液在番茄种子萌发上成效最佳,发芽指数较空白和两组阳性对照分别显著提升13.6％、14.4％和19.3％.(2)幼苗盆栽试验中,相关性分析结果表明各生长指标间普遍存在极显著正相关性,主成分分析(Principal component analysis, PCA)结果显示铜藻液体肥对3种蔬菜的影响作用各有差异,构建实验样品的PLS-DA模型分析不同制备方法的铜藻液体肥肥效并与阳性对照对比,结果表明发酵制备的400倍液对上海青幼苗促生效果最佳,各指标均显著高于阳性对照海藻肥,其中根鲜重提高最显著,增幅为144％;酶法制备的800倍液对黄瓜幼苗生长效果最好,各指标均显著高于阳性对照海藻肥,其中根长提高最显著,增幅为28％;发酵制备的600倍液对番茄幼苗作用效果最好,各指标均显著高于阳性对照海藻肥,其中株干重提高最显著,增幅为31％.[结论] 铜藻液体肥具备很好的增肥生物学效应,发酵法制备的铜藻液体肥肥效普遍优于酶法制备,施用前者能提高种子萌发率,促进幼苗地上部分和地下部分的生长,以上结果为海藻液体肥的生产与应用提供科学数据.

The viability of both China’s offshore fishing operations and the global marine fishing industry is threatened by the occurrence of red tides caused by Gymnodinium catenatum and Karenia mikimotoi. Effective control of these dinoflagellate-mediated red tides has become a pressing issue that requires immediate attention. In this study, High-efficiency marine alginolytic bacteria were isolated and underwent molecular biological identification to confirm their algicidal properties. Based on a combination of morphological, physiological, biochemical, and sequencing results, Strain Ps3 was identified as belonging to the species Pseudomonas sp. We examine the effects of algicidal bacteria on the red tide species G. catenatum and K. mikimotoi within an indoor experimental setting. Then gas chromatography– mass spectrometry (GC–MS) was used to analyze the structure of the algolytic active substances. This investigation demonstrated that with exposure to the algae-lysis experiment, the Ps3 strain has the best algae-lysis effect, with G. catenatum and K. mikimotoi reaching 83.0 and 78.3%. Our results from the sterile fermentation broth experiment showed that the inhibitory effect on the two red tide algae was positively correlated with the concentration of the treatment. At a treatment concentration of 2.0% (v/v), the 48 h lysis rates of G. catenatum and K. mikimotoi due to exposure to the Ps3 bacterial fermentation broth were 95.2 and 86.7%, respectively. The results of this study suggest that the algaecide may be a rapid and effective method to control dinoflagellate blooms, as evidenced by the observed changes in cellular morphology in all cases. In the ethyl acetate phase of Ps3 fermentation broth, the cyclic (leucine-leucine) dipeptide was the most abundant. The findings of this study contribute to our understanding of red tide prevention and control and provide a theoretical foundation for further research in this field.

食品工业上果糖基转移酶(FTase)是以蔗糖为底物酶法生产低聚果糖(FOS)的重要酶种,真菌是FTase主要微生物来源.以蔗糖为唯一碳源,通过检测发酵液FOS含量(初筛)和胞外、胞内的FTase酶活水平(复筛),成功筛选获得1株高产FTase的真菌菌株FS054,经ITS分子鉴定该菌株为黑曲霉,24 h胞内酶活达558.3 U/g.该FTase酶学特性研究表明:最适反应温度为55℃,最适反应pH为5.5,在30～35℃和pH 4.0～5.5的范围内酶活稳定性良好,0.5 mmol/L的Fe3+和Al3+具有激活效应,酶活性分别提高121.59％和110.26％,而Cu2+则严重抑制酶活力,相对酶活降至37.74％.本研究为后续全细胞生物合成FOS提供新酶源及前期基础.

Wetland ecosystems have dual functions as both carbon (C) sources and C sinks, playing a vital role in the world's C budget. Wetlands are prone to suffer from plant invasions, and for example, Spartina alternilora, a well-known invasive species, has rapidly expanded in coastal areas of Asia since 1979 and altered the C cycles in coastal wetland ecosystems. Fe(III) oxides are critical in the OC storage by formation of Fe-bound organic carbon (Fe-OC). But the impact of the invasion by S. alternilora in coastal wetlands on the formation and stabilization of Fe-OC is poorly known. Herein, we assessed soil Fe species contents, Fe-OC pool, and the microbial communities associated with these processes in seven wetlands dominated by both native (Kandelia obovate, Avicennia marina and Phragmites australis) and invasive (S. alternilora) plants. Our results showed that organical complexed Fe (Fep) concentration and Fe complexing index under S. alternilora community were lower than that under native communities. Soil Fe-OC concentration and molar OC:Fe ratio decreased (35.9% and 29.3%, respectively) after S. alternilora invasion in coastal wetlands, while the abundance of FeRB increased by 78.6%. The invasion of S. alternilora increased soil water content while decreased bulk density, and these changes could have important effects on Fe species and FeRB abundance. Moreover, Fe-OC was positive correlated with soil organic carbon (SOC), Fep, and Fe(III), indicating that SOC and Fe(III) concentrations directly affect the formation of Fe-OC. FeRB reacted on the combination of Fe (hydr-) oxides and SOC to indirectly affect Fe-OC through dissimila-tory Fe reduction, which further determined the stabilization and mineralization of SOC. Taken together, the invasion of S. alternilora hindered the generation and accumulation of soil Fe-OC pool weakening the stabili-zation of SOC in coastal wetlands. Therefore, the conservation and restoration of mangroves and other coastal wetlands provide a promising strategy for SOC sequestration and climate change mitigation.

果糖基转移酶是酶法生产低聚果糖的关键催化剂,固定化酶具有催化特性稳定、重复使用及节省用酶成本的优势,开展固定化果糖基转移酶催化特性的研究对其工业化应用提供数据依据.以海藻酸钠为载体,采用包埋法固定化果糖基转移酶,探究其最适催化温度、热稳定性,最适反应pH及pH稳定性、酶催化动力学等催化特性,并对固定化果糖基转移酶催化合成低聚果糖的应用进行初步研究.结果表明:海藻酸钠包埋法固定化果糖基转移酶的最适催化温度为50℃,pH值为5.0,酶学动力学米氏常数Km值为0.03 mg、mL-1,采用该固定化酶以蔗糖为底物可制得48.03％纯度的低聚果糖.海藻酸钠固定化果糖基转移酶相对游离酶具备更好的与蔗糖底物的亲和性、更佳的温度与pH稳定性,具备更好的工业应用潜力.