Advances in regulating vitamin K2 production through metabolic engineering strategies.

Vitamin K2 (menaquinone, VK2, MK) is an essential lipid-soluble vitamin that plays critical roles in inhibiting cell ferroptosis, improving blood clotting, and preventing osteoporosis. The increased global demand for VK2 has inspired interest in novel production strategies. In this review, various novel metabolic regulation strategies, including static and dynamic metabolic regulation, are summarized and discussed. Furthermore, the advantages and disadvantages of both strategies are analyzed in-depth to highlight the bottlenecks facing microbial VK2 production on an industrial scale. Finally, advanced metabolic engineering biotechnology for future microbial VK2 production will also be discussed. In summary, this review provides in-depth information and offers an outlook on metabolic engineering strategies for VK2 production.

Enhanced vitamin K2 production by engineered Bacillus subtilis during leakage fermentation.

Menaquinone-7 (MK-7), a valuable member of the vitamin K2 series, is an essential nutrient for humans. It is used for treating coagulation disorders, and osteoporosis, promoting liver function recovery, and preventing cardiovascular diseases. In this study, to further improve the metabolic synthesis of MK-7 by the mutant strain, the effect of surfactants on the metabolic synthesis of MK-7 by the mutant strain Bacillus subtilis 168 KO-SinR (BS168 KO-SinR) was analyzed. The scanning electron microscopy and flow cytometry results showed that the addition of surfactants changed the permeability of the cell membrane of the mutant strain and the structural components of the biofilm. When 0.7% Tween-80 was added into the medium, the extracellular and intracellular synthesis of MK-7 reached 28.8 mg/L and 59.2 mg/L, respectively, increasing the total synthesis of MK-7 by 80.3%. Quantitative real-time PCR showed that the addition of surfactant significantly increased the expression level of MK-7 synthesis-related genes, and the electron microscopy results showed that the addition of surfactant changed the permeability of the cell membrane. The research results of this paper can serve as a reference for the industrial development of MK-7 prepared by fermentation.

Experimental study of interception effect by submerged dam on microplastics.

Submerged dam can alter microplastic (MP) transport, and act as a sink for MPs. In this paper, we investigated the interception rates of Polyvinyl chloride (PVC) and Polystyrene (PS) by an artificial submerged dam in a flow flume at first, and found that most of the un-intercepted PVC and PS particles by the dam accumulated behind it under the subcritical (Fr < 1) and turbulent (Re > 500) flows. PVC particles behind the dam mainly concentrated within two dam widths, and the concentration of PS particles decreased with the distance behind the dam lengthening. Then, we performed linear regression fitting and Redundancy Analysis (RDA) between the interception rates collected in 162 experiment tests and environmental factors, including flow velocity, distance to dam and MP concentration. The results showed that the interception rate of PVC and PS particles increased with the distance to dam lengthening, but decreased with the flow velocity and MP concentration heightening. RDA revealed that the interception rate was influenced by flow velocity, distance to dam, and MP concentration from the most to the least. Our findings are believed to contribute to understanding the mechanism of the interception effect of submerged dam on microplastics.

[Change and Prediction of Water Purification Function in the South Bank of Hangzhou Bay in the Past 20 Years].

The investigation of regional water purification functionality and its influencing factors holds significant pragmatic implications in understanding the potential of regional water purification, guiding context-specific regional comprehensive planning schemes, and environmental conservation measures. The study site, situated along the southern coast of Hangzhou Bay, represents a prototypical region characterized by intricate land-sea interactions that bear substantial economic and ecological functions. By assimilating a meticulously collected topographical and land-use dataset, in conjunction with site-specific meteorological records, the water purification model embedded within the integrated valuation of ecosystem services and trade-offs (InVEST) framework was employed to scrutinize the spatiotemporal dynamics of nitrogen (N) and phosphorus (P) loads, discharges, and removals within the southern coast of Hangzhou Bay. The prime objective of this study was to unravel the differentials in water purification functionality under diverse developmental scenarios. The investigation unearthed distinct temporal discrepancies in N and P discharges and removals over two temporal dimensions. Relative to the benchmark year 2000, the total N load experienced a reduction of 276.72 t, whereas the N discharge and removals decreased by 140.86 and 137.86 t, respectively, in the year 2020. In contrast, the total P load observed an increase of 93.65 t, accompanied by a surge in P discharge and removals by 28.91 and 64.74 t, respectively. Spatially, the distribution pattern of N and P discharges exhibited a general inclination of elevated values in the northern region and subdued values in the southern region, with certain pockets in the southern region exhibiting pronounced peaks, intimately associated with land-use typologies. Simulation analyses conducted under distinct scenarios unveiled that under the natural development priority scenario, the N and P discharges within the study area amounted to 1 682.36 and 115.50 t, respectively. Conversely, under the scenario emphasizing economic development, the regional N and P discharges showed an approximate escalation of 83.02% and 79.93%, correspondingly. In contrast, under the scenario emphasizing environmental conservation, the regional N and P discharges exhibited a notable decline of approximately 79.96% and 56.44%, respectively. Hence, the scenario prioritizing the amalgamation of environmental conservation and development effectively reduced the N and P discharges within the region, bolstering the water purification functionality. The results derived from this study furnish a solid theoretical foundation for effectuating region-specific planning schemes fostering coordinated economic and ecological advancement within the study area.

Biogeographic effects shape soil bacterial communities across intertidal zones on island beaches through regulating soil properties.

Island coastal zones are often mistakenly perceived as "ecological desert". Actually, they harbour unique communities of organisms. The biodiversity on islands is primarily influenced by the effects of area and isolation (distance from the mainland), which mainly focused on plants and animals, encompassing studies of entire islands. However, the application of area and isolation effects to soil microorganisms on island beaches across the intertidal zones remains largely unexplored. We hypothesized that island area and isolation shape soil bacterial communities by regulating soil properties on island beaches, due to the fact that local soil properties might be strongly influenced by land-use, which may vary among islands of different sizes and isolations. To test this hypothesis, we conducted a study on 108 plots spanning 4 intertidal zones on 9 representative island beaches within Zhoushan Archipelago, eastern China. We employed one-way ANOVA and Tukey's honestly significant difference (HSD) test to assess the differences in diversity, composition of soil bacterial communities and soil properties among intertidal zones. Redundancy analysis and structural equation modelling (SEM) were used to examine the direct and indirect impacts of beach area and isolation on soil bacterial communities. Our findings revealed that the area and isolation did not significantly influence soil bacterial diversity and the relative abundance of dominant soil bacterial phyla. However, soil nitrogen (soil N), phosphorus (soil P), organic carbon (SOC), available potassium content (soil AK), and electrical conductivity (soil EC) showed significant increases with the area and isolation. As the tidal gradient increased on beaches, soil bacterial OTU richness, Chao 1, and relative abundance of Planctomycetota and Crenarchaeota decreased, while relative abundance of other soil bacterial phyla increased. We found that influences of island area and isolation shape soil bacterial communities on beaches by regulating soil properties, particularly soil moisture, salinity, and nutrients, all of which are also influenced by area and isolation. Island with larger areas and in lower intertidal zones, characterized by higher soil water content (SWC), soil EC, and soil AK, exhibited greater soil bacterial diversity and fewer dominant soil bacterial phyla. Conversely, in the higher intertidal zones with vegetation containing higher soil N and SOC, lower soil bacterial diversity and more dominant soil bacterial phyla were observed. These findings have the potential to enhance our new understanding of how island biogeography in interpreting island biome patterns.

Poly-γ-Glutamic Acid Production by Engineering a DegU Quorum-Sensing Circuit in Bacillus subtilis.

As a natural biological macromolecule, γ-polyglutamic acid (γ-PGA) plays a significant role in medicine, food, and cosmetic industries owing to its unique properties of biocompatibility, biodegradability, water solubility, and viscosity. Although many strategies have been adopted to increase the yield of γ-PGA in Bacillus subtilis, the effectiveness of these common approaches is not high because the strong viscosity affects cell growth. However, dynamic regulation based on quorum sensing (QS) has been extensively applied as a fundamental tool for fine-tuning gene expression in reaction to changes in cell density without adding expensive inducers. A modular PhrQ-RapQ-DegU QS system is developed based on promoter PD4, which is upregulated by phosphorylated DegU (DegU-P). In this study, first, we analyzed the DegU-based gene expression regulation system in B. subtilis 168. We constructed a promoter library of different abilities, selected suitable promoters from the library, and performed mutation screening on the selected promoters and degU region. Furthermore, we constructed a PhrQ-RapQ-DegU QS system to dynamically control the synthesis of γ-PGA in BS168. Cell growth and efficient synthesis of the target product can be dynamically balanced by the QS system. Our dynamic adjustment approach increased the yield of γ-PGA to 6.53-fold of that by static regulation in a 3 L bioreactor, which verified the effectiveness of this strategy. In summary, the PhrQ-RapQ-DegU QS system has been successfully integrated with biocatalytic functions to achieve dynamic metabolic pathway control in BS168, which can be stretched to a large number of microorganisms to fine-tune gene expression and enhance the production of metabolites.

[Monitoring leaf nitrogen concentration and nitrogen accumulation of double cropping rice based on crop growth monitoring and diagnosis apparatus]. / 基于作物生长监测诊断仪的双季稻叶片氮含量和氮积累量监测.

To verify the accuracy and adaptability of crop growth monitoring and diagnosis apparatus (CGMD) in monitoring nitrogen nutrition index of double cropping rice, we established a monitoring model of leaf nitrogen concentration (LNC) and leaf nitrogen accumulation (LNA) for double cropping rice based on CGMD. Eight early and late rice cultivars were selected and four nitrogen application rates were set up. The differential vegetation index (DVI), normalized difference vegetation index (NDVI) and ratio vegetation index (RVI) were collected using CGMD. Meanwhile, ASD FH2 high spectrometer was used to collect canopy spectral reflectance and calculated DVI, NDVI, and RVI. To verify the accuracy of CGMD, we compared the canopy vegetation indices change characteristics collected by CGMD and ASD FH2. The CGMD-based monitoring models of LNC and LNA were established, which was tested with independent field data. The results showed that LNC, LNA, DVI, NDVI and RVI of early and late rice increased with increasing nitrogen application rate, and increased first and then decreased with the advance of growth progress. The determination coefficient (R2) of fitting for DVI, NDVI and RVI from CGMD and ASD FH2 were 0.9350, 0.9436 and 0.9433, respectively. This result indicated that the measurement accuracy of CGMD was high, and that the CGMD could be used to replace ASD FH2 to measure canopy vegetation indices of early and late rice. Compared with the three canopy vegetation indices based on CGMD, the correlation between NDVICGMD and LNC and that between RVICGMD and LNA was the highest. The exponential model based on NDVICGMD could be used to accurate estimate LNC with the R2 in the range of 0.8581-0.9318, and the root mean square error (RMSE), relation root mean square error (RRMSE) and correlation coefficient (r) of model validation in the range of 0.1%-0.2%, 4.0%-8.5%, and 0.9041-0.9854, respectively. The power function model based on RVICGMD could be used to estimate LNA with the R2 in the range of 0.8684-0.9577, and the RMSE, RRMSE and r of model validation in the range of 0.37-0.89 g·m-2, 6.7%-20.4% and 0.9191-0.9851, respectively. Compared with the chemical testing method, using the CGMD could conveniently and accurately measure LNC and LNA of early and late rice, which had a potential to be widely applied for high yield and high efficiency cultivation and precise management of nitrogen fertilizer in double cropping rice production.

[Model construction and application for nitrogen nutrition monitoring and diagnosis in double-cropping rice of Jiangxi Province, China]. / æ±Ÿè¥¿åŒå­£ç¨»æ°®ç´ ç›‘æµ‹è¯Šæ–­æ¨¡åž‹çš„å»ºç«‹ä¸Žåº”ç”¨.

The spectrometer-based nitrogen (N) nutrition monitoring and diagnosis models for double-cropping rice in Jiangxi is important for recommending precise N topdressing rate, achieving high yield, improving grain quality and increasing economic efficiency. Field experiments were conducted in Jiangxi in 2016 and 2017, involving different early rice and late rice cultivars and N application rates. Plant N accumulation (PNA) and canopy spectral vegetation indices (VIs) were measured at tillering and jointing stages with two spectrometers, i.e., GreenSeeker (an active multispectral sensor containing 780 and 660 nm wavelengths) and crop growth monitoring and diagnosis apparatus (CGMD, a passive multispectral sensor containing 810 and 720 nm wavelengths). The VI-based models of PNA were established from a experimental dataset and then validated using an independent dataset. The N topdressing rates for tillering and jointing stages were calculated using the newly developed N spectral diagnosis model and higher yield cultivation experience of double-cropping rice. The results showed that the VIs from two spectrometers were strongly positively correlated with PNA at both growth stages, with the model performance for tillering or jointing stages was better than that for the early growth stages. The exponential equation of normalized difference vegetation index (NDVI(780,660)) from GreenSeeker could be used to estimate PNA with a determination coefficient (R2) in the range of 0.92-0.94, the root mean square error (RMSE), relative root mean square error (RRMSE) and correlation coefficient (r) of model validation in the range of 3.09-5.96 kg·hm-2, 5.8%-18.5% and 0.92-0.98, respectively. The linear equation of difference vegetation index (DVI(810,720)) from CGMD could be used to estimate PNA with a R2 in the range of 0.90-0.93, the RMSE, RRMSE and r of model validation in the range of 3.71-6.33 kg·hm-2, 11.7%-14.3% and 0.93-0.96, respectively. The recommended N topdressing rate with CGMD was higher than that with GreenSeeker. Compared with conventional farmer's plan, the precision N application plan reduced N fertilizer application rate by 5.5 kg·hm-2, while N agronomic efficiency and net income was improved by 0.8% and 128 yuan·hm-2, respectively. Application of the spectral monitoring and diagnosis method to guiding fertilization could reduce cost and increase grain yield and net income, and thus had great potential for guiding double-cropping rice production.