Analysis of the antimicrobial activity of Lactobacillus plantarum YM-4-3: implications of suitable conditions for extending the shelf life of fermented soybean products.

Lactobacillus (Lb.) plantarum is typically used as a starter culture in salt-fermented foods. Here we report 3-4% NaCl reducing the antimicrobial activity of Lb. plantarum strain YM-4-3, owing to the decrease of bacterial growth, plantaricin activity and expression levels of plantaricin biosynthesis-related genes (PBGs). Meanwhile, 1% NaCl promoted slightly the growth of YM-4-3 and up-regulated the expression of PBGs to the greatest level. The results from a spoilage experiment of fermented soybean products revealed that the 1% NaCl and YM-4-3 treatment group had the longest shelf life representing the minimum number of pathogenic bacteria and the lowest degree of mildew. Therefore, a combination of Lb. plantarum with a low concentration of salt, such as 1% NaCl, is a recommended condition for preparing fermented foods.

Transcriptomic analysis of de novo folate biosynthetic genes in Lactobacillus plantarum strain 4_3 in fermented soybean.

Folate is an important intermediate in cellular metabolism. However, because of a lack of key enzymes in the folate biosynthetic pathway, humans require supplementation with dietary folate. Some Lactobacillus plantarum strains have the ability to produce folate. To gain a better understanding of the folate biosynthetic pathway in the L. plantarum strain 4_3, which generates high folate yields, L. plantarum strain 4_3 was grown in folic acid casei medium (FACM) and fermented soybean, after obtaining a draft genome sequence. The pH values and folate yields were monitored during culturing, as were the transcriptomic profiles of cultured bacteria. The folate content increased for 12 h and then decreased before increasing again. All the genes involved in the de novo biosynthesis of folate were detected in both the genomic and transcriptomic data. The upregulation of the para-aminobenzoate biosynthesis pathway could explain the folate production in fermented soybean. Soybeans are a good substrate for the production of functional foods because of their well-suited cultivation and nutritional quality. The results of this study provide a good explanation for the high folate production observed during the fermentation of soybeans.

[Distribution Characteristics of Solute Nitrogen in the Water-Sediment of Farmland Drainage Ditch].

Along with the highlighted water environmental issues and the gradual effective renovation of the point source pollution (PSP) such as industrial waste, the agricultural non-point source pollution (AGNSP) caused by the non-scientific application of fertilizers and pesticides has attracted more and more attention. On the basis of strengthening the field "source control", making the best use of agricultural drainage ditch (pond) system "intercepting process" is a vital means of agriculture non-point source pollution control and management at the present stage. Ditch system is not only an important part of the farmland irrigation and drainage engineering, but also a vital corridor of AGNSP of solute transport. The unique farmland drainage ditch water-sediment-plant system in ecology and physics is similar to linear wetland function,and has effect of interception and purification on non-point source solute in farmland drainage. Non-point source solute transformation mechanism of each medium in the farmland drainage ditch water-sediment-plant system is unclear, in view of the current situation, the study took the natural channel as the object. Taking the non-point source solute nitrogen as an example, by field monitoring test during March 2014-February 2015, the distribution characteristics of non-point solute nitrogen in the water-sediment of the farmland drainage ditch were analyzed. The results indicated that the concentration of total nitrogen in water and the total nitrogen content in the sediment of the experimental ditches both showed a certain degree of decreasing trend along the longitudinal ditch, which represented a purification effect of the ditch system on the non-point source solute. The concentration of total nitrogen in water and the total nitrogen content in the sediment had big inhomogeneity in the ditch cross-sectional distribution, and its distribution characteristics were related to the shape of the cross-section, flow variation process, flow velocity distribution and other factors. The balance of the total nitrogen concentration was 76.89%, and the total nitrogen content in the sediment was 57.04%. During the trial period, the total nitrogen concentration in the water was "concave" shape, while in the sediment it was "convex" shape, showing opposite changing trends.

[Transformation of Non-point Source Soluble Nitrogen in Simulated Drainage Ditch].

The drainage ditch has a compound ecosystem structure consisting of water, sediment and plants. Migration and transformation of the non-point source solute is important to study interception, control and management of agricultural non-point source pollution in the drainage ditch. Based on the experiment on static simulation of drainage ditches, the article used typical non-point source soluble nitrogen as an example to analyze the changing process of nitrogen content in water, sediment and reeds, and to study the effects of the sediment adsorption and desorption, reeds growth and death in different periods on nitrogen concentration in water. The article discussed nitrogen migration in water-sediment-reeds compound ecosystem and its influence on nitrogen concentration in water. The results showed that both adsorption and desorption in sediment and absorption and assimilation of reeds growth had effect on nitrogen concentration in water. The effect before October was reducing the nitrogen concentration in water, which was the process of nitrogen purification in water. After October, the nitrogen concentration in water increased and made it easy to form secondary nitrogen pollution. Meanwhile, the migration in the water-sediment-seeds ecosystem in simulated drainage ditch had close ties, any migration and transformation of nitrogen in a single medium or between different mediums would cause adjustment of nitrogen concentration in water.

[Study on water quality monitoring scheme based on non-point source pollution].

In order to improve standardization and normalization of non-point source pollution monitoring, this paper summarized the non-point source pollution monitoring scheme that based on conventional technology condition. The scheme firstly emphasized the preparation work before monitoring, including situation investigation and index selection of the monitoring area and so on; In the process of establishing monitoring scheme, the monitoring area was divided into three types: city, agriculture and watershed. Take urban area monitoring scheme for Xi'an as an example, through dividing function zone setting sampling point, summarized sampling time interval, frequency and sampling methods during a rainfall process. An irrigation district was an example for agricultural monitoring scheme, through unit division, setting sampling point at the approach channel and drain channel, introduced sampling times, interval time and so on in the process of irrigation. Watershed monitoring scheme's example was the Weihe GuanZhong section, raised the setting principle of each sample section, and analyzed each section's sampling law in the process of rainfall. Finally the principal character of different non-point source pollution monitoring areas was discussed, and concluded that non-point source pollution monitoring scheme is the base of non-point source pollution study and control.

[Simulation and application of the agricultural non-point source pollutants in drainage ditch].

Drainage ditch system is the transitional zone between yield in the field and receiving waters for agricultural non-point source pollutants. Based on the brief analysis of the migration and transformation process of agricultural non-point source pollutants in drainage ditch system, the one-dimensional transport model of agricultural non-point source pollutants in drainage ditch system was constructed on the basis of the equation of continuity of flow and pollutants migration transform. Taking the Di Yi drainage ditch system, in the Qing-Tong-Xia irrigation district at the Yellow River upstream, as an example, combining with actual situation, the drainage discharge and concentration of nitrate nitrogen and total phosphorus were simulated by this model. The results show that the simulated drainage discharge accords with measured data approximately and Nash-Suttcliffe coefficient is 0.82, the simulated concentration of nitrate nitrogen and total phosphorus in farmland drainage was reasonable.

[Experimental research on migration characteristics of nitrogen and phosphorus in Qingtongxia irrigation district].

Taking the Qingtongxia irrigation district at the Yellow River upstream as an example, based on the monitor experiment material, this paper has analyzed the migration characteristics of nitrogen and phosphorus in the water conveyance system, the field system and the drainage system in the irrigations district. The results showed that, the concentrations of nitrogen and phosphorus showed increasing tendency in the water conveyance system and the increasing extent related to the channel substrate and content of nitrogen and phosphorus. In the field system, the fertilizer application process has a great influence on the concentration of nitrogen and phosphorus in farmland irrigation drainage and soil. During the crop growing period, nitrogen content in the soil above 60 cm changes greatly, total phosphorus content in the soil changes slightly correspondingly. In the drainage system, the concentrations of nitrogen and phosphorus showed decreasing tendency, from the end of farm ditch to outlet of agricultural drain, the concentration of ammonia nitrogen, nitrate nitrogen and total phosphorus in the agricultural drain decreased by 25%, 41% and 45% respectively. Affected by livestock and poultry breeding pollution and so on, the concentration of nitrogen showed increasing tendency in mainstay drainage ditch.

[Establishment and application of the estimation model for agricultural non-point source pollution in the field].

The quantitative research on pollution loads is the basis of control, evaluation and management of non-point source pollution. The estimation of agricultural non-point source pollution loads includes two steps: evaluation of water discharge and prediction of pollutant concentration in agricultural drain. Water discharge was calculated by DRAINMOD model based on the principle of water balance on farmland. Meanwhile, the synthesis of fertilization and irrigation is used as an impulse input to the farmland, the pollutant concentration changes in agricultural drain is looked as the response process corresponding to the impulse input, the complex migratory and transforming process of pollutant in soil are expressed implied by Inverse Gaussian Probability Density Function. Based on the above, the estimation model of agricultural non-point source pollution loads at field scale was constructed. Taking the typical experimentation area of Qingtongxia Irrigation District in Ningxia as an example, the loads of nitrate nitrogen and total phosphorus in paddy-field drain was simulated by this model. The results show that the simulated accorded with measured data approximately and Nash-Suttcliffe coefficient is 0.963 and 0.945 respectively.