Optimization of Enzymatic Extraction of Sodium Chondroitin Sulfate From Bovine Nasal Bone

Taking bovine nasal bone as a raw material,the sodium chondroitin sulfate was extracted by enzymolysis-ion adsorption-alcohol precipitation method,and the enzymolysis process was optimized.After single factor experiments,the response surface analysis was performed by software Design-Expert 8.0,and the optimal enzymolysis conditions were as follows:the trypsin concentration of 0.8%,the pH value of 9.0,the enzymolysis temperature at 52℃,and the enzymolysis time of 2.0 h.With this combination of conditions,the concentration of sodium chondroitin sulfate extract reached 11.3 g/L,the bovine nasal bone yield was 35%,and the finished product content was 92.5%,which provided guidance for industrial production.

Determination of Fosthiazate Residue in Ginger by Gas Chromatography

[Objectives] An analytical method was established for determining fosthiazate residue in ginger by gas chromatography with flame photometric detector(GC-NPD) to evaluate the safety of fosthiazate in ginger. [Methods] The fosthiazate residue in ginger was extracted with dichloromethane, and subjected to sodium chloride salt-out and liquid-liquid extraction with hexane and dichloromethane(the plant and soil samples had no need for the later two steps). The analysis was performed on gas chromatograph equipped with a flame photometric detector(GC-FPD), and the fosthiazate residue was quantitatively determined by calculating the peak area. [Results] The results of degradation dynamics showed that the half-life of fosthiazate was 7.2-8.7 d in ginger plants, and was 9.9-19.8 d in the soil. The results of the final residue test showed that after applying the fosthiazate granules according to the recommended high dose(active component 58.2 g a.i/m^2,WK) and low dose(38.8 g a.i/m^2,WK) once, the final residual amounts of fosthiazate in the ginger and soil were estimated to be <0.02 mg/kg and <0.02-0.103 mg/kg, respectively, while no fosthiazate residue was detected in all control samples(<0.02 mg/kg). The maximum residue limit(MRL) of fosthiazate in ginger was not established in China, and was 0.2 mg/kg in Japan. [Conclusions] The method was proved to meet the basic requirements of pesticide residue analysis on sensitivity, accuracy and precision and have good linearity. It is recommended that when using fosthiazate granules to control root-knot nematode and root rot in ginger, it is applied at the highest dose of 38.8 g ai/m^2,WK once 30 d before ginger cultivation to treat the soil, and ginger is harvested in the ginger harvest period.

Occurrence and Control of Weeds in Abandoned Fields in Central Hunan

[Objectives]This study was conducted to clarify the occurrence of weeds,and give relevant comprehensive control suggestions accordingly.[Methods]The species and community characteristics of weeds in abandoned rice fields in central Hunan were investigated and analyzed.[Results]There were 75 species of weeds in the abandoned farmland in central Hunan,belonging to 66 genera,27 families.Among them,22 species had a relative abundance of more than 5%.According to the different water environments of abandoned fields,there were differences in the types and structures of weeds.They succeeded to wetland vegetation types and dryland vegetation types respectively.Species grown in the original farmland still exist in abandoned fields,but they were mainly invaded by field weeds,such as Digitaria sanguinalis,Eleusine indica,Panicum acroanthum,Bidens pilosa,and Xanthium sibiricum.[Conclusions]This study lays a foundation for fully guaranteeing the actual results of re-cultivation of abandoned land in rural areas.

Study on Dormancy Mechanism and Dormancy-breaking Method of Velvetleaf(Abutilon theophrasti)Seeds

[Objectives]This study was conducted to explore how can we better break the dormancy of velvetleaf seeds and the best method to promote seed germination.[Methods]With the seeds of velvetleaf(Abutilon theophrasti)as experimental materials,the dormancy of velvetleaf seeds was revealed through seed vigor determination,water absorption rate determination and germination tests,and the seeds of velvetleaf were treated by physical and chemical methods to explore the best method for breaking dormancy of velvetleaf seeds.[Results]Poor water permeability of seed coat and endogenous inhibitory substances present in the seeds were the main reasons leading to the dormancy of velvetleaf seeds.The shell-breaking treatment,98%concentrated sulfuric acid treatment and 40%NaOH strong alkali treatment all could break the dormancy obstacle of velvetleaf seed coat.Compositing the above measures with 200 mg/ml gibberellin solution could further improve the germination ability of seeds.Among them,compositing the mechanical shell-breaking treatment with gibberellin had the best effect,followed by the composite of 10 and 15 min of 98%concentrated sulfuric acid treatment with gibberellin.[Conclusions]This study lays a foundation for the utilization and development and the comprehensive prevention and control research of velvetleaf seeds.

Research Progress of Application of Microbial Inoculants in Agricultural Production

Microbial inoculants have received increasing attention in strengthening plant biological barriers,antagonizing and inhibiting harmful microorganisms,and ensuring the safe production of agricultural products.This paper summarized the research status of agricultural microbial inoculants,the application of microbial inoculants in agriculture,and the trends and prospects of agricultural microbial research.

Analysis of the Choice of Return Mechanism of PPP Model in Rural Human Settlement Improvement under the Rural Revitalization Strat­egy:Research Based on the Perspective of Evolutionary Game

The improvement of rural human settlement environment is a significant direction of the rural revitalization strategy.Based on the finite rational evolutionary game theory,a cooperative behavior evolutionary game model of rural human settlement environment improvement PPP model with local government,social capital and rural residents as the main game players with the reward mechanism of Government Payment and one with the reward mechanism of Viability Gap Funding are constructed.Comparing the total project revenue of two reward mechanisms,the thesis will obtain the effects of choosing the reward mechanism of rural human settlement improvement PPP.Finally,available suggestions are made to the decision of the reward mechanism of PPP project about rural human settlement environment,thus promoting the application and development of PPP in rural environmental management and to promote sustainable improvement of rural habitat improvement.

Total synthesis and biological evaluation of dracaenins A and B

The first total synthesis of dracaenins A and B is achieved in four steps.The synthesis features the conver-gent coupling of three readily available fragments with minimized use of protecting groups.The chemical synthesis enables the discovery of their activity in stimulating platelet aggregation,and thus,sheds light on the possible origin of the hemostatic effect of dragon’s blood.