Effects Of Fungal Chitin On Soil Biochemical Properties

Chitin is an alkaline homopolysaccharide rich in carbon and nitrogen,it can be decomposed and utilized by microorganism in soil.A large number of research reports show that chitin can improve the soil,control diseases and improve the quality of crops.In this study,it was found that filamentous fungi could use potato to grow rapidly,its chitin yield after optimization accounts for about 25%of biomass.Make it possible to obtain a large quantity,stable and cheap chitin.In this experiment,a new chitin production technology was developed by using microbial fermentation method,in which the inedible cull potato discarded by vendors was recycled to make fungus fermentation medium,and Rhizopus oryzae preserved in the laboratory was used as the fermentation strain.The chitin production rate was over 27%.Taking the chitin produced in the laboratory as the raw material,combined with spectrophotometry and real-time fluorescence quantitative PCR technology,the soil experiment lasted for 122 days.By recording the data changes of pH value,total DNA concentration,concentration of related pathogens and chitinase activity and other dependent variables in the soil,the specific effects of chitin addition on the physical and chemical properties and bacterial colonies in the soil were analyzed.The main results are as follows:(1)Chitin was prepared by microbial fermentation.Taking advantage of the characteristics that filamentous fungi can propagate in large numbers through potatoes,we collected the cull potato which can't be eaten by people and abandoned by merchants and farmers for reuse,and made fermentation medium.Taking the laboratory preserved Rhizopus oryzae as the strain,we carried out microbial fermentation to produce chitin.The chitin content obtained by this method can reach 27.2%of the total biomass content,which is an efficient,green and environmental protection chitin production method.After optimization of the process,it is worthy of promotion and scale-up production.(2)Establishment of quantitative PCR model for pathogenic bacteria.The total DNA containing pathogenic bacteria was extracted from the sample soil by the method of extracting DNA from the kit.The target gene fragment was amplified by the general PCR amplification technology with the specific primers synthesized.The amplified product was made into plasmid by the DNA purification and recovery technology,and then sequenced and compared to confirm the homology of the target fragment.After the sequenced and compared,the obtained plasmid gradient was diluted into real ti The real-time fluorescence quantitative analysis software of rotor gene 6000 can automatically draw the standard curve,and finally achieve the goal of establishing the real-time Q-PCR monitoring model of pathogenic bacteria.(3)Chitin soil experiment.Streptomyces scab is the main pathogen of potato rhizome disease in soil,and TRPB is determined by comparing gene sequence DNA sequence has specificity,so as to determine the target gene fragment of the experiment in this chapter.Using the fungal chitin obtained by microbial fermentation method and the chitin products purchased in the market as the control group,122 days of soil experiment were carried out,and the results were sampled and analyzed at 0,9,21,30,48,60,75,91 and 122 days respectively.The changes of pH,total DNA content,chitinase activity and pathogen concentration in the soil after adding chitin samples of different species and concentrations were analyzed.Comprehensive analysis of the data showed that the amount of pathogenic bacteria decreased and the activity of chitinase increased while the total DNA increased after chitin reached a certain concentration was added into the soil for a period of time,which indicated that a large number of beneficial microorganisms were produced in the soil.Chitinase increased the activity of chitinase by increasing the number of chitinase,while chitinase could treat fungi in vitro to reduce the number of pathogenic bacteria In addition,chitin itself can destroy the cell wall structure of pathogenic bacteria to achieve the effect of inhibiting bacteria.It can be concluded that the addition of chitin can significantly change the composition and microflora of soil,effectively promote the growth of beneficial microorganisms,and inhibit the propagation of viral pathogens,so as to achieve the function of disease resistance.