Isolation Of The Dominant Microflora And Dynamic Change Of Microbial Community During The Straw Decomposition In Soil

Agricultural waste as.a kind of potential biomass resource is difficult to be decomposed in nature.The microbes with a wide range of lignocellulose enzymes play an important role in the process of straw degradation.Lignocellulose enzymes are widely used to decompose biomass,bacaused of the lower energy consumption and higher conversation efficiency in degradation.Therefore,revealing changes of the functional microbial and structure can verify the regularity of the the straw degradation in soil,which will improve to screen the dominant microflora.This study uses the microbial pure culture method to achieve the enrichment and separation of the bacteria and fungi when at rice straw was bured into the soil located at different sites of Nanjing area(Jiangning.,Bauguazhou and Zijinshan).Straw samples were collected at different.time(after landfill 2 weeks,6 weeks,4 weeks,8 weeks,12 weeks,16 weeks)during the degradation of rice straw.The successional changes of the culturable microbial community and the dominant strain during the degradation process were studied using the microbial culture and identity technologies.The results were obtained as follows:A total of 576 bacteria and 43.2 fungi were isolated during the straw degradation in different locations.There are 576 species bacteria belong to 34 genera or species identitied by the molecular method,including Actinobacteria branch(1 species):Arthrobacter arilaitensis;Bacteroidete branch(2 species):Riemerella anatipestifer and Myroides odoratimimus,Firmicutes(12 species)including bacillus and staphylococcus;Proteobac.teria branch(19 species),including mainly pseudomonas genus,acinetobacter etc.A total of 432 strains of fungi belong to 17genera or species were isolated,including Zygomycota branch(3 species):Rhizopus sp.,Rhizopus oryzae and Lichtheimia ramose:The rest of the fungi were belong to the branch of Ascomycota(14 species)including aspergillus and penicillium genus,fusarium ssp.etc.The feature of microbial communities at different phase in different locations shows several patterns.Bacillus sp.dominated the bacterical community during the whole process of the straw degradation,especially the Bacillus pumius and the Bacillus amyloliquefaciens.While among the fungi including Aspergillus niger,Aspergillus flavus and Aspergillus fumigatus showed a large numerical advantage.The composition of the species maintains a reciprocal process,which has the characteristic of the emergence of new species and the disappearence of some species at the same time,while the dominant species was maintained during the whole degradation process.Contrastly,some species adapting their environment shows large deviation.The microbial species isolated from one region account for more than half(61.8%)in bacterial species diversity and 64.7%in fungi species diversity.The result of lignocellulosic enzyme-producing and the capability of degrade the rice straw shows that the strains isolated in the mid-to late phase have a higher enzyme activity in general.For example,the bacteriaLy sinibacillus sphaericus with a higher FPAse was isolated in the second stage of Jiangning area,two and three stage of Baguazhou area.Providencia sneebia was isolated in the fifth stage of rice straw degradation in Baguazhou and Zijinshan area.Among the fungi especially Penicillium with the best capability of degradation was enriched in the mid-to late stage of Jiangning area and middle stage of Baguazhou area.For the dominant strains such as bacillus and aspergillus,they are not able to produce the enzymes efficiently,as to the few strains with the lower capability of producing-enzyme at one stage in only one'location generally.It is conformed that the general rules of enrichment the microbial community appear during the degradation of rice straw.Four strains with the high enzyme activities were selected to construct microflora at different richness levels for studying their ability in rice straw degradation.-The results demonstrated that the microbial communities with higher species richness have higher lignocellulose enzymes activity,and thus improved the efficiency and the stability of the rice straw degradation.After 8 days of liquid fermentation and degradation of straw,the relative degradation rate of 4-strain microflora was 31.4%.