Dynamic Analysis And Efficient Strain Screening Of Straw Degrading Bacteria In Rice And Wheat Rotation System

Straw spoilage agent is the most convenient and effective way to degrade straw at present,and the key of compounding straw spoilage agent is to select the strain with high efficiency straw degradation ability.At present,it has been reported that many straw degrading bacteria have been screened,but not many strains have been screened in the rice-wheat rotation system along the Huaihe region,and the screened strains are single without analysis combined with the bacterial community dynamics.Based on the analysis of the browns soil and returning tide soil the change law of quality and chemical composition of straw,straw degradation bacteria community structure on the basis of dynamic,first through selective tablet quantitative screening method of combining the advantage and the enzyme activity and efficient cellulose and lignin degradation bacterium and to identify the species,the best fermentation conditions of the selected strain to do the system research.The main results are as follows:1.Under different soil treatments,the straw decomposition rate was fast in the early stage and slow in the later stage.The total decomposition rate of straw in different soil types did not differ greatly,but the speed of decomposition process was slightly different.From 0-15d at the beginning of the experiment,the decomposition rate of wheat straw reached 17.46%in yellow brown soil and 24.19%in tidal soil.From 15 to 120 d,the decay rate decreased significantly,and the straw decay entered a slow period.By the end of decomposition 120 d,the total decomposition rate of straw under yellow brown soil and tidal soil treatment was 42.39%and 43.94%,respectively.The infrared spectral patterns of wheat straw in different soil and different decomposition periods were similar,but some main characteristic absorption peaks and their absorption intensity changed.At the 60th day of decomposition,the intensity of main characteristic absorption peak increased most obviously.At 120 d,the absorption peaks weakened slightly.Under tidal soil treatment,the relative strength of the absorption peak can be divided into two types:the relative strength of the absorption peak at 3440?3430 cm-1,1640-1630 cm-1 and 1460 cm-1 keeps increasing.The absorption peak intensity at 2925?2850 cm-1 and 1000?1100 cm-1 first increased and then decreased,reaching the maximum absorption intensity at 60 days,and then began to decline.2.In the process of straw decomposition,the abundance,diversity and dominant bacteria of the bacterial community increased obviously,and decreased in the late stage of straw decomposition,but it was still higher than that in the early stage.The Indexes of Chao 1 under yellow brown soil and tidal soil treatment reached the maximum at 60 d,respectively 1427.9 and 2788.9;Shannon index under yellow brown soil treatment reached the maximum at 60 d,respectively,at 8.55,and then decreased to 6.64.However,Shannon index under tidal soil treatment has been increasing,reaching a maximum of 8.61 at 120 d.With the extension of decomposition time,the number of dominant bacteria first increased and then decreased.In both soil treatments,the number of dominant bacteria reached the maximum at 60 d,which were 6 and 5,respectively.3.Through CMC-Na plate transparent ring test and aniline blue plate decolorize test,9 strains of cellulose bacteria and 7 strains of lignin bacteria were selected combine with the bacterial identification results.These 16 strains include 9 genera:Klebsiella,Chitinophaga,Bacillus,Spinobacter,Stenotrophomonas,Escherichia,Raoult,Enterobacter,pseudomonas.Further,through the comparison of cellulase and ligninase activity(lignin peroxidase,manganese peroxidase and laccase),one high-efficient cellulose and ligninase degrading strain was selected from the yellow-tan soil and the moisture soil respectively,namely X15C2,X15H2,M15H2 and M15C3.X15C2 and X15H2 showed higher cellulase activity,respectively 1603.04 g/min/g and 1575.09 g/min/g.The lignin peroxidase,manganese peroxidase and laccase of M15H2 and M15C3 were 125.49,23.91,8.91 and 103.14,22.35 and 22.36,respectively.4.Through shaking flask experiments with different carbon,nitrogen,pH and temperature of the 4 strains screened.It was found that the optimal fermentation and culture conditions of strains X15H2,M15H2 and M15C3 were all initial pH of 5 and 28?,and the optimal fermentation and culture conditions of strain X15C2 were initial pH of 6 and 36?.The best carbon and nitrogen sources of strain X15H2 were sucrose and yeast powder.The best carbon and nitrogen sources of strain X15C2 were sucrose and peptone respectively.The optimal carbon and nitrogen sources of strain M15H2 were sucrose and yeast powder.The best carbon and nitrogen sources of strain M15C3 were maltose and yeast powder.To sum up,with the extension of decomposition time,straw decomposition rate gradually increased,0-15 d decay rate increased the fastest,at the same time,the diversity,richness and dominant bacteria were significantly increased,and when the decay days were 15d,four strains with high efficiency of enzyme production were selected.