Construction Of Rice Straw-degrading Microbial Flora And Exploration Of Its High-efficiency Degradation Mechanism

The effect of a single microorganism in degrading rice straw is not apparent.The microbial flora,combined with multiple microorganisms,can effectively degrade rice straw,which is currently the primary choice for straw waste degradation.To explore the interspecies coordination mechanism,the microbial flora can transform rice straw more efficiently than a single strain and provide a theoretical reference for improving the biodegradation process of straw materials.A microbial population combination with a degradation effect better than monoculture was constructed artificially through the combination of strains and the weight loss of rice straw as an indicator.The experimental strains were identified by molecular biology methods.Combining the growth rate of bacteria,pH value,ammonia nitrogen content,reducing sugar content,fermentation product and other indicators to obtain the interspecific coordination mechanism of the microbial population during the degradation of rice straw.And verify the experimental results.The research results are as follows:(1)Successfully screened 19 cellulolytic bacteria and three nitrogen-fixing bacteria.The cellulase activity of 19 cellulolytic bacteria was measured,and the ammonia nitrogen content of 3 nitrogen-fixing bacteria was measured.The experiment found that 19 cellulolytic bacteria have different cellulase activities.The three nitrogen-fixing bacteria can also fix nitrogen,increasing the ammonia nitrogen content in the medium.The strain B with the highest straw degradation efficiency was combined with 22 other strains to construct the best rice straw decomposing bacteria group B+D2+W1+G1.The bacteria group was cultured at 30? for eight days in a degradable medium.In 73.2%of rice straw,strain B's decomposing ability was increased by 22.4%compared with that of strain B alone.Under the optimal culture conditions:temperature 40?,initial pH 8.05,shaking speed 170 r/min,filling volume 102 mL,the bacterial colony can degrade 82.5%of rice straw after eight days of cultivation.(2)The strains B,D2,W1,and G1 in the rice straw decomposing bacteria group B+D2+W1+G1 were identified by molecular technology.The experiment found that strains B,D2,W1,and G1 were related species.They are B.cereus,B.amyloliquefaciens,O.intermedium,and B.licheniformis.Comparing the reducing sugar content,growth rate,ammonia nitrogen content,and pH value of the four combinations of B,B+D2,B+D2+W1,B+D2+W1+G1,and other physiological indicators.It was found that it was cultivated with a single strain.The three indexes of reducing sugar content,growth rate,and ammonia nitrogen content of the flora's mixed culture decreased step by step,and the pH value increased step by step.The analysis showed that reducing sugar content,growth rate,and ammonia nitrogen content may not be the reason for the increase in rice straw degradation rate,and acidic changes in the medium may cause the increase in straw degradation rate.(3)Strain B alone can reduce the amount of rice by 50.9%and produces a large amount of acid,phenol,and other substances.B+D2 co-cultivation resulted in a relative reduction of 87.4%of acids,and 61.9%of phenols in the fermentation broth(pentadecanoic acid,n-hexadecanoic acid,2,4 di-tert-butyl phenol,and 6-tert-butyl p-methyl)Phenol is significantly reduced),and the degradation rate of rice straw is 64.6%.When B+D2+W1 was co-cultured,the phenols during fermentation broth were further reduced by 15.7%(6-tert-butyl-p-cresol was significantly reduced)rice straw was degraded by 71.0%.When B+D2+W1+G1 was co-cultured,phenols continued to decrease by 10.7%,and rice straw was degraded by 73.3%.The experimental results showed that acids and phenols such as pentadecanoic acid,n-hexadecanoic acid,2,4-di-tert-butyl phenol,and 6-tert-butyl-p-cresol might inhibit the efficiency of strain B in decomposing rice straw.D2,W1,G1 may increase straw decomposition efficiency by reducing the acid and phenol content,including the above four substances.(4)Adding equal amounts of pentadecanoic acid,n-hexadecanoic acid,2,4-di-tert-butyl phenol,and 6-tert-butyl-p-cresol strain B is cultured alone will produce 1.66%and 17.53%,with their corresponding suppression effects 4.27%,3.35%,respectively.Experiments showed four chemicals,pentadecanoic acid,n-hexadecanoic acid,2,4 di-tert-butyl phenol,and 6-tert-butyl p-cresol,have inhibitory effects on the rice straw degradation efficiency of strain B.The medium was prepared with four chemicals,pentadecanoic acid,n-hexadecanoic acid,2,4-di-tert-butyl phenol 6-tert-butyl-p-cresol,as the sole carbon sources,and the strains D2,W1,G1 were cultivated and observed its metabolites.Experiments have shown that strains D2,W1,and G1 can decompose and utilize four substances,including pentadecanoic acid,n-hexadecanoic acid,2,4-di-tert-butyl phenol,and 6-tert-butyl-p-cresol.Acid and phenolic substances included.