Isolation And Identification Of Thermophilic Bacterium Strains With High Degradation And The Effects On Dead Pig Composting

To explore the application of composting in dead pigs harmless treatment.primary screening was done by using diluted plate count and selective medium,and then enzyme activity was measured for secondary screening.The strains were identified by 16 SrDNA gene sequences and the culture conditions(temperature,pH,oscillation frequency and throughput)of the strains were optimized by L9(34)orthogonal design.To test their effects,the isolates were mixed(V:V=1:1,the number of bacteria was 108 CFU/ mL)and inoculated in dead-pigs + sawdust composting with different doses(0.3,0.6 and 0.9% of the wet weight of fermentation materials).The sawdust and crushed pigs were used as compost materials,single factor 4 levels 3 repeat design was carried out.Effects of adding different doses(0.3%,0.6%,0.9%)of microorganism agent(consisted of the selected strains)on compost indexes including temperature,moisture content,coliform,degradation rate,total N,total P,total K,available N,available P,available K protease,lipidase,urease and dehydrogenase were researched and then determined suitable addition amount of microorganism agent.The results showed that as follows: two thermophilic bacterial strains N-3 and Y-3 were isolated,and the strains could degrade protein and lipids,respectively.The strains N-3 and Y-3 were identified as Bacillus aestuarii and Geobacillus thermodenitrificans,and their 16 S rDNA gene sequences were 1450 bp and 1463 bp.For the strain N-3,the optional culture conditions was as follows: the temperature of 55?;pH of 7.2;roatating speed of 200r/min;throughput of 4L/min.Under optional culture conditions,the concentration was maximum for 5.87×108 CFU/mL.For the strain Y-3,when optimum temperature was 60?,pH was 7.2,roatating speed was 300r/min,and throughput was 3L/min,the maximum concentration was 6.53×108 CFU/mL.The maximum temperature adding microorganism agent reached 69.0? ? 68.9 ?and 66.3?,which were significantly higher than that of control with 58.3?(P<0.01).The days of high temperature phase(above 60?)for inoculation groups and control is 8d?10d?9d and 0d,respectively(P<0.01).The control and the inoculation groups were harmless at 15 d and 10 d respectively(P<0.01).At the end of composting,the degradation rate of the inoculation groups and the control were71.2%,75.7%,96.7% and 97.1%,respectively.the inoculation groups were significantly higher than the control(P<0.05),and the groups of 0.6%,0.9% were also significantly higher than the 0.3% group(P<0.05).But the total N were 1.80%,1.67%,1.83% and 1.69%.Total P were 1.68%,1.85%,2.11% and 2.17%.Total K were 0.53%,0.57%,0.61% and 0.60%.The available N were 2.61g/kg,2.70g/kg,2.63g/kg and 2.60g/kg.Available P were 3.40g/kg,3.59g/kg,3.82g/kg and 4.49g/kg,Available K were 3.30g/kg,3.33g/kg,3.38g/kg and 3.51g/kg,respectively.There were no significant difference between the treatment groups(P<0.05).There was a negative correlation between total N and protease,lipidase,dehydrogenase.There is no significant correlation between urease activity and total nitrogen content(P>0.05).But there is a significant correlation between temperature and protease,urease.Except the control group,there was a significantly positive correlation between the dehydrogenase activity and temperature for the treament groups.In conclusion,the inoculation of the agent made by N-3 and Y-3 can effectively promote the rising of composting temperature,maintain the composting in thermophilic stage with longer time,accelerate degradation of dead pigs,effectively kill pathogenic microoganisms,and the optimum agent content was 0.6% in this research.