Screening Of Extreme Thermophiles And Its Application In Hyperthermophilic Composting Of Pig Carcasses

Hyperthermophilic aerobic composting refers to a new type of livestock and poultry waste treatment technology,which relies on exogenous heating to pretreat the compost at high temperature,or does not rely on exogenous heating to add extreme thermophilic bacteria for aerobic composting,and the composting temperature exceeds 70℃.Among them,hyperthermophilic composting with extreme thermophilic agents is the main technical measure to quickly realize the resource utilization of livestock and poultry solid wastes,but at the same time,the acquisition of highly efficient extreme thermophilic microorganisms restricts the development of this technology.In the early stage of the laboratory,a heat-resistant cellulose-degrading bacteria was isolated from pig carcass aerobic composting and screened by ultraviolet mutagenesis.In this study,extreme thermophilic bacteria were isolated and screened from animal carcass residues treated at90℃.The thermophilic compound bacteria were prepared with the obtained high-temperature-resistant cellulose-degrading bacteria to explore the application effect of thermophilic compound bacteria in pig carcass and straw composting.The main results are as follows:1.An extreme thermophilic strain L5 was isolated from the pyrolysis residue of animal carcass after high temperature acclimation at 80℃.It was identified as Geobacillus stearothermophilus by physiological and biochemical identification,electron microscopic observation and 16Sr DNA sequencing.The growth temperature range of the strain was 55℃～85℃,the optimum temperature was 65℃,the p H range was 6 to 8,and the optimum p H was 7.0.The optimal p H for producing lipase activity of this strain is 7.0,the optimal temperature is 70℃,and the lipase activity is 35.60±0.76U/m L;the optimum p H for amylase production by the strain is 6.5,the optimum temperature is 65°C,and the amylase activity is 9.98±0.09U/m L.2.Whole genome sequencing was performed on the screened strain L5,and KEGG pathway analysis showed that strain Geobacillus stearothermophilus L5 is involved in starch and sucrose metabolism,fat metabolism,and various nitrogen metabolism pathways.The ability of nitrogen metabolism of strains was tested under different nitrogen conditions.it was found that the main pathways involved in nitrogen metabolism were ammonia assimilation,dissimilation reduction of nitrate to ammonium and nitrification.3.The strain compatibility of the screened Geobacillus stearothermophilus and Parageobacillus thermoglucosidasius was carried out by single factor multi-level,and obtained the optimal ratio:1.0%Geobacillus stearothermophilus and 1.0%Parageobacillus thermoglucosidasius and the number of live bacteria can reach 9.02×10~9 cfu/m L.4.The hyperthermophilic composting test was carried out on pig carcass and straw,which were divided into three groups:traditional high-temperature composting(control group),addition of thermophilic compound bacteria agent,and high-temperature pretreatment.The composting process lasted 55 days,and the highest temperature was60.5℃on the 17th day in the control group,78.2℃on the 8th day in the thermophilic compound bacteria group,and 62.2℃on the 5th day in the high temperature pretreatment group.And the high temperature period of the group added with thermophile was longer than that of the control group 10 days,7 days longer than the high temperature pretreatment group;the total nitrogen content of adding thermophilic bacteria increased by 1.62%compared with the control group,and the total nitrogen increase of adding thermophilic bacteria increased by 2.10%compared with the high temperature pretreatment group;The total carbon reduction in the thermophilic bacteria group was1.90%higher than that of the control group,and 0.70%higher than that of high temperature pretreatment;the HI of the thermophilic bacteria group(humification coefficient)was 6.03%higher than that of the control group,Treatment group 1.57%.To sum up,extreme thermophilic bacteria(Geobacillus stearothermophilus)which isolated from animal high temperature residue and thermophilic cellulose bacteria(Parageobacillus thermoglucosidasius)and realized hyperthermophilic composting of pig carcasses,the ripening of the reactor was promoted and the nitrogen loss was reduced.