Studies On Gene Expression Related To Carbon And Nitrogen Metabolism And Microbial Diversty During Composting Process

With the action of microorganisms aerobic compost treatment of organic solid waste to produce organic fertilizer is an effective way of waste treatment and disposal in environmental protection. This research uses Cattle manure and sugarcane leaves as the raw material for aerobic compost experiment by two different forced aeration (built-in aeration and overall aeration) composting systems. The changes of Physicochemical parameters were investigated during the composting process. Quantitative analysis of carbon and nitrogen metabolism microorganisms related gene was investigated by Real-time PCR and The diversity of bacterial community was investigated by PCR-DGGE. The results of Physicochemical parameters showed that, both built-in aeration and overall aeration composting reached the highest temperature in fourth days, were 57 degrees and 53.4 degrees; The organic matter content decreased to 49.10% and 46.22% respectively; Ammonium nitrogen content showed that increased first and then decreased and tends to be stable finally; The final content of nitrate nitrogen reached 1099.67mg/kg and 1143.96mg/kg respectively.Quantitative analysis of genes related to carbon and nitrogen metabolism by real-tinme PCR, including bacterial 16SrDNA, β-glucosidase, amoA, and nxrB1, in two different aeration (built-in aeration and overall aeration) composting processes was investigated. The experimental results showed that total bacteria in built-in aeration mode was more than that of overall aeration mode; β-glucosidase gene copies in built-in aeration and overall aeration mode reached the maximum value on day 7 and. day 4, respectively, which was 4.0 and 6.2 more times than day 1, indicating strong biodegradation and carbon metabolic activity occurred during composting process. AOB content in thermophilic stage was low, and high in maturation, which may lead to a large number of ammonia nitrogen loss during this stage. High temperature had an opposite effect on the expression of nxrBl gene, and the gene expression in built-in aeration was more than overall aeration during mature period.PCR-DGGE analysis was used to study bacterial community during the composting process, and the experimental results show that, with the composting, bacterial community succession changed constantly in each period, some bacteria appeared until maturity period, and some of the bacteria exists in the whole composting process, great change succession happened during composting process.