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Succession of microbial community during vigorous organic matter degradation in the primary fermentation stage of food waste composting

Nakasaki, Kiyohiko, Hirai, Hidehira, Mimoto, Hiroshi, Quyen, Tran Ngoc Minh, Koyama, Mitsuhiko, Takeda, Kazuhiro
The Science of the total environment 2019 v.671 pp. 1237-1244
Bacillales, DNA, Symbiobacterium, carbon dioxide production, composting, correspondence analysis, fermentation, food waste, microbial communities, models, organic fertilizers, organic matter, pH, rabbits, recycling, rice, temperature, thermophilic bacteria, yeasts
Composting is an advantageous method for recycling organic waste and produces organic fertilizer. Composting involves many types of microorganisms that construct complex microbial ecosystems. No previous research has attempted to determine which microorganisms commonly appear in successful (i.e. well-stabilized) composting. To produce well-stabilized compost within a short time period, accelerating organic matter decomposition during primary fermentation of composting is helpful. In this study, microbial succession during primary fermentation of composting was examined with changes in its physicochemical parameters, to identify microorganisms common in the final stage of primary fermentation in successful composting with thorough degradation of organic matter. Composting of model food wastes (mixture of commercial rabbit food and cooked rice) was conducted by inoculating organic acid-degrading mesophilic yeast and maintaining the composting temperature at 40 °C for different time periods as compost warmed, and finally maintaining it at a thermophilic temperature of 60 °C. Canonical correspondence analysis (CCA) showed clear correlations among measured parameters of pH, temperature, CO2 evolution rate, cell density of thermophilic bacteria, and microbial consortium. Moreover, high-throughput DNA analysis of compost bacteria revealed that Bacillales were dominant throughout the composting process; however, types of bacteria belonging to the order Bacillales group changed significantly as the degradation of organic matter progressed. In addition, the number of a certain group of Bacillales increased together with Symbiobacterium, a commensal bacterium, and these increased in the final stage of composting when organic matter was thoroughly degraded, irrespective of composting conditions. This finding would be useful in identifying an indicator microorganism for well-stabilized compost.