Previously, we developed a “static type” garbage treatment system whose performance exceeds that of conventional garbage treatment systems. However, we could not explain the system’s excellent performance especially from a microbial ecosystem’s stand point (Matsuda et al, 2017). Microbial activity causes the decomposition of organic materials in a garbage treatment process. However, we do not know which microbes are effective in garbage decomposition and what relationship exists between the succession of a microbial community and the decomposition of organic materials in a garbage composting process.  This study analyzed the relationship between a continuous operation garbage treatment system’s microbial community and the decomposition of organic matter and evaluated for effective microbes in the same garbage treatment system. Although many research articles have been published on the composting processes throughout the world, most of them employ batch processes and not continuous processes. Conversely, most real-world practical composting plants adopt a continuous operation system in which fresh feed is usually input once a day with continuous aeration and intermittent mixing.  To comprehensively analyze the microbial community, three different approaches were adopted in this study; 1) colony observation, 2) DNA analysis, and 3) the enzymatic activities of each colony. In our experiment, the working volume was 10 L of leaf mold and 40 g/(day L) of garbage (the organic load) was input to the reactor every day at a fixed time. Dog food with 70 % moisture content was used as a model garbage substrate. The reactor’s internal temperature, the total reactor’s weight and the sampled residue’s weight, moisture content and pH were measured before inputting garbage. Additionally, the reactor’s internal temperature was measured six hours later. The internal temperature was about 55 ℃ at the highest without heating. The organic matter decomposition rate was about 50 % and the weight reduction rate was over 90 %, implying successful garbage decomposition was achieved. The microbial composition and the number of the colonies seen on the medium plate changed every day and did not realize a “steady state.” Thus an extremely efficient microbe does not exist. Only eleven microbes were isolated; yet many more microbes must exist in the system but were not counted due to a high dilution rate. From our DNA analysis, the PCR-DGGE profile of the microbial community in the garbage residue showed that bands of isolated colonies were detected in the same positions as the bands of garbage residue, which contained all kinds of microbes. Nine microbes were identified using 16S rRNA genome from eleven isolated ones. The identified microbes were of different bacterial species and their characteristics were examined from the stand point of nutritional property and enzymatic activity.  The garbage decomposition process consists of two steps, solubilization and metabolization. Extracellular enzymes act during solubilization of solid garbage residue, and intracellular enzymes work when water-soluble substances are taken up into bacterial cells and metabolized. Protease and amylase activity were measured to assess extracellular enzymatic activity and dehydrogenase activity was measured to evaluate intracellular enzymatic activity. The enzyme activities of bacterial strains significantly differed by strain. Results from this study suggest complementary microbial activity and that Bordetella trematum, Bacillus cereus, Bacillus subtills subtills and Streptomyces thermocarboxydus effectively decompose garbage.

The mirobial decomposition process of househole waste, mainly food waste, is considered an environmentally friendly way to treat organic wastes. However, there are some problems which often occur, such as low conversion rate and bad smell generation, especially in the early stage of continuous operation systems. Rice bran has been known empirically as an acclerator or improving material for the microbial decomposition process of organic wastes. Unfortuantely, little information about the detailed findings has been obtained so far. This study intended to analyze the effect of rice bran as an activating agent in organic waste decomposition in order to minimalize the problems. Firstly, the effect of rice bran was confirmed. Reactor weight, temperature, moisture content, pH, and microbe number were measured and used as the parameters to confirm the effect of rice bran addition in the decomposition process. It was observed that the total waste reduction during the process was larger in the case of rice bran addition than that of the blank, i.e. without rice bran addition. The other parameters also showed similar tendencies, indicating that rice bran is surely capable of activating the decomposition process. Then, the growth accelerating effect for microorganisms in the composting process was examined by a cultivation test using trypticase-soy liquid medium. The microbe number in the medium with rice bran addition was higher than the medium without rice bran. Secondly, the factors contributing this effect were searched. Although we could narrow down the number of candidate constituent, among them magnesium was one of the major candidates, the precise identification was not possible, possibly because the effect of each nutrient on the microbes varies depending on the kind of microbial strain, and not a single but a combination of multiple nutrients may cause this effect. However, it was confirmed as a whole that rice bran shows a good influence on the growth of many micorbes in the composting process and accelerates the performance of decomposition.