Proposal of Hyperthermophilic Aerobic Composting Bacteria and Their Enzymes in Space Agriculture

High-temperature compost is a promising new technology to decompose organic wastes in orbiting space stations and human-inhabiting facilities on the Moon, Mars and other planets. We developed laboratory-scale models of high-temperature composters based on hyperthermophilic aerobic bacterial ecology. Organic wastes are processed in a reaction vessel heated to 80°C by the action of soil microorganisms taken from a high-temperature compost factory. Wastes, including animal bodies and inedible parts of vegetables such as stalks or center cores of cabbage and fruits, were digested within a few days in our model reactors. In order to improve composting performance, we isolated and identified thermophilic microorganisms, which played crucial roles in degrading organic substances in the model reactors. We also isolated and purified enzymes which are capable of processing hard-to-digest proteins, namely collagen, elastin and keratin. Microbial diversity in the high-temperature compost soil cultured in the laboratory model reactors was examined by DNAs extracted from compost soil samples.