Semi-continuous fermentation of solid waste in closed artificial ecosystem: Microbial diversity, function genes evaluation.

Bioregenerative Life Support System (BLSS) is a closed artificial ecosystem and could provide oxygen, food, water and other substances for space survival. Solid waste treatment is a key rate-limiting step in BLSS. In this study, solid wastes including wheat straw, human and yellow mealworm feces were disposed in a semi-continuous bio-convertor for 105 days in a ground-based experimental BLSS platform (Lunar Palace 1). Solid wastes at different periods were sampled and the microbial community variation, functional genes and metabolic pathways were analyzed. The results showed phyla Firmicutes, Bacteroidetes and Proteobacteria predominated in all samples. While microbial community structures at genus level were significantly different, indicating selective enrichment during the 105-day process. The abundance of functional gene related to carbohydrate transport and metabolism was predicted higher on 45-day and 70-day. The metabolic pathway analysis revealed the degradation mechanisms and provided evidence for metabolic regulation.