Metagenomic analysis revealed the microbiota and metabolic function during co-composting of food waste and residual sludge for nitrogen and phosphorus transformation

Highlights: • Metagenomic analysis of FW and RS co-composting process was investigated. • Available phosphorus increased with increasing the mass ratio of residual sludge. • Mass ration of 1:1:1 pile was more conducive to glycolysis. • 2:1:1 pile was more conducive to the generation of glutamine. This paper used bagasse as a composting additive and bulking agent in order to investigate the aerobic composting process of food waste and residual sludge. Accordingly, the variations of nitrogen and phosphorus nutrients, microbiota and metabolic function during the composting process were systematically explored. Three piles with residual sludge, food waste and bagasse mass ratios of 1:1:1, 2:1:1 and 4:1:1 were set. The ammonia nitrogen content in the three compost piles were 3.18 mg/g, 4.68 mg/g and 5.84 mg/g at the end of composting. The final available phosphorus content of the three piles were 3.42 mg/g, 6.70 mg/g and 11.21 mg/g, respectively. X-ray photoelectron spectroscopy (XPS) analysis showed that absorption peaks attributed to amines, amino acids and amides appeared in the 1:1:1 pile. Metagenomic analysis of the glycolysis and ammonia transformation pathways showed that the total relative abundance of key enzyme genes for the conversion of glucose to glucose-6-phosphate in the three plies were 0.326%, 0.213% and 0.248%, respectively. The total relative abundance of 2 glutamate dehydrogenase (GDH2), glud1–2 and E1,4,1,4 dehydrogenases in the three piles was 0.125%, 0.151% and 0.160%, respectively, as the main enzymes for the mutual conversion of ammonia and glutamate.