Characterization of bacterial community structure during in-vessel composting of agricultural waste by 16S rRNA sequencing

Abstract

Bacterial diversity during in-vessel (rotary drum) composting of agricultural waste was characterized using NGS-based 16S rRNA sequencing for microbial identification. The activity of the bacteria was observed to vary with the composting materials and degradation pattern. Taxonomic hits distribution at domain level revealed that 89.5% sequences belonged to bacteria, 9% to eukaryota followed by 1.4% archaea during drum composting. The lowest common ancestor (LCA) classification plot showed the high abundance of the phylum proteobacteria followed by actinobacteria in compost sample. Taxonomic hit distribution at family level showed that compost sample was enriched with Thermomonosporaceae. Thermomonospora curvata is an aerobic, cellulolytic, thermophilic Gram-positive bacterium which produces a number of industrially important compounds, i.e., cellulase, alpha-amylase, and polygalacturonate lyase. Thermomonospora family of bacteria play a major role in organic matter degradation during composting. Hence, in the present study species such as Actinomadura vinacea, Thermomonospora curvata, Actinoallomurus spadix, Actinomadura rubrobrunea. T. curvata were identified from the compost mixture, which can utilize many organic compounds such as cellulose starch, xylose or pectin. The other biggest group in compost sample was Actinobacteria with Thermoleophilum album as the most abundant species followed by Collinsella aerofaciens. The compost was stabilized with higher volatile solids reduction, lower OUR (4.49 mg/g VS/day) and CO₂ (2.28 mg/g VS/day) values at the end of 20 days. The final compost was observed with 2.31% of TKN and 4.3% of phosphorus. Finally the results indicate that degradation of agricultural waste using drum composter was dominated by Bacilli, γ, β-proteobacteria, and actinobacteria.