Succession of keratin-degrading bacteria and associated health risks during pig manure composting

The alteration of microbial dynamics and their divergence were evaluated in bristles containing pig manure (PM) compost with different concentrations of coconut shell biochar [0% (T1), 2.5% (T2), 5.0% (T3), 7.5% (T4) and 10% (T5)] amendment. The results revealed that the CB amendment significantly increased the keratin degradation efficiency and bacterial diversity during composting. The richest bacterial diversity and the highest keratin reduction of 39.1% were observed in the PM compost with a 7.5% CB amendment. The most abundant phyla were Firmicutes and Actinobacteria (which accounted for 87.91% and 12.09%, respectively), and the superior genera were Bacilli and Clostridia (which accounted for 23.52% and 61.17%, respectively). In addition, a dimensionality analysis from principal coordinate's analysis and non-metric multidimensional scaling showed that the bacterial community had a significant divergence among the different dosages of CB. Furthermore, the correlation found in a canonical correspondence analysis illustrated that the physio-chemical environmental factors were more relevant for the bacterial community within the CB in the compost than in that in the control sample. Overall, the application of biochar for composting altered the typical selectivity for functional bacteria and further influenced the organic waste biotransformation during bristle-containing PM composting. (C) 2020 Elsevier Ltd. All rights reserved.