A novel two-stage laccase application strategy to maintain enzyme activity and promote pharmaceuticals and personal care products degradation during sewage sludge composting

Laccase plays a crucial role in eliminating pharmaceuticals and personal care products (PPCPs) in different ecological system, but it could be easily decomposed or inactivated under high temperature and pH conditions during the composting process. In this work, three treatments, including Control, LAC-0 and LAC-8 (the two-stage laccase application on day 0 and 8), were investigated the effects of two-stage laccase application on the typical PPCPs degradations, also the laccase activity and the successions of bacterial community. Results revealed that two-stage laccase application significantly increased the NO 3 -N contents by 12.6 % and the TN content by 28.0 %, respectively. Meanwhile, the two-stage laccase application significantly increased the TOC degradation, and the enzymatic activities of laccase, cellulase, and urease, especially during the cooling and mature stages. In addition, the degradation rate of carbamazepine for LAC-0 and LAC-8 treatments increased by 44.7 % and 54.5 %, and ibuprofen by 64.5 % and 71.1 % relative to control, respectively. Microbial correlation analysis showed that the two-stage laccase application (LAC-8) facilitated the mutualistic relationship among the bacteria communities, and increased the negative correlations between the bacterial communities and PPCPs degradations. Furthermore, the partial least squares path model indicated that bacterial community played a directly role in the PPCPs degradation, and environmental factors and enzyme activities had an indirectly roles.