Decline in extractable kitasamycin during the composting of kitasamycin manufacturing waste with dairy manure and sawdust

• Kitasamycin waste with dairy manure and sawdust at a ratio of 10/70/20 was appropriate for composting.
• Extractable kitasamycin in the 10%-waste compost degraded completely.
• The diversity of the bacterial species increased in the 10%-waste compost.
• Kitasamycin residue with resistant bacteria was left in the 30%-waste compost.
• The inhibition effect of the high level of kitasamycin on composting was discussed.

The aim of this study was to propose a feasible treatment of kitasamycin manufacturing waste by examining extractable kitasamycin and evaluating its compost maturity during the composting of waste with different ratios of dairy manure and sawdust over a 40-day period (volume/volume/volume; M1, 0/80/20; M2, 10/70/20; and M3, 30/50/20). During composting, the concentration of extractable kitasamycin in kitasamycin-contaminated composts declined rapidly, and was undetectable in M2 within 15 days. M2 also achieved the highest fertility compost, which was characterised by the following final parameters: electrical conductivity, 2.34 dS cm−1; pH, 8.15; total C/N, 22.2; water-soluble NH4+, P, and K, 0.37, 3.43, and 1.05 g kg−1, respectively; and plant germination index values, 92%. Furthermore, DGGE analysis showed a dramatic increase in the diversity of bacterial species during composting. In contrast, a high concentration (121 mg kg−1) of extractable kitasamycin still remained in the M3 compost, which exerted an inhibitory effect on the composting, resulting in reduced bacterial diversity, high values of electrical conductivity and water-soluble NH4+, a low C/N ratio, and a low plant germination index value. Furthermore, 3.86 log (CFU g−1) kitasamycin-resistant bacteria were still present on day 40, indicating the biological degradation contributed to the decline of extractable kitasamycin.