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

ABSTRACT

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.