Identification of thermophilic and mesophilic bacteria and fungi in Esfahan (Iran) municipal solid waste compost

Abstract

The thermophilic and mesophilic microbiota in compost produced from Esfahan municipal solid waste were examined at different stages of composting process from day zero to 28 days and was conducted in four different seasons. Some of the mesophilic bacteria observed in initial stages of composting process were gram negative Escherichia, Klebsiella, Aeromonas and Alcaligenes, and gram positive Enterococcus and Bacillus species. After 20 days of the composting process lower species diversity of mesophiles (only Bacillus species) were isolated, which was most likely due to the high temperature (60-68°C) condition. Some of the observed thermophilic bacteria at later stages of the process are: Bacillus subtilis, B. polymyxa, B. pumilus, B. sphaericus, and B. licheniformis from thermotolerants, and B. stearothermophilus, B. acidocaldarius, and B. schleglii from thermophiles. Among the mesophilic fungi, at the initial stages of composting process some types of yeasts and molds were isolated, but after day 20 due to high temperature condition (60-68°C), no mesophilic fungi were obtained. On the 15th day of composting the highest diversity of thermo-tolerant fungi such as Cladosporium, Aspergillus, Mucor, Rhizopus, and Absidiae spp. were observed. The results indicated that, in order to obtain a sanitary product in cold seasons, the composting process needs a longer duration and fewer turnings.