Effects of turning on the microbial consortia and the in situ temperature preferences of microorganisms in a laboratory-scale swine manure composting

► A novel experimental system was developed to clarify the effects of turning. ► Microbial consortia in composting runs with and without turning were compared. ► Turning accelerated the death of enteric bacteria, including possible pathogens. ► Temperature preferences of microorganisms were determined in situ without isolation. ► Most microorganisms in the composting without turning survived in that with turning. The effects of turning on the microbial consortia during swine manure composting were investigated. To focus on microbial migration, two types of composting runs, with and without turning, were conducted. In both cases, the material was composted in three separate reactors set at 30, 50, and 70°C. For the runs with turning, the material was removed from the reactors, pooled, mixed, and redistributed daily, whereas for those without turning, the compost was agitated inside the reactors. The microbial consortia were compared by PCR-DGGE for composting without turning at different temperatures; this revealed the temperature preferences of the microorganisms, in situ – i.e., whether they were mesophilic, thermotolerant, thermophilic, or microorganisms that could adapt to a wide range of temperatures. Moreover, most of these microorganisms, except for the enteric bacteria, survived stably during composting with turning, irrespective of the temperature, and the microbial consortia became similar across the three reactors.