Abstract
In this study, composting with the addition of lard was carried out for the purpose of isolating fat degrading microorganisms that contributed to vigorous lard degradation during composting. Microbial succession was assessed by PCR-DGGE analysis, and the bands derived from Geobacillus pallidus were observed for the compost samples that were taken when lard was degraded actively. Subsequently, G. pallidus strain L33-1, which corresponded to the bands observed in the PCR-DGGE analysis, was isolated from the compost. The strain L33-1 was then inoculated into sterilized raw material containing lard and composting was carried out to demonstrate the lard degradation activity of the L33-1. The pH of the compost decreased rapidly to a value of 5.8 and CO2 emission became extremely low, suggesting that organic matter degradation in the composting ceased. Therefore, after the inoculation of L33-1, we suppressed pH decline by introducing ammonia gas and adding calcium hydroxide. As a result, organic matter degradation in the composting proceeded vigorously, and the lard degradation ratio on a weight basis, calculated from measurements with a Soxhlet extractor, reached 92% on day 10 of composting. It was thus revealed that the suppression of pH decline was required for the degradation of lard by the strain L33-1.
