Culture Conditions for Determining Microbial Population Size Contributing to High Rate Composting of Dairy Manure by using the Dilution Agar-plate Method

Abstract

This paper describes the appropriate microbial culture conditions (agar medium, incubation temperature and incubation time), for estimating the microbial population size of bacteria and actinomycetes in dairy manure compost. A sample of dairy manure compost was prepared in a forced aeration adiabatic reactor. The microbial population sizes of the sample were then measured using the dilution agar-plate method with various culture conditions, to determine the best microbial culture condition. Four different agar mediums were tested at various incubation temperatures ranging from 20 to 70°C at 5°C intervals, to measure the population sizes of both bacteria and actinomycetes. We identified a suitable agar medium, incubation temperature and incubation time for determining the microbial population size of mesophilic and thermophilic bacteria and actinomycetes. Of particular note, we found that the optimum culture conditions for the mesophilic bacteria occurred at about 43°C, higher than temperatures that are widely accepted.