ENUMERATION AND ISOLATION OF ANAEROBIC BACTERIA IN SEWAGE DIGESTOR FLUIDS

Abstract

Examination of non-methanogenic anaerobic bacteria in sewage digestor fluid was attempted by the anaerobic roll tube method. For the enumeration of anaerobic bacteria in digestor fluid, rumen fluid-glucose-cellobiose-agar (RGCA) gave as good results as previously reported in the rumen and other ecosystems like intestines and feces, under the 100% CO₂ gas phase. However, under the mixed gas phase (95% N₂ and 5% CO₂), higher colony counts were obtained with YLS agar, which contained the supernatant of autoclaved sewage digestor fluid, than with RGCA. Colony counts of anaerobic bacteria decreased with the progress of fermentation of waste and the proportion of facultative anaerobes in the isolated anaerobes also decreased. Large variations in the distribution pattern of bacteria were usually observed between the results obtained from three digestors investigated. However, Streptococcus and Gram-negative curved rods were commonly isolated from the three digestors as predominant groups.