Acclimation of mixed cultures for phenol biodegradation

Abstract

Experiments were conducted to examine the cause of lag-phase growth during phenol degradation by mixed microbial cultures that had been acclimated to one of four substrates. Four aerated Imhoff cones were inoculated with wastewater sludge and fed one of four substrates: acetate, egg albumin, vegetable oil, or phenol. Inocula from these cones were injected into batch reactors containing phenol. Time-dependent growth was measured by two methods: most probable number (MPN) and epifluorescence microscopy (EM). The MPN technique was used to distinguish two cell concentrations: total cells and a phenol-degrading community within the total; EM was also used to count total cells. The results indicated that a lag in phenol utilization for all cultures, except the phenol-acclimated cultures, was a result of growth of a phenol-degrading subpopulation, and not due to enzyme induction of the existing population. Similar experiments were conducted using 2,4-dichlorophenol (2,4-DCP), which resulted in no growth and no degradation of 2,4-DCP.