Response of mixed microbial culture to 2,6-dihydroxybenzoic acid and peptone mixture at low sludge age-effect of culture history

The study evaluated the response of an enriched microbial culture on 2,6-dihydroxybenxoic acid (2,6-DHBA) and peptone mixture at low sludge age (θX) under aerobic conditions. It emphasized the effect of culture history by comparing the response of the microbial culture sustained at identical conditions but at two different θX of 2 and 10 days. The fate and impact of continuous 2,6-DHBA addition were evaluated by means of changes induced on the oxygen uptake rate profiles. The acute impact of 2,6-DHBA drastically changed with the culture history. It only inhibited the utilization of the readily biodegradableCODfraction but maintained the overall stoichiometry of substrate removal at a θX of 2 days, while blocking microbial activity with only partial substrate utilization when the θX was 10 days. After four days of continuous 2,6-DHBA feeding, the microbial culture was acclimated providing simultaneous removal for peptone and 2,6-DHBA. The acclimation period was apparently a function of the θX and it was shorter than 10 days. Evaluation of the oxygen uptake rate profiles indicated that acclimation resulted in the development of a dual microbial community with the selective growth of another group of biomass equipped with the enzymatic tools for utilizing 2,6-DHBA as an organic carbon source.