Impact of Organic Carbon on the Biodegradation of Estrone in Mixed Culture Systems

摘要

The effects of organic carbon concentrations and loading on the degradation of estrone (El) were examined under various conditions in batch reactors and membrane-coupled bioreactors (MBRs). Experiments examined effects on individual microorganisms (substrate competition and growth) and on the whole community (selection). Substrate competition with organic carbon (competitive inhibition and catabolic repression) was not a factor in El degradation (P = 0.19 and 0.29 for two different analyses). Conversely, addition of organic carbon increased El degradation rates, attributable to biomass growth in feast-famine reactors over a five-day period (P = 0.016). Subsequently, however, community dynamics controlled El degradation rates, with other organisms outcompeting El degraders. More moderate but sustained increases in El degradation rates were observed under starvation conditions. Low influent organic carbon strength was detrimental to El degradation in MBRs, where organic carbon concentration and loading were decoupled (P = 0.018). These results point to the importance of multiple substrate utilizers in El degradation. They also suggest that while initial growth of biomass depends on the presence of sufficient organic carbon, further enrichment under starvation conditions may improve El degradation capability via the growth and/or stimulation of multiple substrate utilizers rather than heterotrophs characterized by an r-strategist growth regime.