Effects of Oxygen on Anoxic Biodegradation of Benzoate during Continuous Culture

• Published in: Water environment research 2003-09, Vol.75 (5), p.434-443
• Main Authors: Çinar, Özer, Deniz, Timur, Grady, C. P. Leslie
• Format: Article
• Language: English
• Subjects: Anti-Infective Agents - metabolism; Applied sciences; Aromatic compounds; Bacteria; Bacteria - enzymology; BENZOATE; Benzoates - metabolism; BIODEGRADATION; Biodegradation, Environmental; Biological and medical sciences; Biological treatment of waters; Bioreactors; Biotechnology; Chemical oxygen demand; Cytochrome; Cytochromes; DENITRIFICATION; Electron Transport Complex IV - pharmacology; Electrons; Environment and pollution; Enzymes; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General purification processes; Hydrocarbons; Industrial applications and implications. Economical aspects; Metabolism; Microorganisms; Nitrates; Nitrogen; Oxidases; Oxidation; Oxygen; Oxygen - analysis; OXYGEN EFFECT; Pollution; Research Papers; Wastewaters; Water Purification - methods; Water treatment and pollution
• ISSN: 1061-4303; 1554-7531
• DOI: 10.2175/106143003X141231

In this study, various amounts of oxygen were added to denitrifying chemostats receiving benzoate to mimic the input of oxygen to anoxic zones of biological nutrient removal systems. The effect of oxygen on the biodegradative capability of the mixed-microbial culture for benzoate was investigated. The anoxic benzoate biodegradative capability of the culture was not significantly changed as the mass flowrate of oxygen was increased to 40% of the input benzoate chemical oxygen demand (COD) mass flowrate, but was decreased approximately 70% when the mass flowrate of oxygen was increased to 70% of the input benzoate COD mass flowrate. The decrease in the anoxic benzoate biodegradative capability was due primarily to the loss of the denitrifying enzymes (measured by the anoxic pyruvate-degrading ability) and not to the loss of the key anoxic catabolic enzyme (benzoyl-coenzyme A reductase). The proportional increase in the concentration of nitrate as the residual terminal electron acceptor and the lack of synthesis of aerobic ring-cleavage enzymes as the oxygen input to the chemostat was increased suggest that the mixed microbial culture preferred oxygen to nitrate as the terminal electron acceptor, but degraded benzoate using the anoxic metabolic pathway. The concentration of the mixed microbial culture increased as the oxygen input to the chemostat was increased, suggesting that the oxygen was used by cytochrome${\rm cbb}_{3}$rather than quinol oxidase because the energetic yield of cytochrome${\rm cbb}_{3}$is higher than that of quinol oxidase or the nitrogen oxide reductases.