Characterization of soluble microbial products (SMP) derived from glucose and phenol in dual substrate activated sludge bioreactors

• Published in: Biotechnology and bioengineering Vol. 93; no. 5; pp. 862 - 870
• Main Authors: Magbanua Jr, Benjamin S., Bowers, Alan R.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 05-04-2006; Wiley; Wiley Subscription Services, Inc
• Subjects: 14C tracer experiments; Aliivibrio fischeri - drug effects; Biodegradation, Environmental; Biological and medical sciences; Biological treatment of waters; Biomass; Bioreactors - microbiology; Biotechnology; biotreatment; Complex Mixtures - chemistry; Complex Mixtures - pharmacology; Environment and pollution; Fundamental and applied biological sciences. Psychology; Glucose; Glucose - metabolism; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Industrial applications and implications. Economical aspects; Molecular Weight; molecular weight distribution; octanol-water partition coefficient; Octanols - chemistry; Phenol - metabolism; Reactors; Sewage - microbiology; Sludge; Solubility; Toxicity; Toxicity Tests; Waste Disposal, Fluid - methods; wastewater; Water - chemistry; Water treatment; Activated sludge; wastewater; Molecular weight distribution; Toxicity; Glucose; Biological purification; Characterization; biotreatment; Bioreactor; Phenol; 14C tracer experiments; Microorganism; Biological treatment; Waste water purification; octanol-water partition coefficient
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.20774

Soluble microbial products (SMP) generated by activated sludge cultures receiving a mixed feed of phenol and glucose were characterized with respect to molecular weight (MW) distribution, octanol‐water partition coefficient (Kow), and Microtox® toxicity. Short‐term batch reactor tests using 14C‐labeled substrates were performed to collect SMP derived from each substrate, while long‐term tests were performed with SMP accumulated over multiple feed cycles using fed‐batch reactors receiving non‐labeled substrates. Yield of SMP in the batch tests, 10%–20% for phenol and 2%–5% for glucose, differed for each substrate and was independent of initial concentration. The MW distribution (MWD) of SMP was independent of feed composition, and was bimodal in the < 1 kDa and 10–100 kDa MW ranges for phenol‐derived SMP and predominantly < 1 kDa for glucose‐derived SMP. In the non‐labeled tests, the fraction of SMP of MW > 100 kDa increased with the proportion of glucose in the feed. The Kow of phenol‐derived SMP was higher compared to glucose‐derived SMP, indicating that the phenol‐derived SMP were more hydrophobic. This was particularly true at an acidic pH, where the Kow was 4.2 ± 1.0 for phenol‐derived SMP versus 0.13 ± 0.13 for glucose‐derived SMP. Toxicity testing indicated that phenol‐derived SMP, exerting a mean Microtox® inhibition of 1%, were less toxic than phenol itself, and showed little correlation between toxicity and concentration. However, glucose‐derived SMP were generally more toxic than glucose itself (a non‐toxic substrate), and the toxicity increased linearly with the concentration of SMP. © 2006 Wiley Periodicals, Inc.