title: Characterization of soluble microbial products (SMP) derived from glucose and phenol in dual substrate activated sludge bioreactors.
abstract: 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 (K(ow)), 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 K(ow) 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 K(ow) 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.
authors.affiliation: Department of Civil Engineering, Mississippi State University, Mississippi State, MS 39762, USA. magbanua@engr.msstate.edu
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Magbanua
authors.forename: Alan R
authors.initials: AR
authors.lastname: Bowers
mesh_terms: D048908:Aliivibrio fischeri / Q000187:drug effects; D001673:Biodegradation, Environmental; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D045424:Complex Mixtures / Q000737:chemistry / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008970:Molecular Weight; D000442:Octanols / Q000737:chemistry; D019800:Phenol / Q000378:metabolism*; D012722:Sewage / Q000382:microbiology*; D012995:Solubility; D018675:Toxicity Tests; D014865:Waste Disposal, Fluid / Q000379:methods; D014867:Water / Q000737:chemistry
chemical_list: D045424:Complex Mixtures; D000442:Octanols; D012722:Sewage; D014867:Water; D019800:Phenol; D005947:Glucose