Dear all,
I have a question about the biodegradation of alkylmethylbenzenes and compounds with a benzenebenzene moietie. Does anyone knows a general rule for degradation rates according to their isomeric form (o-,m-,p-). For instance, as a rule, does the o-methyl compounds degrades quicker than m- and p-methyl compounds ? Same question for o-,m-,p- benzyls.
Thanks in advance for your answers.
Neil
Hi Neil,
have a look at Ernesto Hernandez his work:
Article Inhibition of biogas production and biodegradability by subs...
and contact him directly regarding the existence of rules.
Good luck, Rob.
Not sure if there is a general rule because the degradation rate is going to be pathway- and organism-specific. For xylenes, an initial oxygenase attack usually leads to a similar methyl catechol intermediate. However, the ortho and para isomers have more than one pathway to ring fission.
I suggest you look up the UMinnesota/EAWAG biocattalysis/biodegradation database (http://eawag-bbd.ethz.ch/) and follow up the references given for the compound-specific pathways to get some information on rates.
Dear Farrukh,
Thanks for the advice. I already tried the Minnesota model, but at least when I tried it, it did not give any information about half-lives. Is there a way to estimate half-lives with this model ? Robert, thank you for your answer as well. I'll have to order the article.
Best regards,
Neil
Hi Neil,
Although all the isomers go away fastest by aerobic biodegradation, you need to specify the conditions, e.g., specific pure culture vs. mixed culture, substrate limited conditions for the pure compound, or the compound present in a mixture (e.g., gasoline), etc. There are some average rates reported but your experimental or field rates can vary significantly from these values.
Here is a paper from Hanadi Rifai that averages first order biodegradation rates for xylene isomers in dissolved fuel contamination in groundwater under MNA conditions (see page 341, right column for averaged zero and first order rates);
http://www.xdd-llc.com/Suarez-and-Rifai-Biodegradation-Rates-for-Fuel-Hydrocarbons-and-Chlorinated-Solvents-1999.pdf
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