Growth rate influences reductive biodegradation of the organophosphorus pesticide demeton by Corynebacterium glutamicum

The organophosphorous pesticide, demeton-S-methyl was transformed by Coryne bacterium glutamicum in co-metabolism with more readily degradable substrat es. Glucose, acetate and fructose were tested as growth substrates, and the highest demeton-S-methyl biotransformation average rate (0.78 mg l(-1) h(- 1)) and maximum instantaneous rate (1.4 mg l(-1) h(-1)) were achieved on fr uctose. This higher efficiency seems to be linked to the atypical behavior of C. glutamicum grown on fructose, characterized by a prolonged period of accelerating growth instead of a constant growth rate observed on glucose o r acetate. More precisely, for growth rates in the 0.1-0.4 h(-1) range, a d irect coupling between the specific demeton-S-methyl consumption rate and t he growth rate was demonstrated on fructose during batch -, steady state co ntinuous - or continuous cultures with a controlled transient growth rate ( accelerostat technology). The demeton-S-methyl biotransformation was more f avoured during an acceleration phase of the growth rate.