Authors:

Abstract

The objectives of this work were to isolate and characterise a heavy metal-reducing bacterium with the capability to degrade another xenobiotic; an organic pollutant. Six molybdenum-reducing bacteria from soil that can reduce sodium molybdate into the colloidal molybdenum blue (Mo-blue) were isolated. One of these isolates identified as Pseudomonas putida strain Egypt-15 was capable of growing on PEG 4000. The optimal conditions for Mo-blue production were 34 °C, pH 6.5, 20 mM molybdate, and glucose as the electron donor. The optimum concentration supporting the growth on PEG 4000 was between 600 and 800 mgL-1. PEG degradation showed a lag period of about two days and 75 % degradation of PEG 4000 was achieved on day six at 800 mgL-1. Growth on PEG 4000 at 800 mgL-1 modelled according to the modified Gompertz model gave a maximum specific growth rate of 2.216 d-1 and a lag period of 1.45 days. Growth on PEG was optimum at 30 °C and pH 7.5. The dual ability of this bacterium to detoxify molybdenum and degrade PEG is novel and will be very useful for bioremediation.

Keywords: Modified Gompertz ,   molybdenum blue ,   molybdenum-reducing bacteria, polyethylene glycol biodegradation ,   Pseudomonas putida strain Egypt-15