Effect of Heavy Metal Salts on Propylene Oxidation by Methanotrophic Bacteria

The effect of heavy metal (HM) (Cu(II), Fe(III), Ni(II), Zn(II)) salts on propylene oxidation by the methane-oxidizing bacteria Methylococcus capsulatus (M) as a process simulating methane oxidation by methanotrophic bacteria is investigated. The reaction begins with the activation of molecular oxygen with subsequent polypropylene oxidation. Kinetic of propylene oxide accumulation affected by HM correlates with oxygen consumption and remained stable. It is found that inhibition effects of heavy metals on propylene adsorption by M. capsulatus (M) membranes differed. EPR-spectra of M. capsulatus (M) membranes indicate the presence of a copper (II) signal with g-factor of 2.05 both before and after exposure to HM. The studied metals may be arranged in the rank order of toxicity for methanotrophic bacteria as follows: Zn > Ni > Fe > Cu. It is shown for the first time that zinc enhances inhibitory effect of other metals. It is revealed that HM at concentrations exceeding TLV at least three times insignificantly delays propylene oxidation, which indicates that this species of bacteria may be promising for the development of biofilters for removal of hydrocarbons (methane, propylene) under conditions of industrial systems and heavy metal pollution.