Multisubstrate kinetics of PAH mixture biodegradation: analysis in the double-logarithmic plot |
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Authors: | Mikhail Baboshin Ludmila Golovleva |
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Institution: | (1) G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms RAS, Prospekt Nauki 5, Pushchino, Moscow region, Russia |
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Abstract: | The proposed method of kinetic analysis of aqueous-phase biodegradation of polycyclic aromatic hydrocarbons (PAH) mixture
presupposes representation of kinetic curves for each pair of mixture components, S
x
and S
y
, in double-logarithmic coordinates (ln S
x
; ln S
y
). If PAH mixture conversion corresponds to the multisubstrate model with a common active site, then the graphs in double-logarithmic
coordinates are straight lines with the angular coefficients equal to the ratio of respective first-order rate constants
kxy = \fracVy Kx Ky Vx k_{x}^{y} = {\frac{{V_{y} K_{x} }}{{K_{y} V_{x} }}} , where K
x
and K
y
are half-saturation constants, V
x
and V
y
are the maximum conversion rates for substrates S
x
and S
y
; the graph slope does not depend on any concentrations and remains constant during the change of reaction rates as a result
of inhibition, induction/inactivation of enzymes or biomass growth. The formulated method has been used to analyze PAH mixture
conversion by the culture of Sphingomonas sp. VKM B-2434. It has been shown that this process does not satisfy the multisubstrate model with a single active site.
The results suggest that the strain VKM B-2434 contains at least two dioxygenases of different substrate specificity: one
enzyme converts phenanthrene and fluoranthene and the other converts acenaphthene and acenaphthylene. The ratios of first-order
rate constants have been obtained for these pairs of substrates. |
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Keywords: | |
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