Kinetics study of pyridine biodegradation by a novel bacterial strain, Rhizobium sp. NJUST18

Abstract

Biodegradation of pyridine by a novel bacterial strain, Rhizobium sp. NJUST18, was studied in batch experiments over a wide concentration range (from 100 to 1,000 mg l⁻¹). Pyridine inhibited both growth of Rhizobium sp. NJUST18 and biodegradation of pyridine. The Haldane model could be fitted to the growth kinetics data well with the kinetic constants μ* = 0.1473 h⁻¹, K _s = 793.97 mg l⁻¹, K _i = 268.60 mg l⁻¹ and S _m = 461.80 mg l⁻¹. The true μ _max, calculated from μ*, was found to be 0.0332 h⁻¹. Yield coefficient Y _X/S depended on S _i and reached a maximum of 0.51 g g⁻¹ at S _i of 600 mg l⁻¹. V _max was calculated by fitting the pyridine consumption data with the Gompertz model. V _max increased with initial pyridine concentration up to 14.809 mg l⁻¹ h⁻¹. The q _S values, calculated from $V_{ \hbox{max} }$, were fitted with the Haldane equation, yielding q _Smax = 0.1212 g g⁻¹ h⁻¹ and q* = 0.3874 g g⁻¹ h⁻¹ at S _m′ = 507.83 mg l⁻¹, K _s′ = 558.03 mg l⁻¹, and K _i′ = 462.15 mg l⁻¹. Inhibition constants for growth and degradation rate value were in the same range. Compared with other pyridine degraders, μ _max and S _m obtained for Rhizobium sp. NJUST18 were relatively high. High K _i and K _i′ values and extremely high K _s and K _s′ values indicated that NJUST18 was able to grow on pyridine within a wide concentration range, especially at relatively high concentrations.