Transformation ofp-hydroxybenzonitrile top-hydroxybenzoic acid using nitrilase activity ofGordonia terrae

Biotransformation of 3-cyanopyridine to nicotinic acid using whole-cell nitrilase of Gordonia terrae mutant MN12

In the present study, the Gordonia terrae was subjected to chemical mutagenesis using ethyl methane sulfonate (EMS) and methyl methane sulfonate (MMS), N-methyl-N-nitro-N-nitrosoguanidine (MNNG), 5-bromouracil (5-BU) and hydroxylamine with the aim of improving the catalytic efficiency of its nitrilase for conversion of 3-cyanopyridine to nicotinic acid. A mutant MN12 generated with MNNG exhibited increase in nitrilase activity from 0.5 U/mg dcw (dry cell weight) (in the wild G. terrae) to 1.33 U/mg dcw. Further optimizations of culture conditions using response surface methodology enhanced the enzyme production to 1.2-fold. Whole-cell catalysis was adopted for bench-scale synthesis of nicotinic acid, and 100% conversion of 100 mM 3-cyanopyridine was achieved in potassium phosphate buffer (0.1 M, pH 8.0) at 40 °C in 15 min. The whole-cell nitrilase of the mutant MN12 exhibited higher rate of product formation and volumetric productivity, i.e., 24.56 g/h/g dcw and 221 g/L as compared to 8.95 g/h/g dcw and 196.8 g/L of the wild G. terrae. The recovered product was confirmed by HPLC, FTIR and NMR analysis with high purity (> 99.9%). These results indicated that the mutant MN12 of G. terrae as whole-cell nitrilase is a very promising biocatalyst for the large-scale synthesis of nicotinic acid.

An improved process for synthesis of nicotinic acid using hyper induced whole cell nitrilase of Gordonia terrae MTCC8139

Nitrilase mediated synthesis of nicotinic acid (vitamin B3) from 3-cyanopyridine has emerged as promising viable alternative to its chemical synthesis. In the present investigation, the nitrilase production in Gordonia terrae MTCC8139 has been increased by two fold with inducer feeding approach [i.e. the addition of 0.5% (v/v) isobutyronitrile as inducer at 0, 16 and 24 h of incubation of the culture]. The use of hyper induced whole cell nitrilase of G. terrae as biocatalyst (10 U per ml reaction) to synthesize nicotinic acid from 3-cyanopyridine in a fed batch reaction at one litre scale resulted in accumulation of 1.65 M (202 g) nicotinic acid in 330 min. The catalytic productivity of hyper induced whole cell nitrilase was increased from 8.95 to 15.3 g/h/g dcw and the reaction time was reduced to half. This is the highest productivity of nicotinic acid in a nitrilase mediated process so far reported. The achievements of the present investigation will lead to mitigate the cost of nitrilase vis-a-vis nicotinic acid production at large scale.

An insight into the ecology, diversity and adaptations of Gordonia species

The bacterial genus Gordonia encompasses a variety of versatile species that have been isolated from a multitude of environments. Gordonia was described as a genus about 20 years ago, and to date, 39 different species have been identified. Gordonia is recognized for symbiotic associations with multiple hosts, including aquatic (marine and fresh water) biological forms and terrestrial invertebrates. Some Gordonia species isolated from clinical specimens are known to be opportunistic human pathogens causing secondary infections in immunocompromised and immunosuppressive individuals. They are also predominant in mangrove ecosystems and terrestrial sites. Members of the genus Gordonia are ecologically adaptable and show marked variations in their properties and products. They generate diverse bioactive compounds and produce a variety of extracellular enzymes. In addition, production of surface active compounds and carotenoid pigments allows this group of microorganisms to grow under different conditions. Several isolates from water and soil have been implicated in bioremediation of different environments and plant associated species have been explored for agricultural applications. This review highlights the prevalence of the members of this versatile genus in diverse environments, details its associations with living forms, summarizes the biotechnologically relevant products that can be obtained and discusses the salient genomic features that allow this Actinomycete to survive in different ecological niches.