Optimization of nitrilase production from Alcaligenes faecalis MTCC 10757 (IICT-A3): effect of inducers on substrate specificity

Abstract

Microbial nitrilases are biocatalysts of interest and the enzyme produced using various inducers exhibits altered substrate specificity, which is of great interest in bioprocess development. The aim of the present study is to investigate the nitrilase-producing Alcaligenes faecalis MTCC 10757 (IICT-A3) for its ability to transform various nitriles in the presence of different inducers after optimization of various parameters for maximum enzyme production and activity. The production of A. faecalis MTCC 10757 (IICT-A3) nitrilase was optimum with glucose (1.0%), acrylonitrile (0.1%) at pH 7.0. The nitrilase activity of A. faecalis MTCC 10757 (IICT-A3) was optimum at 35 °C, pH 8.0 and the enzyme was stable up to 6 h at 50 °C. The nitrilase enzyme produced using different inducers was investigated for substrate specificity. The enzyme hydrolyzed aliphatic, heterocyclic and aromatic nitriles with different substitutions. Acrylonitrile was the most preferred substrate (~40 U) as well as inducer. Benzonitrile was hydrolyzed with almost twofold higher relative activity than acrylonitrile when it was used as an inducer. The versatile nitrilase-producing A. faecalis MTCC 10757 (IICT-A3) exhibits efficient conversion of both aliphatic and aromatic nitriles. The aromatic nitriles, which show not much or no affinity towards nitrilase from A. faecalis, are hydrolyzed effectively with this nitrilase-producing organism. Studies are in progress to exploit this organism for synthesis of industrially important compounds.

Nitrile-metabolizing potential ofBacilluscereus strain FA12; Nitrilase production, purification, and characterization

“…Dong et al reported that 20 gL Ϫ 1 of glucose was best for biomass and the nitrilase production (Dong et al 2011). However, Nageshwar and coworkers reported that nitrilase production by Alcaligenes faecalis MTCC 10757 was maximal when glucose was used as the carbon source and the optimum glucose concentration was 10 gL Ϫ 1 (Nageshwar et al 2011).…”

“…The optimum pH for both nitrilase and biomass production was 7.0, and so, in subsequent studies the pH of the medium is adjusted to 6.0 before sterilization. Most nitrilase-producing bacteria synthesize the enzyme optimally at neutral pH (Kim et al 2009;Khandelwal et al 2007;Nageshwar et al 2011). Nageshwar and coworkers reported that the most suitable pH for nitrilase production by A. faecalis MTCC 10757 was between 7.0 and 7.5 (Nageshwar et al 2011).…”

“…Several nitrogen sources, including yeast extract, peptone, urea, and sodium nitrate at the same concentrations were also examined. In addition, several ion sources including ZnSO 4 , CuSO 4 , MnSO 4 , MgSO 4 , FeSO 4 , CoCl 2 , CaCl 2 , and NaCl at the same concentrations were also examined (Khandelwal et al 2007;Jin et al 2010;Dong et al 2011;Nageshwar et al 2011).…”

Isolation and Characterization of a Nitrile-Hydrolysing Bacterium Isoptericola variabilis RGT01

“…However, there are also reports on the constitutive nature of nitrilases as observed in Bacillus subtilis [2] and in Rhodococcus ruber [7]. Choice of inducer may affect the substrate specificity of nitrilase [16,17]. After confirming that the nitrile-hydrolysing activity was produced only in the presence of the inducer and ruling out any constitutive expression of the enzyme, the effect of different inducers on substrate specificity was studied.…”

“…The logarithmic phase of growth was concomitant with the production of nitrile-hydrolysing enzyme. In literature, acrylonitrilehydrolysing activities of various strains were: Arthrobacter nitroguajacolicus-2.02 U/mg dcw [10], Rhodococcus sp.-1.22 U/mg dcm [16] and Alcaligenes faecalis-0.04 U/mg wet cell weight [17].…”