Optimization of Conditions for the Biotransformation of 5-Cyanovaleramide from Adiponitrile by Rhodococcus ruber CGMCC 3090

Abstract-Adiponitrile was regioselectively converted to 5-cyanovaleramide as the single product using resting cells of Rhodococcus ruber CGMCC3090. In this research, the reaction characteristics of regioselective biotransformation of adiponitrile to 5-cyanovaleramide using Rhodococcus ruber CGMCC3090 was studied, and the reaction conditions were optimized. As a result, the optimum reaction temperature and pH were 30°C and 7.5, respectively. The deactivation energy of the reaction was 20.91 kJ/mol according to Arrhenius equation. Bioconversion capacity was increased by 10% with adding 2.5% (V/V) methanol in the reaction system. When 10^-4 mol/L of Co²⁺ was added to the reaction system, the conversion ratio was increased by 40%. However, the enzyme activity was significantly inhibited by 10^-4 mol/L of Zn²⁺ or Cu²⁺. Under optimal conditions, 1.5 mol/L adiponitrile was converted to 5-cyanovaleramide with the cell concentration of 0.88 g/L, with the transformation ratio and regioselectiverty of both 100%.