Production of (R)-(−)-mandelic acid with nitrilase immobilized on D155 resin modified by l-lysine

A novel immobilized nitrilase (I-N-l-D155) immobilized with D155 resin modified by l-lysine (L-D155) was synthesized and used in the production of (R)-(−)-mandelic acid ((R)-(−)-MA). FTIR spectra indicated that nitrilase has been introduced into L-D155 resin and the Schiff base was formed. The condition of mandelonitrile hydrolysis was optimized, the hydrolysate characteristics was executed. The characterizations of the hydrolysate illustrated the hydrolysate was (R)-(−)-mandelic acid. The hydrolysis yield of (R)-(−)-mandelic acid was 53.42 ± 0.63% with the enantiomeric excess above 99% for hydrolysis of mandelonitrile in 45 °C, pH = 9.6, I-N-l-D155/mandelonitrile = 0.5 for 5 h Km value and thermostability of I-N-l-D155 were increased by 22.74 ± 2.08% and 5 °C, respectively, compared to free nitrilase. And the enzyme activity was retained 92.48 ± 0.32% of its initial activity after continuous 15th reuse. This novel immobilized nitrilase showed potential application for (R)-(−)-mandelic acid production and might be a valuable strategy to facilitate efficiency and cost savings.