D,L-Hydantoinase activity of an Ochrobactrum anthropi strain

A microorganism with the ability to release methionine from D,L-(2-methylthioethyl) hydantoin (strain 245) was isolated from soil. The aim of this study was the identification of the strain and the adjustment of the conditions of growth and of the enzymatic reaction, in order to achieve high specific activities of bioconversion of the hydantoin.

Strain 245 was identified as Ochrobactrum anthropi. The strain grew at alkaline pH (up to 10.0) and its hydantoinase activity was found to be inducible by the substrate D,L-(2-methylthioethyl) hydantoin. The enzyme is also alkalostable, with a pH optimum of 9.0. Under these conditions, hydantoinase activity was significantly enhanced and its half life prolonged when 200 mmol l-1 ammonium and phosphate were added. The addition of Ca2+, Na+, Cu2+, Co2+, Mg2+, Zn2+ or Fe3+ (0.5 mmol l-1) to the reaction mixture increased the hydantoinase activity of strain 245 up to tenfold after 24 h of incubation, compared with unamended controls.

The adequate adjustment of some environmental parameters (pH, addition of inducer, presence of ammonium, phosphate, heavy metals and other ions) can considerably increase the D, L-hydantoinase activity of strain 245.

The findings reported here set up the initial conditions for a further application of strain 245 in the production of methionine from hydantoine.