Biotransformation by divison-arrested and immobilized plant cells: bioconversion of monoterpenes by gamma-irradiated suspended and entrapped cells of mentha and Nicotiana.

Exposure of MENTHA cells to 500 Gy gamma-irradiation caused cell-division arrest. These irradiated cells efficiently reduced (-)menthone to (+)neomenthol with similar or higher activity than that of the corresponding non-irradiated cells. Moreover the menthone reduction capability of the irradiated cells was fully retained following immobilization by entrapment in glyoxal-crosslinked polyacrylamide-hydrazide. Gamma-irradiated cells retained their biotransformation capability for at least one week in shake-culture; thus the transformation process could be repeated several times. Efficient biotransformation carried out by irradiated plant cells seems to be a general phenomenon. In addition to the capability of irradiated MENTHA cells to reduce either (-)menthone or another precursor (geraniol), cells derived from NICOTIANA SYLVESTRIS also retained their capacity of biotransformation, after gamma-irradiation. Division-arrested and immobilized plant cells may thus allow the development of continuous biotransformation processes.