To develop a biphasic system for use in plant tissue-mediated biotransformations to overcome the low water solubilities of substrates and inhibitory effects of products. Commonly-used organic solvents and ionic liquid were assayed using the biphasic system to reduce water-insoluble benzoyl cyanide by Daucus carota (wild carrot) tissue. Dibutyl phthalate was the most suitable solvent. The optimal moisture content of dibutyl phthalate, the ratio of biomass to substrate, and the concentration of benzoyl cyanide were 50 % (v/v), 100 g mM(-1), and 12 mM l(-1), respectively. Under these conditions, 91 % of molar conversion and 99 % ee of the optical purity of the product were obtained; a high (R)-cyanohydrin concentration of 1.36 g l(-1) was achieved. The proposed biphasic system can be used in industrial applications, particularly in the biotransformation of water-insoluble compounds. This method can also be used to prepare a wide range of value-added products by synthetically manipulating the final chiral (R)-mandelic acid and its derivatives.