PCT No. PCT / JP97 / 00578 Sec. 371 Date Aug. 11, 1998 Sec. 102(e) Date Aug. 11, 1998 PCT Filed Feb. 27, 1997 PCT Pub. No. WO97 / 32030 PCT Pub. Date Sep. 4, 1997A process for preparing alpha -hydroxy acids represented by the general formula (II): RCH(OH)COOH (wherein R represents a
hydrogen atom, an optionally substituted C1-C6
alkyl group, an optionally substituted C2-C6 alkenyl group, an optionally substituted C1-C6
alkoxy group, an optionally substituted
aryl group, an optionally substituted aryloxy group, or an optionally substituted heterocyclic group) by allowing a
microorganism to act on alpha -hydroxy nitriles (I): RCH(OH)CN (wherein R is as defined above) to hydrolyze and convert the alpha -hydroxy nitrites to alpha -hydroxy acids (II), wherein the alpha -hydroxy acids (II) are produced and accumulated in an aqueous
solvent by a
microorganism having the concentration resistance to the alpha -hydroxy nitrites (I) and / or alpha -hydroxy acids (II) and durability preferably in the presence of a
cyanide, and harvested. According to this process, the use of the
microorganism having the concentration resistance to the alpha -hydroxy nitriles (I) and / or alpha -hydroxy acids (II) and durability high enough to permit the activity to persist for a long period of time enables alpha -hydroxy acids (II) to be accumulated in high concentrations and
cell bodies to be repeatedly used, and hence enables alpha -hydroxy acids (II) to be efficiently prepared. The addition of a
cyanide to the
reaction system results in more efficient preparation of alpha -hydroxy acids (II).