The present invention relates to a transformant which is transformed to express Baeyer-Villiger monooxygenase (BVMO), a method for producing C5-C14 medium-chain É-hydroxy fatty acids, ±,É-dicarboxylic acids, É-amino fatty acids, or alcohols from C16-C20 long-chain fatty acids by biotransformation using the transformant, a method for producing a fatty acid derivative having an ester group which is introduced into the chain thereof from keto fatty acid using the BVMO, and novel É-hydroxy fatty acids which are prepared by the method. Degradation products such as C5 to C14 É-hydroxy fatty acids, ±,É-dicarboxylic acids, É-amino fatty acids, alcohols can be produced in a large amount from C16 to C20 long-chain fatty acids contained in a medium by biotransformation using a transformant capable of expressing BVMO of the present invention. Therefore, it can be widely used to produce É-hydroxy fatty acids, ±,É-dicarboxylic acids, É-amino fatty acids or alcohols in a more safe and economic manner.
