A process for producing a polyester, the process comprising the steps of
(1) fermenting a saccharide with a microorganism to obtain at least one
substituted .alpha.-hydroxy acid represented by the formula:
HO--CHR--COOH (wherein R represents a hydrocarbon group having 1 to 10
carbon atoms), and (2) polymerizing the substituted .alpha.-hydroxy acid
or a derivative thereof.
