a process for producing hydroxyalkanoate copolymers , which comprises : pre - treating a sucrose - containing feedstock in an acidic solution ; feeding the pre - treated feedstock into a bioreactor containing polyhydroxyalkanoate producing microbial cells ; cultivating the polyhydroxyalkanoate producing microbial cells to form a cell mass containing the hydroxyalkanoate copolymers ; recovering the hydroxyalkanoate copolymers from the cell mass . the pre - treating step has the main function of hydrolyzing sucrose into glucose and fructose , which in turn are converted into 4 - ketovaleric acid to give a mixture of mono - saccharides and organic precursors for microbial synthesis of hydroxyalkanoate copolymers , and particularly of phbvv ter - polymers . complex and expensive purification processes of the substrates obtained from the pre - treating step are not needed . the solutions can be directly used as the feeding solutions for microbial pha biosynthesis .