Methods for the recovery and cation of polyhydroxyalkanoates (PHAs)from biomass containing PHAs, wherein the methods include treating the biomass or partially purified PHA with ozone, in at least one step of a purification process, have been developed. Treatment of PHA-containing biomass or partially purified PHA with ozone yields an enhanced level of purity suitable for coating and other applications. The ozone treatment also has the added advantage that be resulting PHA polymer or polymer latex is essentially odor-free. The ozone treatment may be used alone or in combination with other treatment, extraction, and separation stages, and is especially suitable for the treatment of PHA-containing latexes slurries, suspensions, and organic solutions.