The present invention relates to a method to recover, purify and isolate polyhydroxyalkanoate (PHA) biopolymers from PHA-containing cell mass, which includes: (a) solubilizing the non-PHA cell mass in an acidic solution, leaving a suspension of partially crystallized PHA granules; (b) adjusting the pH of the suspension to 7-11 and separating the PHA solids from the dissolved non-PHA cellular mass; (c) re-suspending the PHA solids in a bleaching solution for decolorization; and (d) drying the resulting PHA solids. About 95% or greater of original PHA in cell mass is recovered, and the purity of PHA solids is about 97% or above. The weight average molecular mass of the purified biopolyesters is about 500 kDa or greater.