the present invention relates to a method to recover , purify and isolate polyhydroxyalkanoate biopolymers from pha - containing cell mass , which includes : solubilizing the non - pha cell mass in an acidic solution , leaving a suspension of partially crystallized pha granules ; adjusting the ph of the suspension to 7 - 11 and separating the pha solids from the dissolved non - pha cellular mass ; re - suspending the pha solids in a bleaching solution for decolorization ; and 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 .