Recovery of poly(3-hydroxybutyrate) from coagulated Ralstonia eutropha using a chemical digestion method

For economic recovery of poly(3-hydroxybutyrate) (PHB) from culture broths of Ralstonia eutropha containing PHB, Al-based and Fe-based coagulants were used in the pretreatment step. The coagulated cells were then separated by centrifugation, and PHB was extracted by chemical digestion with a sodium hypochlorite/chloroform dispersion solution. The practical upper limits of dosage were found to be 1,500 mg-Al/L and 1,000 mg-Fe/L, respectively, for Al- and Fe-based coagulants. When the harvested cells were treated with a 5 0% sodium hypochlorite/chloroform dispersion solution, PHB recovery and pur ity were 90-94% and 98-99%, respectively. The influence of the use of coagu lants on the PHB recovery process was found to be insignificant. Despite th e residual Al and Fe in the recovered PHB (less than 450 mg-Al/kg-PHB and 7 50 mg-Fe/kg-PHB, respectively), no detectable amounts of Al and Fe were lea ched from films made of the recovered PHB under acidic conditions. The use of Fe-based coagulants is less recommended because the Fe impurity can caus e an unwanted colorization problem in the final product.