RECOVERY AND CHARACTERIZATION OF POLY(3-HYDROXYBUTYRIC ACID) SYNTHESIZED IN ALCALIGENES-EUTROPHUS AND RECOMBINANT ESCHERICHIA-COLI

We studied recovery of poly(3-hydroxybutyric acid) (PHB) from Alcalige nes eutrophus and a recombinant Escherichia coli strain harboring the A. eutrophus poly(3-hydroxyalkanoic acid) biosynthesis genes. The amou nt of PHB degraded to a lower-molecular-weight compound in A. eutrophu s during the recovery process was significant when sodium hypochlorite was used, but the amount degraded in the recombinant E. coli strain w as negligible. However, there was no difference between the two microo rganisms in the patterns of molecular weight change when PHB was recov ered by using dispersions of a sodium hypochlorite solution and chloro form. To understand these findings, we examined purified PHB and lyoph ilized cells containing PHB by using a differential scanning calorimet er, a thermogravimetric analyzer, and nuclear magnetic resonance. The results of our analysis of lyophilized whole cells containing PHB with the differential scanning calorimeter suggested that the PHB granules in the recombinant E. coli strain were crystalline, while most of the PHB in A. eutrophus was in a mobile amorphous state. The stability of the native PHB in the recombinant E. coli strain during sodium hypoch lorite treatment seemed to be due to its crystalline morphology. In ad dition, as determined by the thermogravimetric analyzer study, lyophil ized cell powder of the recombinant E. coli strain containing PHB exhi bited greater thermal stability than purified PHB obtained by chlorofo rm extraction. The PHB preparations extracted from the two microorgani sms had identical polymer properties.