Comparison and optimization of poly(3-hydroxybutyrate) recovery fromAlcaligenes eutrophus and recombinantEscherichia coli

Abstract

The recovery of poly(3-hydroxybutyrate) [PHB] fromAlcaligenes eutrophus and a recombinantEscherichia coli strain harboring theA. eutrophus poly(3-hydroxyalkanoates) biosynthesis genes was studied. When PHB was recovered using sodium hypochlorite or sodium dodecyl sulfate (SDS), non-PHB cell materials (NPCM) of the recombinantE. coli seemed to be more easily digested than those ofA. eutrophus. Furthermore, viscosity increase caused by cell lysis during SDS treatment was negligible for the recombinantE. coli, whereas a very viscous suspension was formed forA. eutrophus. These results, together with our previous finding that PHB in the recombinantE. coli is far less susceptible to molecular degradation by sodium hypochlorite, suggested that the recombinantE. coli was more beneficial than A.eutrophus in terms of PHB recovery. In order to develop an easy and efficient recovery process, we adopted and optimized the SDS treatment since, with the hypochlorite treatment, we could not handle high biomass concentrations effectively. We could obtain a PHB of 95 % purity with 96 % recovery under the optimal condition of a biomass concentration of 5 %, a ratio of SDS to biomass of 0.6, a treatment time of 60 minutes, and a treatment temperature of 30°C.