Separation of Alcaligenes eutrophus cells containing poly(3-hydroxybutyrate) from fermentation broth with pretreatment using Al- and Fe-based coagulants

Alcaligenes eutrophus containing intracellular poly(3-hydroxybutyrate) was recovered from fermentation broth by centrifugation and filtration after pr etreatment with Aland Fe-based coagulants. Coagulation efficiency was large ly affected by pH, and the optimum pH's for cell recovery were about 4.6-5. 6 for the Al-based coagulants and about 5-8 for the Fe-based coagulants. Am monium ions that combined with metals to form complex compounds increased t he coagulant requirement, and the additional requirement of coagulant was f ound to be proportional to the ammonium concentration. In addition, various ligands in addition to ammonium lolls contained in the culture medium inte rfered with the coagulation reaction and increased the coagulant requiremen t also. The coagulant requirement increased with the cell concentration reg ardless of coagulant type. The polymeric coagulants such as PACS, Hi-PAX an d Ferix-3 were more effective than nonpolymeric coagulants of aluminum sulf ate and ferrous sulfate. The optimum dosages of the coagulants tested were determined over a broad range of cell concentration of 20.5-210 g/L. It was observed that the energy requirement for centrifugation could be greatly r educed with cell coagulation.