EXTRACTIVE CULTIVATION OF ESCHERICHIA-COLI USING POLY(ETHYLENE GLYCOL) PHOSPHATE AQUEOUS 2-PHASE SYSTEMS TO PRODUCE INTRACELLULAR BETA-GALACTOSIDASE

Escherichia coli cells were found to grow in poly(ethylene glycol) (PE G)/phosphate aqueous two-phase systems by selecting the phase-forming components and their concentrations, the tie-line length, and the phas e volume ratio properly. The cells cultivated up to an optical density at 660 nm of 1.0 were disrupted by ultrasonic irradiation to release and recover overproduced beta-galactosidase. The surviving cells were found to grow immediately after ultrasonic irradiation. The PEG/phosph ate (KH2-PO4-K2HPO4) system with added Na2SO4 was the one optimized fo r extractive cultivation of E. coli cells, where beta-galactosidase wa s selectively partitioned to the top phase while total soluble protein s and cells partitioned to the bottom phase. This integrated process w as extended to a semicontinuous operating mode, where the top phase co ntaining beta-galactosidase was removed following intermittent ultraso nic irradiation and the bottom phase containing cells was recycled tog ether with the new top phase solution to repeat production and recover y of beta-galactosidase.