Purification of microbial b-galactosidase from Kluyveromyces fragilis by bioaffinity partitioning

this work investigated the partitioning of b-galactosidase from kluyveromyces fragilis in aqueous two-phase systems (atps) by bioaffinity. peg 4000 was chemically activated with thresyl chloride, and the biospecific ligand p-aminophenyl 1-thio-b-d-galactopyranoside (apgp) was attached to the activated peg 4000. a new two-step method for extraction and purification of the enzyme b-galactosidase from kluyveromyces fragilis was developed. in the first step, a system composed of 6% peg 4000-apgp and 8% dextran 505 was used, where b-galactosidase was strongly partitioned to the top phase (k = 2,330). in the second step, a system formed of 13% peg-apgp and 9% phosphate salt was used to revert the value of the partition coefficient of b-galactosidase (k = 2 x 10-5) in order to provide the purification and recovery of 39% of the enzyme in the bottom salt-rich phase.