Efficiency of magnetic immobilization for recombinant Pichia pastoris cells harvesting over consecutive production cycles

Abstract

In the current experiment, P. pastoris cells were selected as promising candidate for production of recombinant proteins and were magnetically immobilized by 3-aminopropyltriethoxysilane-coated magnetite nanoparticles (APTES@Fe3O4). The ability of immobilized cells for the production of recombinant human serum albumin (HSA) and the potency of magnetic immobilization for yeast cells recycling was evaluated over three successive batch fermentation cycles. Interestingly, magnetic immobilization resulted in 1.4-fold increase in the HAS production. The productivity was increased from 0.7 mg/mL up to one mg/mL. But, after each production cycle a significant (more than two-fold) reduction in the productivity was recorded in free and immobilized cells. Over consecutive production cycles, efficiency of magnetic immobilization was also reduced. After three production cycles, immobilization efficiency was reduced from 80% down to 64% that was due to appearance of magnetic insensitive cells. Field emission scanning electron microscopy (FESEM) analyses approved that magnetic insensitive cells are nanoparticles free cells. These free cells can be resulted from cell proliferation and detachment of nanoparticles from cells surface. These findings can be considered for development of an efficient immobilization technique to harvest yeast cells over consecutive production cycles.