Improving yield of a recombinant biologic in a Brassica hairy root
manufacturing process
Abstract
Hairy root systems have proven to be a viable alternative for
recombinant protein production. For recalcitrant proteins, maximizing
the productivity of hairy root cultures is essential. The aim of this
study was to optimize a Brassica rapa rapa hairy root process for
secretion of α-L-iduronidase (IDUA), a biologic of medical value. The
process was first optimized with hairy roots expressing eGFP. For the
biomass optimization, the highest biomass yields were achieved in
modified Gamborg B5 culture medium. For the secretion induction, the
optimized secretion media was obtained with additives (1.5g/l PVP +
1mg/l 2,4-D + 20.5g/l KNO 3) resulting in 3.4 fold eGFP
secretion when compared to the non-induced control. These optimized
conditions were applied to the IDUA-expressing hairy root clone,
confirming that the highest yields of secreted IDUA occurred when using
the already defined additive combination. The functionality of the IDUA
protein, secreted and intracellular, was confirmed with an enzymatic
activity assay. A >150-fold increase of the IDUA activity
was observed using an optimized secretion medium, compared with a
non-induced medium. We have proven that our B. rapa rapa hairy
root system can be harnessed to secrete recalcitrant proteins,
illustrating the high potential of hairy roots in plant molecular
farming.