Rhizosecretion

Drake, P.M., Chargelegue, D.M., Vine, N.D., van Dolleweerd, C.J., Obregon, P, and Ma, J.K. (2003). Rhizosecretion of a monoclonal antibody protein complex from transgenic tobacco roots. Plant Mol. Biol. 52 233-241. 

Gaume, A., Komamytsky, S., Borisjuk, N., and Raskin, 1. (2003). Rhizosecretion of recombinant proteins from plant hairy roots. Plant Cell Rep. 21, 1188-1193. 

Rhizosecretion is easy to scale up and very cost effective with respect to isolation and purification. However, the bioreactor systems used for hairy root cultures differ from those used for plant cell suspensions. Traditional bioreactor systems have recently been adapted for root culture, and this technology is now being taken to commercial scales. The most traditional system is the airlift bioreactor used for microorganisms or plant cells. This system is adapted for the culturing of roots in liquid medium. Mist culture systems have also been developed. For this technology, the volume of the culture medium is reduced and the concentration of the secreted therapeutic protein is increased. If the protein to be produced is known to be quite stable, then a less expensive hydroponic culture can be designed in a manner suitable for scale-up. 

The production of pharmaceutical proteins using hairy roots and rhizosecretion technology represents a safe and viable alternative to the use of whole plants for molecular pharming. As an example of the efficiency of this system, Medina-Bolivar and Cramer (2004) expressed the reporter protein GFP in tobacco hairy root cultures using a plastic sleeve bioreactor with a 5 L volume. Yields of 500 pg GFP/L after 21 days of incubation or 20% of total secreted protein were produced using this expression system, suggesting that rhizosecretion offers a promising production system for the production of biopharmaceuticals. 

Bais, H.P., Walker, T.S., Stermitz, F.R., Hufbauer, R.A., Vivanco, J.M. 2002. Enantiomeric-dependentphytotoxic and antimicrobial activity of ( )-catechin. A rhizosecreted racemic mixture from spotted knapweed. Plant Physiol 2003 128 1173-1179. 

Human placental alkaline phosphatase 20-28 pgg- rhizosecretion (tobacco) 80, 81... 

Three Promising Examples Tobacco (Rhizosecretion, Transfection) and Moss (Clycosylation)... 

Rhizopus oryzae lactate dehydrogenase 24 rhizosecretion 48 ribosome 13 rice 27 rifamycin 14 rituxan 213 rituximab 213 application 226 approval 225 B-cell recovery 222 clinical development 215 combination 223 development 221 EMEA 225 first phase I study 219 future applications 226, 228 IDEC 219 indications 226 interferon 224 mechanism of action 215 optimizing the dose and schedule 222 pharmacokinetic 222 phase I and I/II clinical trials 219 phase I/II 216... 

Fig. 3.6 Secretion of the biopharmaceuticais via tobacco roots. The tobacco piants are geneticaiiy modified in such a way, that the protein is secreted via the roots into the medium ( rhizosecretion ). in this exampie, the tobacco plant takes up nutrients and water from the medium and releases GFP (green fluorescent protein). Examination of root-cultivation medium by its exposure to near-ultraviolet illumination reveals the bright green-blue fluorescence characteristics of GFP in the hydroponic medium (left flask in panel lower left edge). The picture also shows a schematic drawing of the hydroponic tank, as well as tobacco plants at different growth stages, for example, callus,-fully grown and greenhouse plantation [24].

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