Tissue Engineering

Plant cells: current interest pharmaceuticals: atropine, codeine, L-dopa, morphine, phytotoxin (digitalis), taxol, ubiquinone-10, vincristine, vinblastine colors or dyes: anthocyanins, saffron, shikonin flavours: vanilla, strawberry, grape, garlic fragrances: jasmine, lemon, mint, rose

Paclitaxel (Taxol) anticancer drug extracted from bark of Pacific yew (Taxus brevifolia) one patient requires three 100 year old trees semisynthetic alternative: needles and branches of common yews, extract precursor presently 30,000L suspension culture

Totipotency capacity to regenerate whole plants from undifferentiated cells (common for plants) key to micropropagation somatic embryogenesis

Tissue culture propagation whole plant cutting to solid agar development of callus root or shootplantlet suspension culturephotobioreactor

Media sucrose as Carbon/Energy source inorganic nutrients vitamins, growth regulators plant hormones (auxins, cytokinins, giberellins) 27 o C, pH 5.5 in dark “elicitors” (eg. methyl jasmonate) can cause rapid accumulation of secondary metabolites

Cell characteristics 10 – 100 μm (large) typically nonphotosynthetic in culture (sucrose as C/energy) 0.5 mmol O 2 /h-g (5-15% that of microbes) high density culture possible (70% reactor volume) 90-95% water secondary metabolites often retained in vacuole

Suspension culture characteristics lower respiration rate shear sensitive (large cells) often grow as aggregates aggregation may be important to secondary metabolism CO 2 or ethylene may be important up to 75,000L reactors have been used

Bioreactors low or moderate densities (<20 g/L) appropriate to airlift high cell density require paddle or helical-ribbon impeller difficult balance between gas composition, sparging rate and degree of agitation slow growth rate so contamination is problem