Transcript 09.Tissue Engineering Plant Cells.web

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
root or shoot
whole plant
plantlet
cutting to solid agar
development of callus
suspension culture
photobioreactor
Media
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sucrose as Carbon/Energy source
inorganic nutrients
vitamins, growth regulators
plant hormones (auxins, cytokinins,
giberellins)
• 27oC, 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 O2/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
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lower respiration rate
shear sensitive (large cells)
often grow as aggregates
aggregation may be important to
secondary metabolism
• CO2 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