Biomedical Engineering Reference
In-Depth Information
TABLE 5.6
Comparison of Key Design Features and Process Parameters of Open and
Closed Systems
Open Systems
Closed Systems
Species Control
Choice of species
Restricted
Flexible
Main criteria for species
selection
Growth competition
Tolerance of range of conditions
Shear resistant
Temperature tolerant
O
2
resistant
Contamination risk
High
Reduced
Sterility
None
Achievable
Light Availability
Light utilization efficiency
Low
High
Area-to-volume ratio
Low (5-10 m
−1
)
High (20-200 m
−1
)
Process Control
Mixing
Poor
Uniform
Gas transfer
Poor
Fair/high
CO
2
loss
High
Depends on pH, alkalinity,
gas recycling
O
2
build-up
Low
High
Overheating problems
Low
High
Temperature control
Harder, but cooling not as
necessary due to large volume
Easier, but cooling more often
necessary
Hydrodynamic stress
Low
High
Evaporative water loss
Surface evaporation
Depends on cooling and
sparging design
Weather dependence
High
Less
Cultivation period
Limited
Extended
Productivity
Biomass concentration
Low (<1 g L
−1
)
High (>2 g L
−1
)
Biomass productivity
Low
High
Reproducibility of production
Variable but consistent over time
Possible within certain tolerances
Cost
Capital cost
Low
High
Most costly operating
parameters
Mixing
Temperature and oxygen control
Energy input required
Low
High
Harvesting efficiency
Low due to low biomass
concentration
Higher due to high biomass
concentration
Source:
From Pulz (2001); Carvalho et al. (2006); Grobbelaar (2009); Mata et al. (2010).
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