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Advisor(s)
Abstract(s)
In attempts to improve the metabolic efficiency in closed photosynthetic reactors,
availability of light and CO2 are often considered as limiting factors, as they are difficult
to control in a culture. The carbon source is usually provided via bubbling of CO2-
enriched air into the culture medium; however, this procedure is not particularly
effective in terms of mass transfer. Besides, it leads to considerable waste of that gas
to the open atmosphere, which adds to operation costs. Increase in the interfacial area
of contact available for gas exchange via use of membranes might be a useful
alternative; microporous membranes, in hollow-fiber form, were tested accordingly.
Two hollow-fiber modules, different in both hydrophilicity and outer surface area, were
tested and duly compared, in terms of mass transfer, versus traditional plain bubbling.
Overall volumetric coefficients (KLa) for CO2 transfer were 1.48 10-2 min-1 for the
hydrophobic membrane, 1.33 10-2 min-1 for the hydrophilic membrane, and 7.0
10-3 min-1 for plain bubbling. A model microalga, viz. Nannochloropsis sp., was
cultivated using the two aforementioned membrane systems and plain bubbling. The
produced data showed slight (but hardly significant) increases in biomass productivity
when the hollow-fiber devices were used. However, hollow-fiber modules allow
recirculation of unused CO2, thus reducing feedstock costs. Furthermore, such indirect
way of supplying CO2 offers the additional possibility for use of lower gas pressures,
as no need to counterbalance hydrostatic heads exists.
Description
Keywords
Citation
CARVALHO, Ana P. ; MALCATA, F. Xavier - Transfer of Carbon Dioxide within Cultures of Microalgae: Plain Bubbling versus Hollow-Fiber Modules. Biotechnology Progress. ISSN 1520-6033. Vol. 17, n.º 2 (2001), p. 265-272
Publisher
American Chemical Society and American Institute of Chemical Engineers