Microalgal Biotechnology: Today’s (Green) Gold Rush - Biotechnological Applications of Microalgae - page 202

algal species not native to the region, and extrapolate results obtained from controlled
laboratory culture to large-scale outdoor production systems. For optimization of
harvesting algal biomass, it would be crucial to know that wide intra- and interspe-
cific variations in the biochemical constituents of microalgae exist, depending on
their growth conditions. For example, in eight algal species, the percent lipid per dry
weight ranged from 5 to 63, lipid production 10.3 to 90 mg L −1 d −1 , biomass 0.003 to
2.5 g L −1 d −1 , and biomass production on an areal basis from 0.91 to 38 g m −2 d −1 . Also,
the commercially important carotene content in Dunaliella strain B32 and strain
I3 isolated from the Bay of Bengal varied from 0.68 pg carotene per cell to 17.54 pg
carotene per cell. As microalgae are renewable, sustainable, and affordable, their
potential to produce biofuels and bioactive compounds is great. However, we argue
that (1) improvements in strain selection, particularly the extremophile microalgae
that have the required properties for large-scale biotechnology; (2) biochemical mod-
ification; (3) utility of engineered “designer algal strains”; (4) optimization of growth,
biomass production, and harvesting; and (5) enhancement of extraction of biofuel and
conversion to co-products would all be necessary to make microalgal biotechnology
an economically viable enterprise. A robust bio-economy built on a platform of inno-
vative microalgal technologies is recommended.
Photosynthetic microalgae have been cultivated (Miquel, 1893) and utilized to
support the production of animal life in the sea (Allen and Nelson, 1910). The most
common “traditional” species used for biotechnology, usually isolated from temper-
ate waters, include Botryococcus braunii, Chaetoceros calcitrans, Chlamydomonas
reinhardtii, Chlorella vulgaris , Chroomonas sp., Dunaliella bardawil, D. salina,
D. tertiolecta, Haematococcus pluvialis, Isochrysis galbana, Nannochloropsis
oculata , Neochloris oleoabundans , Phaeodactylum tricornutum, Rhodomonas sp.,
Scenedesmus obliquus, Skeletonema costatum, Spirulina maxima, and Tetraselmis
chuii . Usual practice involves the purchase of a few “traditional” species from a
culture center for large-scale propagation, although quite a few researchers are look-
ing at isolating species adapted to local environments.
In addition to utilizing algae as biofeed, there is a global surge in microalgal
biotechnology activities for commercial applications such as biofuel, bioactive com-
pounds, and bioremediation. From virtually none in 1990, the total number of publi-
cations on microalgal biotechnology leapt to 153 by June 2011; of these, 103 were on
microalgal biofuel. This surge coincides with the 1991 Gulf War, when the mind-set
of several countries changed to reduce their dependence on imported crude oil and
to enhance their energy security. The annual worldwide consumption of motor fuel
is 320 billion gallons, of which United States accounted for 44% (http://eia.doe.gov/
pub/internationjal/iea 2005/table35.xls). At the current rate of usage, the global use
of energy will increase fivefold by 2100 (Huesmann, 2000), prompting major invest-
ments in renewable energy. Since 2007, the United States alone has injected more
than $1 billion into algae-to-energy research and development.
Microalgal biotechnology has received global attention and the attributive
advantages include (1) cultivability on nonarable land, (2) bioremediation of
wastewater by growing photosynthetic algal biomass, (3) ease of access to metabolic
products that are stored intracellularly, (4) production of biofuel and value-added
co-products, and (5) carbon sequestration, a result of the accelerated growth of