Microalgal Biotechnology: Today’s (Green) Gold Rush - Biotechnological Applications of Microalgae - page 206

correspond to $2.66, $7.32, and $1.54, respectively (Alabi, 2009), and fermenters
are recommended. In temperate regions, the climate limits cultivation of algae in
open raceways to the warmer seasons. Alabi (2009) summarized production costs
for mass cultivation of autotrophic algae as $0.1 kg −1 to $32 kg −1 compared to the
heterotrophic cultivation ($2.0 kg −1 to $12 kg −1 ). Algal-derived biofuel technology
developed by Solix Biofuels costs about $33 per gallon, or about US$8 per liter
(Kanellos, 2009). If biofuels are produced “dirt cheap” (Haag, 2007), production of
fuel at an estimated cost of $50 or less per barrel (Huntley and Redalje, 2007) would
be economically viable.
13.3 NATIVE STRAINS, CONSORTIA OF SPECIES,
AND EXTREMOPHILES
It is easy to find algae, but finding algae suitable for biotechnology is difficult.
Currently, insufficient attention is paid to the selection of algal strains that could be
cultivated inexpensively by growing them in wastewater and under ambient condi-
tions of light and temperature. It is necessary for entrepreneurs of microalgal bio-
technology to invest in selecting algal strains and optimizing their cultivation. The
choice of commercial algal strains is of paramount importance and merits rigor-
ous investigation. Local species are well adapted to local environmental conditions,
and their utility contributes to more successful cultivation than nonnative species;
for example, a consortium of Actinastrum , Chlorella , Chlorococcum , Closterium ,
Euglena , Golenkinia, Micractinium, Nitzschia , Scenedesmus, and Spirogyra , and
two unidentified species concentrated from local ponds grew well at a dairy farm in
municipal wastewater and yielded 2.8 g m −2 lipid day −1 , which would be equivalent
to 11,000 L ha −1 y −1 (Pitman et al., 2011). Microalgal cultivation in wastewaters is cost
effective in producing algal biomass for biofuel, and it also helps in the removal of
nutrients (Craggs et al., 2011).
To date, few native species have been studied for their growth and photosyn-
thetic efficiencies; with extremophiles, this is seldom the case. For example, pho-
tosynthetic rates of the extremophiles Chlamydomonas plethora and Nitzschia
frustule, isolated from a semi-arid climate, approached their theoretical maxima
corresponding to 22.8 and 18.1 mg C mg chl a −1 h −1 and high photosynthetic effi-
ciencies (Subba Rao et al., 2005). Based on their specific growth rates at 10°C,
15°C, 25°C, and 30°C and threshold ( I 0 ) and saturation ( S ) values of irradiance
and saturation irradiance for growth, Kaeriyama et al. (2011) demonstrated the
existence of physiological races in Skeletonema species isolated from Dokai Bay,
Japan. Cultures of microalgae from tropical, subtropical, and semi-arid climates
that may have unique physiological characteristics should be studied in detail. Of
note, a marine diatom, Navicula sp. strain JPCC DA0580, and a marine green alga,
Chlorella sp. strain NKG400014, isolated in Japanese ocean waters (Matsumoto
et al., 2009) had a cell composition that yielded energy of 15.9 ± 0.2 MJ kg −1 and
26.9 ± 0.6 MJ kg −1 , respectively, which is equivalent to coal energy. Also of inter-
est is the Strain B32 Dunaliella isolated from the Bay of Bengal, which yielded a
maximum 0.68 pg carotene cell −1 while strain I3 yielded 17.54 pg carotene cell −1
(Keerthi et al . , in press).