Page 266 - Algae Anatomy, Biochemistry, and Biotechnology

Algal Culturing 249

Digital microscopy necessitates of a microscope equipped with a digital TV camera connected
to a personal computer running dedicated application software for cell recognition and cell count-
ing. It represents an automatic, reliable, and very fast approach to growth determination.

GROWTH RATE AND GENERATION TIME DETERMINATIONS
Growth curves are prepared from cell density data obtained with a hemocytometer or electronic
particle counter on cultures sampled at intervals, such as once per day, depending on the growth
rate of the alga. Plots of number of cells against time (in days) can be made, and from these
curves can be calculated specific growth rate or growth constant (m) and division or generation
time (T g ).
A typical growth curve will show a lag phase, an exponential or log phase, and a stationary or
plateau phase, where increase in density has leveled off. In the stationary phase, growth is likely
limited by resources such as light or nutrients. Growth rate (m) is calculated with the following
equation:

lnN 2 =N 1
m ¼ (6:5)
t 2 t 1
where N 2 and N 1 are number of cells at times t 2 and t 1 .
When N 2 is twice N 1 , for example, the population has undergone a doubling, the growth rate can
be expressed as

ln(2)
m ¼ (6:6)
T g

As ln(2) is equal to 0.6931, generation time can be calculated with the following equation:

T g ¼ 0:6931 m 1 (6:7)

SUGGESTED READING

Alverson, A. J., Manoylov, K. M., and Stevenson, R. J., Laboratory sources of error for algal community
attributes during sample preparation and counting, Journal of Applied Phycology, 39, 1–13, 2003.
Andersen, R. A., Ed., Algal Culturing Techniques, Elsevier Academic Press, Burlington, 2005.
Andersen, P. and Throndsen, J., Estimating cell numbers, in Hallegraeff, G. M., Anderson, D. M., and
Cembella, A. D., Eds., Manual on Harmful Marine Algae, IOC Manuals and Guides, No. 33, UNESCO
Publishing, Paris, 2003, pp. 99–129.
Apt, K. E. and Beherens, P. W., Commercial developments in microalgal biotechnology, Journal of
Phycology, 35, 215–226, 1999.
Becker, P., MicroAlgae Production Manual, http://www.mbl.edu/aquaculture
Berges, J. A., Franklin, D. J., and Harrison, P. J., Evolution of an artificial seawater medium: improvements in
enriched seawater, artificial water over the last two decades, Journal of Phycology, 37, 1138–1145, 2001.
Chilsholm, S. W., Temporal patterns of cell division in unicellular algae, in Physiological Bases
of Phytoplankton Ecology, Platt, T., Ed., Canadian Bulletin of Fishery and Acquatic Science, Vol. 210,
pp. 150–181, 1981.
Day, J. G., Conservation strategies for algae, in: Benson, E. E., Ed., Plant Conservation Biotechnology, Taylor
and Francis Ltd., London 1999, pp. 111–124.
Fogg, G. E., and Thake, B., Algal Cultures and Phytoplankton Ecology. University of Wisconsin Press,
Madison, 1987.