(ii) the optical properties of the cells; (iii) the optical path length of photobioreactor;
and (iv) the mixing degree. The photons that are not absorbed by the photosynthetic
reaction centres of the cells can be reflected or the associated energy is dissipated in
the form of heat. A basic aspect of the interaction of light and temperature is the fact
that the optimum temperature for photosynthesis increase with increasing light
intensity. Gonçalves et al. (2016) evaluated the effect of light and temperature on
the growth of microalgae (C. vulgaris, P. subcapitata, Synechocystis salina and
Microcystis aeruginosa) and nutrients uptake. In the case of C. vulgaris, these
authors found that the optimum temperature for growth was 25 °C and the optimum
daily irradiance was 208 µmol/m
2 /s.
Figure 1 presents the variation of photosynthetic rate with the luminous intensity. With the increase in the light intensity, the photosynthetic rate can reach a
value corresponding to the saturation (Richmond 2004). A further increase in the
light intensity will not result in an increase of growth rate, and it can become
unfavourable, manifesting itself by a decrease in growth rate and culminating in
photoinhibition and/or the death of culture in extreme cases.
2.3 Microalgal Culture Technology
Currently, microalgal cultivation technologies can be divided in two classes: open
systems (raceway ponds, lagoons, among others) and closed systems/
photobioreactors (tubular, bubble column and airlift) (Dasgupta et al. 2010;
Kochen 2010).
Fig. 1 Variation of photosynthetic rate with light intensity (adapted from Richmond 2004)
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A. P. de Carvalho Lopes et al.