Microalgal culture

The microalgal cultures were mixed with RO fraction to the final dilution 1 20. Algal samples were collected by mild centrifugation 72 h after addition of the RO fraction, resuspended in 5 mL of primary fixative and fixed for 2 h at room temperature. For easier manipulation, after primary fixation the algal samples were collected by centrifugation, and the pellet was resuspended in an equal volume of 4% agar in 0.1 M PIPES, pH 7.0, at about 40°C. When solid, the agar block was cut into pieces about 1 mm3. 

Ravishankar, G.A., Sarada, R., Tripathi, U., and Bhagyalakshmi, N. 2000. Production of food colors by plant cell and microalgal cultures. In Proceedings of the 4th International Symposium on Natural Colorants for Foods, Neutraceuticals, Beverages, Confectionery Cosmetics (J.F. Francis, ed.), pp. 221-252. SIC Publishing, Hamden. 

II.A.2 Maximizing Photosynthetic Efficiencies and H2 Production in Microalgal Cultures... 

Figure 2 Examples of marine microbial cultures, (a) Bacteria isolated from the English Channel, (b) Microalgal cultures of chlorophytes, cryptophytes, and haptophytes.

Ben-Amotz, A. 2004. Industrial production of microalgal cell-mass and secondary products—major industrial species Dunaliella. In Handbook of Microalgal Culture Biotechnology and Applied Phycology (A. Richmond, ed.), pp. 273-280. Blackwell Publishing, Oxford. 

Richmond, A. 2004. Handbook of Microalgal Culture Biotechnology and Applied Phycology . Blackwell Publishing, Oxford. 

Table II. PRODUCTIVITIES OF MICROALGAL CULTURES IN HIGH-RATE SEWAGE PONDS ...

Grima EM, SeviUaJMP, Perez JAS, Camacho FG A study on simultaneous photohmitation and photoinhibition in dense microalgal cultures taking into account incident and averaged irradiances, / Biotechnol 45 59—69, 1996. 

Figure 23 Light penetration in a microalgal culture neglecting wavelength dependency of light absorption, and thus assuming a constant Oy /ph as a function of depth z. The calculation of /ph is based on Lambert-Beer with a constant specific light absorption coefficient a. Parameter values based on high-light acclimated Chlorella sorokiniancr. Ox=3.33 m moix Cx= 100 moix m /ph(0) = 1 x 10 molph m s .

As discussed earlier the average specific sugar production rate of the microalgal culture must be calculated in order to assess photobioreactor volumetric productivity. The following integral therefore must be calculated ... 

Figure 25 Schematic drawing of the light gradient inside microalgal cultures and the application of the Blackman model to calculate the average specific growth rate. The microalgal culture is subdivided into two zones (1) /ph(2)>/ph,s and (2) lph z)

Ultimately a single expression for the volumetric productivity of a microalgal culture in a photobioreactors can be derived ... 

Also when employing more realistic and more complex models, such as Jassby and Platt with spectral resolution the same rule applies volumetric productivity of a photobioreactor is maximal when the biomass density is such that the photon flux density at the darkest zone of the reactor is equal to the compensation point of photoautotrophic growth. In practice it has also been confirmed that photobioreactors can be operated at maximal productivity when the biomass concentration is maintained at those levels that almost aU light is absorbed within the microalgal culture but at the back still a minimal amount of light is left to compensate for maintenance purposes (Barbera et al, 2015 Takache et al, 2012 Zijffers et al, 2010). 

Microalgae can also be grown continuously meaning that the microalgal culture is continuously harvested and the liquid volume removed is continuously replaced with fresh water with nutrients. In the case of chemostat operation the dilution rate is fixed. Assuming a constant photon flux density a steady state will be reached where the biomass concentration does not change anymore and is constant. The influent, water with nutrients, usually does not contain any microalgae. Furthermore, the liquid voltune is usually maintained constant, so Tm = Tout=fr- Finally, it wiU be assumed that the liquid inside the photobioreactor is perfectly mixed, so C om = Cx. Then the biomass balance over the photobioreactor can be simplified as follows ... 

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