Optimal environment for algae and biomass multiplication

Microalgae farming has attracted much attention in recent years, due to its applications in CO2 absorption, biofuels, food, animal feed and biomolecule production. Estimates of algae populations range from 350,000 to 1,000,000 species. However, only a limited number of about 30,000 have been studied and analyzed. Microalgae are a diverse group of organisms that live in different natural habitats. Many of the studied microalgae species are photosynthetic, while only a few of them are known to grow mixed or heterotrophic. The general requirements for successful microalgae cultivation include light (photosynthetic and mixed), carbon, macronutrients such as nitrogen, phosphorus, magnesium and silicate and some micronutrients for successful culture .

Light is very important in microalgae culture. The ratio between the illuminated surface area and the volume (s/v) of the explant determines the light energy available to the explants and the light distribution to the cells in the culture. In general, the higher the s/v, the higher the cell density and volumetric yield can be achieved. High cell density reduces harvesting costs, as well as costs. However, it should be borne in mind that a high cell density can result in a less illuminated area. Therefore in the system there must be enough light to supply each cell in the culture system to maintain maximum photosynthesis and growth. This will lead to an increase in biomass volumetric yield.

Key considerations in developing nutrient formulations for growing algae:

 Nitrogen sources: Nitrates, ammonia and urea are widely used as nitrogen sources, depending on the ability of the algae to use nitrogenous substrates and the culture pH. The pH of the culture medium containing nitrate tended to increase due to proton removal (H + ), while the medium containing ammonium tended to decrease due to the accumulation of H + . The pH of the urea-containing culture remains constant, in which case the algae must be able to produce urease to utilize the urea. Algae contain 7-9% nitrogen per dry weight. Therefore, to produce 1 g of cells in 1 L of culture, a minimum of 500–600 mg/L KNO3 is required.

Minerals: These include potassium, magnesium, sodium, calcium, sulfate, and phosphate fertilizers.

Vitamins: Some algae (e.g. Euglena and Ochromonas) require vitamins such as thiamin and cobalamin.

 Total salt concentration: Depends on the ecological origin of the algae. For example, the green algae Dunaliella can only survive in an environment containing 0.5 M NaCl and the optimum salinity for growth is 2 M NaCl.

 pH: Most media are neutral or slightly acidic to prevent precipitation of calcium, magnesium and trace elements.