Abstract
Microalgae have a wide industrial potential because of their high metabolic diversity and plasticity. Selection of optimal cultivation methods is important to optimize multi-purpose microalgal biotechnologies. In this research, Chlorella sorokiniana AM-02 that was isolated from a freshwater lake was cultured under various high photosynthetic photon flux density (PPFD) conditions and CO2 gas levels in standard Bold’s basal medium (BBM). Furthermore, a wide range of nitrate levels (180–1440 mg L−1) was tested on the growth of C. sorokiniana. Microalgae growth, pigment concentration, medium pH, exit gas composition, as well as nitrate, phosphate, and sulfate levels were measured during an experimental period. The preferred high PPFD and optimal CO2 levels were found to be 1000–1400 μmol photons m−2 s−1 and 0.5–2.0% (v/v), respectively. The addition of nitrate ions (up to 1440 mg L−1) to the standard growth medium increased final optical density (OD750), cell count, pigment concentration, and total biomass yield but decreased the initial growth rate at high nitrate levels. Our findings can serve as the basis for a robust photoautotrophic cultivation system to maximize the productivity of large-scale microalgal cultures.
Highlights
IntroductionMicroalgae-based biotechnologies have received much attention worldwide, and they are presented as complex processes for purification of air and wastewater as well as for the production of substantial amounts of lipids, polysaccharides, proteins, commercially important pigments (such as lutein and astaxanthin), and other useful products
Microalgae-based biotechnologies have received much attention worldwide, and they are presented as complex processes for purification of air and wastewater as well as for the production of substantial amounts of lipids, polysaccharides, proteins, commercially important pigments, and other useful products
A study was conducted comparing the effect of various photosynthetic photon flux density (PPFD) and CO2 concentration values on the growth of the new isolated strain C. sorokiniana strain AM-02
Summary
Microalgae-based biotechnologies have received much attention worldwide, and they are presented as complex processes for purification of air and wastewater as well as for the production of substantial amounts of lipids, polysaccharides, proteins, commercially important pigments (such as lutein and astaxanthin), and other useful products. Pharmaceuticals for various purposes, nutraceuticals, fertilizers, biodiesel, bioethanol, and biogas are obtained from different microalgae species [1,2,3,4]. The practical application of microalgae metabolic potential can be limited by certain factors, such as photoinhibition and a slow response to different light irradiance, which lead to a low yield of biomass or target products. To increase the cell growth rate, the efficiency of biomass production, and the yield of target products, which means the effectiveness of various microalgae-based technologies, light intensity, photoperiod, temperature, pH, adequacy of macro- and micronutrients, and cultivation regimen (autotrophy, heterotrophy, and mixotrophy) must be thoroughly studied [4,7,8,9].
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