## 3 Results and Discussion
### Carbon and Nitrogen Nutrition
The authors observed a very low biomass productivity when cultivated in a medium enriched with NH\({}_{4}\)Cl, NH\({}_{4}\)NO\({}_{3}\), and (NH\({}_{4}\))\({}_{2}\)SO\({}_{4}\). However, these works did not apply pH control in the medium, which could affect the results. The use of high concentrations of NH\({}_{4}\)\({}^{+}\) as a nitrogen source appears to release H\({}^{+}\), decrease the pH, and inhibit algal growth. pH control is a very important parameter because it influences the physiological state of the cells and the growth kinetics of microalgae. For example, the optimal growth of _S. dimorphus_ was found at pH 7.0, and its growth was almost completely inhibited at pH values of 4.0, 5.0, 10.0, and 11.0 [48]. Worth mentioning is a study on another green alga, _Chlorella_, for which the authors successfully optimized cultivation to produce important secondary metabolites such as lipids. The researchers optimized the growth medium, urea, phosphate supply, and the stepwise light intensity to increase lipid  
Figure 6: Changes in the released CO\({}_{2}\) level observed during the growth of _Scenedesmacae_ alga, strain EZ-B1, under continuous light (CL) at 112.32 mol m\({}^{-2}\) day\({}^{-1}\) and different initial CO\({}_{2}\) concentrations (1%, 2%, and 4%). accumulation [44]. Because the preferred nitrogen source varies among microalgae species, research is necessary to find the optimal nitrogen source and concentration. The emphasis that researchers are currently placing on reducing the time and costs of growing microalgae of biotechnological importance is certainly justified and includes a search for fast-growing strains, the selection of media, including cheap ones, and the control of metabolism through basic cultivation factors. The selection of important parameters, such as sources of constructive and energy metabolism, is the starting point for expanding the commercialization of algal biotechnologies. Although many microalgae are cultivated heterotrophically or mixotrophically, a photoautotrophic regimen has many advantages (including the capture of carbon dioxide), but despite the existing knowledge, this regimen requires additional, enormous research attention. Thus, the optimal level of light flux with the corresponding optimal concentration of inorganic carbon is critical for growth and serves as a cornerstone for the development of efficient, large-scale technologies to produce algal biomass or their metabolites. This work confirms that algal growth kinetics and productivity are closely related to the basic parameters of controlled photoautotrophic cultivation and provides a theoretical basis that is important for controlling algal metabolism depending on the cultivation goals. All optimization models showed quite high biomass yields and major metabolic products, but it was the high PPFD regimens that resulted in the highest biomass yield  
Figure 7: Ammonium nitrogen utilization by _Scenadesemaceae_ alga, strain EZ-B1, under periodic light (Pl; **A**) and continuous light (CL; **B**). and nutrient removal. Thus, the results obtained from batch cultivation of promising alga within _Scenedesmacae_ ensure that optimized light conditions will stimulate the production of valuable algal biomass while reducing the cultivation time.