## 1 Introduction
### Microalgae Biology
Carbon metabolism begins with the incorporation of glucose into algae cells and the addition of the phosphate group to hexose, leading to glucose 6-phosphate (Glu-6-P), which is easily accessible for cell storage, growth, and respiration. Most glucose is converted into oligosaccharides, polysaccharides, etc. In conditions lacking light, however, microalgae cannot metabolize glucose [4]. The development of microalgae for biomass generation depends on a number of factors: a few of these are light, carbon sources, and sources of supplements including nitrates, phosphates, carbohydrates, and components such as manganese, cobalt, zinc, molybdenum, etc. Ideal temperature, pH, blending within the photobioreactor, oxygen expulsion, and CO\({}_{2}\) take-up in comparable extents are also estimated. Light, temperature, nitrogen, and phosphorus are related to the development rate and lipid substance of microalgae. Hence, these parameters ought to be kept up and controlled for successful biomass generation [4]. Sunlight is essential to the development and output of microalgae. Productivity in any cultivation system is largely dependent on solar energy absorption, and microalgae growth is generally best at 200 umol/m\({}^{2}\)/s, or about 1/10 of the maximum radiation of a summer day. Microalgae's photosynthetic pigments are in charge of photosynthesis, which involves collecting light and utilizing the energy it absorbs to produce NADPH and ATP before converting CO\({}_{2}\) and water into carbohydrates. The three primary categories of pigments found in microalgae are phycobilis, carotenoids, and chlorophylls. These pigments are in charge of absorbing light into various photosynthesis-related active radiation (PAR) wavelength ranges, which fall between 400 and 700 nm in the visible spectrum. Blue light (450-475 nm) and red light (630-680 nm) are absorbed by chlorophylls, whereas light between 400 and 550 nm is absorbed by carotenoids, which include lutein, fucoxanthin, \(\alpha\)- and \(\beta\)-carotenes, and xanthophylls. However, phycobilis are primarily absorbed between 500 and 650 nm. The rate at which light is bound for photosynthesis is determined by the quantity and quality of light present in addition to each microalgae species' capacity to absorb light [6]. Temperature is also considered an important and critical factor for optimization in large-scale outdoor crop systems. Daily changes in temperature may reduce the productivity of microalgae in lipids. There is also a decrease in cell volume with increasing temperature. The optimum growing temperatures generally range between 20 \({}^{\circ}\)C and 30 \({}^{\circ}\)C. Microalgae growth is affected by changes in light intensity. Many species of microalgae can withstand temperatures as low as 15 \({}^{\circ}\)C, with reduced growth rates, and temperatures higher than optimal can lead to death. In general, low right temperatures and low seasonal temperatures lead to a significant reduction in biomass productivity. Adaptability to temperature varies depending on species. For example, freshwater microalgae, _Scenedesmus_ and _Chlorella_, can adapt to temperatures in the range of 5-35 \({}^{\circ}\)C, while the ideal range is 25-30 \({}^{\circ}\)C [4]. Depending on the type of microalgae salinity, nutrients and pH may affect the growth of their biomass. Salinity affects growth, as microalgae have their own systems for adapting to a specific salinity range. Seawater microalgae may resist higher salinity compared to freshwater microalgae. Most species of microalgae have an ideal salinity. Beneath this salinity, sodium chloride (NaCl) and sodium sulfate (NaSO\({}_{4}\)) can be included to progress development. In any case, high salinity (>6 g/L) antagonistically influences and hindersthe development rate of microalgae. The development of microalgae may also be crucially influenced by pH.