# Enhancement of Metabolite Production in High-Altitude Microalgal Strains by Optimized C/N/P Ratio
###### Abstract  
This study evaluated the role of C/N/P in the increase in the synthesis of carbohydrates, proteins, and lipids in two high-mountain strains of algae (_Chorella_ sp. UFPS019 and _Desmodes_ sp. UFPS021). Three carbon sources (sodium acetate, sodium carbonate, and sodium bicarbonate), and the sources of nitrogen (NaNO\({}_{3}\)) and phosphate (KH\({}_{2}\)PO\({}_{4}\) and K\({}_{2}\)HPO\({}_{4}\)) were analyzed using a surface response (3 factors, 2 levels). In _Chlorella_ sp. UFPS019, the optimal conditions to enhance the synthesis of carbohydrates were high sodium carbonate content (3.53 g/L), high KH\({}_{2}\)PO\({}_{4}\) and K\({}_{2}\)HPO\({}_{4}\) content (0.06 and 0.14 g/L, respectively), and medium-high NaNO\({}_{3}\) (0.1875 g/L). In the case of lipids, a high concentration of sodium acetate (1.19 g/L) coupled with high KH\({}_{2}\)PO\({}_{4}\) and K\({}_{2}\)HPO\({}_{4}\) content (0.056 and 0.131 g/L, respectively) and a low concentration of NaNO\({}_{3}\) (0.075 g/L) drastically induced the synthesis of lipids. In the case of _Desmodes_ sp. UFPS021, the protein content was increased using high sodium acetate (2 g/L), high KH\({}_{2}\)PO\({}_{4}\) and K\({}_{2}\)HPO\({}_{4}\) content (0.056 and 0.131 g/L, respectively), and high NaNO\({}_{3}\) concentration (0.25 g/L). These results demonstrate that the correct adjustment of the C/N/P ratio can enhance the capacity of high-mountain strains of algae to produce high concentrations of carbohydrates, proteins, and lipids. s _Applied sciences_  
11 May 2022  
The use of microalgae presents significant advantages over terrestrial crops, including high content of target products: up to 60% protein [16; 17; 18; 19], between 20-40% carbohydrates (mainly starch) [20; 21; 22], and between 20-50% lipids [23; 24; 25; 26]. Similarly, the ability of these systems to use wastewater as a nutrient source, along with their low soil requirements and high cell growth rates, have positioned them as promising alternatives to producing multiple feedstocks [27; 28; 29; 30; 31]. This is due to the rapid maturation of production technologies and the international market for specialized metabolites [32]. The number of industrially produced strains is limited to a handful of genera and species such as _Chlorella_ sp. (Chlorophyta) [33; 34; 35; 36; 22; 36], _Dunaliella salina_ (Chlorophyta) [37; 38; 39], _Haematococcus lacustris_ (formerly _Haematococcus pluvialis_) (Chlorophyta) [40; 41; 42; 43], _Nannochloropsis_ sp. (Orthophyta, Eustigmatophyceae) [44; 45; 46; 47; 48], _Phaeodactylum tricornutum_ (Bacillustiophyta) [49; 50; 51; 52; 53; 54; 55; 56], _Porphyridium_ sp. (Rhodophyta) [57; 58; 59], _Scenedesmus_ sp. (Chlorophyta) [60; 61; 62; 63], _Spirulina_ (_Arthospira_) sp. (Cyanobacteria) [62; 63; 64; 65; 66; 67; 68; 69; 70], _Tisochrysis lutea_ (Haptophyta, Coccolithophyceae) [71; 72; 73; 74; 75], and _Tetraselmis_ sp. (Chlorophyta) [72; 73; 74; 75; 76; 77; 78; 79; 80]. However, the most popular genus is _Spirulina_ (_Arthospira_) sp. According to [PERSON] et al. [81], in Europe, 222 different companies (57% of the total worldwide) are devoted to the production of _Spirulina_ biomass, with an annual production of up to 143 tons. The proper selection of microalgae strains is a key aspect in the utilization and cost reduction of biotechnological processes since native strains present greater adaptation to the environmental conditions of local ecosystems [82; 83]. High mountain lakes are remote and extreme ecosystems subject to harsh climatic conditions, characterized by low temperatures and high solar and ultraviolet radiation (UVR) [84]. These extreme conditions can give them unique characteristics such as tolerance to high radiation, high plasticity to sudden temperature changes, and the ability to deposit high concentrations of metabolites (carbohydrates, proteins, lipids, etc.).