Effect of nitrate on lipid production by T. suecica, M. contortum, and C. minutissima

Abstract

Abstract:Microalgae are an alternative and sustainable source of lipids that can be used as a feedstock for biodiesel production. Nitrate is a good nitrogen source for many microalgae and affects biomass and lipid yields of microalgae. In this study, the effect of nitrate on cell growth and lipid production and composition in Monoraphidium contortum, Tetraselmis suecica, and Chlorella minutissima was investigated. Nitrate affected the production of biomass and the production and composition of lipids of the three microalgae tested. Increasing the nitrate concentration in the culture medium resulted in increased biomass production and higher biomass productivity. Furthermore, increasing the nitrate concentration resulted in a reduction in lipid content and productivity in M. contortum; however, the opposite effect was observed in T. suecica and C. minutissima cultures. diesel infrastructure for storage and distribution. Biodiesel offers several advantages over petroleumbased diesel. For example, biodiesel is a renewable and biodegradable energy resource, it produces fewer toxic emissions (carbon monoxide, aromatic compounds, hydrocarbons, particulate matter, sulfur oxides, nitrogen oxides, and metals), it is less volatile and safer to transport, store and handle, and it increases efficiency, reduces wear, and extends engine life [2,3].Currently, biodiesel is produced from vegetable oils (edible or inedible), waste oils, and animal fats. However, this practice has raised serious concerns in the international community regarding the production, price, and availability of food. Other concerns include the deforestation of large areas of land that could be used to grow oleaginous vegetables, the huge amounts of water needed for irrigation, and the inability of these biodiesel sources to meet current and future fuel demands [4,5]. A sustainable biodiesel industry needs alternative raw materials that can be obtained easily from alternative renewable and biodegradable sources, allowing continuous operation and avoiding the limitations described [6].Currently, there is a consensus that microalgae are an alternative and sustainable source of lipids that can be used as a feedstock for biodiesel production. Microalgae are suitable for this purpose because they are photosynthetic microorganisms with a simple cellular structure and are easy to culture. Furthermore, microalgae grow in a variety of environments, their growth rate is 20 to 30 times faster than other sources of biofuels, they exhibit high photosynthetic efficiency, contribute greatly to the sequestration of atmospheric CO 2 , thereby mitigating climate change, can be harvested 365 days a year, can be grown in areas unsuitable for agriculture, livestock, industry, or tourism, require smaller volumes of water than oleaginous plants and can use water unsuitable for human consumption, their intracellular lipid content is high and the productivity of lipids per unit area is considerably higher than that of oleaginous plants [7][8][9][10].Several studies have shown that...

Production of Microalgal Biomass Using Aquaculture Wastewater as Growth Medium

“…The time needed for the microalgae to enter the stationary growth phase is known to depend on the initial nitrate concentration in the culture. The relationship between the biomass growth of C. minutissima, Tetraselmis suecica, and Monoraphidium contortum and the concentration of nitrates was also confirmed by Sánchez-García et al [34].…”

“…Similar findings were reported by Gao et al [26] for C. vulgaris and S. obliquus. The presence of the nitrogenous form of nitrogen in sewage, a macronutrient that is necessary for the synthesis of amino acids, proteins, nucleic acids, and other nitrogen-containing compounds [34], was reported to favor the production of microalgal biomass. This is in line with the present study, in which the amount of biomass increased by approximately 30% in both F/2 medium and the tested wastewater after two days of breeding.…”

“…Guldhe et al [38] cultivated Chlorella sorokiniana in tilapia aquaculture wastewater and observed lower biomass productivity (0.35 g/L/day) than in synthetic BG11 medium (0.57 g/L/day). In the studies conducted by Sánchez-García et al [34], the productivity of C. minutissima biomass in the synthetic Bold's Basal Medium (BBM) ranged from 0.01 to 0.04 g/L/day depending on the initial nitrate concentration in the medium. The availability of nitrogen affects the growth of microalgae; however, the most important factor influencing the microalgal growth is carbon.…”

“…The advantage of lipids obtained from C. minutissima cells is their composition and appropriate fatty acid profile, mainly high content of triacylglycerols, which makes them extremely useful in the production of this biofuel [47]. However, not all the lipids can be converted to biodiesel, and the most desirable ones are those that are rich in oleic acid [34].…”

Enhanced microalgal lipid production with media engineering of potassium nitrate as a nitrogen source

“…The lipid accumulation increased from 8% to 17.5% in Tetraselmis suecica and 22.7% to 36.6% in Chlorella minutissima when an initial sodium nitrate concentration was increased from 57 to 225 mg L −l and from 57 to 113 mg L −l , respectively. 35 Lipid productivities of 24.66 mg L −1 day −1 and 16.11 mg L −1 have been reported by Jena et al. 2012 8 in Scenedesmus sp and Chlorella sp, respectively.…”