Effect of Nitrogen Concentration on the Alkalophilic Microalga Nitzschia sp. NW129-a Promising Feedstock for the Integrated Production of Lipids and Fucoxanthin in Biorefinery

Abstract

Microalgae are considered promising resources for producing a variety of high-value-added products, especially for lipids and pigments. Alkalophilic microalgae have more advantages than other microalgae when cultured outdoors on a large scale. The present study investigated the comprehensive effects of different nitrogen concentrations on fucoxanthin (Fx), lipids accumulation and the fatty acid profile of the alkaliphilic microalgae Nitzschia sp. NW129 to evaluate the potential for simultaneous production of Fx and biofuels. Fx and Lipids amassed in a coordinated growth-dependent manner in response to various concentrations, reaching 18.18 mg g–1 and 40.67% dry weight (DW), respectively. The biomass of Nitzschia sp. NW129 was 0.58 ± 0.02 g L–1 in the medium at the concentration of 117.65 mM. The highest productivities of Fx (1.44 mg L–1 d–1) and lipid (19.95 ± 1.29 mg L–1 d–1) were obtained concurrently at this concentration. Furthermore, the fatty acid methyl esters revealed excellent biofuel properties with an appropriate value of the degree unsaturation (49.97), cetane number (62.72), and cold filter plugging point (2.37), which met the European standards for biofuel production (EN14214). These results provided a reliable strategy for further industrialization and comprehensive production of biofuel and Fx by using the alkaliphilic microalgal Nitzschia sp. NW129.

Understanding the Impact of Nitrogen Availability: A Limiting Factor for Enhancing Fucoxanthin Productivity in Microalgae Cultivation

“…Previously, the growth of Conticribra weissflogii and P. tricornutum was suppressed in the media without nitrogen supply [28,29], while Nitzchia sp. biomass was greatly reduced under limited nitrogen conditions [24]. On the contrary, the highest dry biomass of C. weissfloggii (0.75 g/L) and Nitzchia sp.…”

“…By examining the effect of various nitrogen concentrations on FX production, Afonso et al [27] indicated that an increase in initial nitrogen concentration considered resulted in the enhanced FX content in P. tricornutum. Relevant findings have also indicated this universal effect of nitrogen availability on FX accumulation in other microalgae, such as Nitzchia sp., O. aurita, and C. weissflogii species [22,24,26]. Specifically, the highest FX content (~1.5 mg/g) was obtained from C. weissflogii cultured in the 2 N group, which was 4.5 and 1.4 times higher than those in the 0 N and 1 N cultures, respectively [28].…”

“…On the contrary, the highest dry biomass of C. weissfloggii (0.75 g/L) and Nitzchia sp. (0.6 g/L) were attained by doubling nitrogen concentration in the culture media [24,28]. Under nitrogenrepleted conditions, P. tricornutum produced approximately 2.7 times higher biomass Comparison between maximum values of FX content and productivity obtained in P. tricornutum grown under various light and nitrogen conditions.…”

“…Many findings have revealed that different nitrogen concentrations can extensively alter the growth, biochemical composition, and synthesis of bioactive compounds, such as fatty acids and pigments [22,23]. In particular, the influence of nitrogen availability on fatty acids and FX, the two most abundant high-value compounds found in diatoms, has been studied extensively [24,25]. Previous studies have indicated that nitrogen limitation promotes lipid accumulation and reduces FX production.…”

Potential for the Production of Carotenoids of Interest in the Polar Diatom Fragilariopsis cylindrus

“…The unselective enrichment of the culture medium (f > f/2, Figure 8 ) additionally supported faster growth rate, stronger biomass accumulation and higher Fx production in F. cylindrus , independent of the temperature. Medium enrichment is a common way of increasing Fx production [ 94 ] (by up to 3-fold [ 97 ]), either through nitrogen [ 32 , 33 , 34 , 76 , 93 , 98 ], iron [ 97 ], silicates and/or CO 2 enrichment of the cultures [ 95 , 99 ]. Additionally, nutrient shortage, and to a larger extent environmental stresses (e.g., high salinity, UV exposure, etc.…”