Optimizing nitrogen source and concentration for enhanced biomass and bioproducts in Scenedesmus dimorphus

BACKGROUND: Microalgae species for industrialization are largely selected because of their high lipid and biomass productivity. Both marine and freshwater species exhibit variations in biochemical compositions (i.e. lipid, carbohydrate and protein accumulation in biomass) when cultivated under varying environmental conditions. There is very little research available on the physiological responses of N. limnetica SAG 18.99 in terms of growth rates, biomass and lipid productivity when cultivated under variant nitrogen concentrations. OBJECTIVES: The objective of this research was to observe the physiological responses of Nannochloropsis limnetica ( N. limnetica SAG 18.99) in terms of growth rates, biomass and neutral intracellular lipid when cultivated under variant nitrate concentrations. The null hypothesis was there is no significant difference in growth rate, biomass and neutral intracellular lipid productivity of N. limnetica SAG 18.99 cultivated under variant nitrate concentrations. METHODS: N. limnetica SAG 18.99 was cultivated under “normal nitrate” (3.53 M), “nitrate replete” (7.06 M), “moderate nitrate deplete” (1.765 M), and “high nitrate deplete” (0.8825 M) under the same conditions of light, pH, temperature and CO2 concentration over the duration of 14 days. The parameters measured during the cultivation were optical density to measure growth rates, flow-cytometry to measure cell concentrations/density, gravimetrical measurements for bio dry mass/biomass (BDM), ion chromatography measurements for ions/macronutrients, pH as well as sterility tests. All statistical analyses were performed using the SPSS software package (IBM statistics Version 23) and differences in data were considered significant at p < 0.05. RESULTS: Growth rates were statistically significant ( p = 0.001). Therefore, the null hypothesis was rejected. Bio dry mass was not significant ( p = 0.939). Therefore, the null hypothesis was accepted. Relative fluorescence data recorded for all of the four flasks was not significant ( p = 0.112). Therefore, the null hypothesis was accepted. pH was not statistically significant ( p > 0.05), which means it remained constant and, therefore, had no influence on the cultivation process. CONCLUSIONS: Biomass production exponentially increased in each of the four flasks throughout the cultivation. Relative fluorescence data recorded for all of the four flasks was the highest on the first couple of days during the lag phase and decelerated towards the end of the cultivation period. It was discovered that the success of the Nile red method in assessment of lipids is species dependent. Therefore, other gravimetric and chromatography methods (i.e. gas liquid chromatography, flow cytometry, low field nuclear magnetic resonance) must be employed together with or independent of it. Furthermore, the study recommends future researchers to look into the physiological responses of N. limnetica SAG 18.99 when cultivated under other macronutrient concentrations (i.e. phosphate) and variant environmental parameters (i.e. variations in light intensity, CO2).

Ten local isolates of Aureobasidium pullulans were isolated from different plant leaves. The ability of these isolates for pullulans production using production medium was investigated. The highest production of biomass and pullulans were achieved from isolates (A5, A2)with (11.93, 23.5)g/l respactivily. The effect of eight carbon and eight nitrogen sources at final concentration (5%) on biomass and pullulan production from local isolates were tested. The results showed that glucose gave maximum production of polysaccharide from isolate (A7) with (15.5g/l).While the highest production of biomass were obtained when sucrose were used as a carbon source with (14.53)g/l from isolate (A5). Lactose and xylose failed to support polysaccharide and biomass production. Also Ammonium nitrate gave highest production of polysaccharide for all isolates tested were (22.9 g/l) from (A9). While the lowest production of polysaccharide and biomass were obtained when urea was used as a nitrogen source(1.15 ,0.28 g/l)from isolates (A6, A9) respectively .The highest production of biomass was obtained in case of using ammonium sulphat as a nitrogen source with (18.97 g/l) from isolate (A9).

Using non-metric multi-dimensional scaling analysis and multi-objective optimization to evaluate green algae for production of proteins, carbohydrates, lipids, and simultaneously fix carbon dioxide

Optimization of carbon and nitrogen sources for biomass and lipid production by Chlorella saccharophila under heterotrophic conditions and development of Nile red fluorescence based method for quantification of its neutral lipid content

BACKGROUND AND OBJECTIVES: Bioenergy is a phenomenon that has attracted humans’ attention for about a century. The desirable biological properties of chlorella sp.microalgae have turned it to one of the most ideal options for the production of biodiesel. However, the economic issues must be taken into account in its industrial scale production. The present study aims to investigate chlorella sp. biomass production and growth conditions by studying the influence of glucose concentration as a carbon source, nitrate concentration as a nitrogen source and pH, as three of the most important factors. METHODS: For this purpose, design of experiment was done by response surface methodology and each factor was investigated simultaneously under glucose concentration in 2-20 g/L, nitrate concentration in 0-1 g/L and 6FINDINGS: The results indicated that carbon concentration has maximum effect on growth and biomass production. The best results were obtained in glucose concentration of 2.6-6 g/L, nitrate concentration of 0.2-0.5 g/L and pH values 7-9. Moreover, the maximum biomass production (1.31 g/L), the highest specific growth rate (0.167 1/day), and the highest biomass productivity (0.085 g/L/Day) were obtained in the following conditions: glucose concentration of 2.6 g/L, nitrate concentration of 0.5 g/L, and pH = 8. The optimal C/N ratio was determined and significant correlation was observed between pH and growth rate change. CONCLUSION: It was concluded that Chlorella sp ., if properly adjusted for both chemical and physical parameters could be a valuable source of biomass for biodiesel production in industrial scale.

To produce energy for in-house use, an aluminium smelter in Québec launched a study of mixotrophic cultivation of microalgae in its wastewaters with the objective of having an algae production company set up operations on site. To maximize lipid productivity and maintain the biological integrity of the consortium, specific nutrients need to be added to aluminium smelter wastewaters to cultivate the selected algae-bacteria consortium. A 23 factorial design was used to determine the organic carbon, nitrogen and phosphate inputs needed. Data on biomass and lipid productivity, as well as a “consortium integrity index,” were analyzed using a multiple linear regression model. The highest biomass productivity (0.93 g/L/d)and lipid productivity (0.023 g/L/d) were obtained using the highest tested concentration in nitrogen (0.200 g/L) and the lowest tested concentration in phosphate (0.003 g/L). No significant effect of the organic carbon—tested in concentrations of 1.64 g/L, 2.64 g/L, and 3.64 g/L (glucose) and added in two increments on days 5 and 7—on productivity for a starting cell density of 5 million cells/L was detected.To achieve maximal lipid production, the results suggested that biomass productivity should be prioritized rather than lipid accumulation in the cells through nitrogen starvation. The stability and integrity of the cultured consortium have to be maintained through an appropriate balance of nutrients. A low phosphate concentration increases the stability of the consortium, although part of the variation cannot be explained by the model. Finally, an analysis of fatty acid profiles showed that different concentrations in nitrogen and phosphorus impact the proportion of C18:1(n-9) and other minor fatty acids.

In this study, the growth and lipid accumulation effects of different nitrogen sources (NaNO3, KNO3, NH4Cl and CH₄N₂O) on Synechocystis sp. and Chroococcus sp. were investigated. The results revealed that NaNO3 was the most suitable nitrogen source for both species. The highest biomass production (0.63 gL−¹) and productivity (49.0 mgL−¹ day−¹) for Synechocystis sp. were obtained with NaNO3. Chroococcus sp. produced 0.49 gL−¹ biomass with NaNO3 but showed lower lipid content. For Synechocystis sp. the lipid content and lipid productivity were 27% and 13.23 mgL−¹ day−¹, respectively, while for Chroococcus sp. these values were 19.5% and 9.73 mgL−¹ day−¹, respectively. Chroococcus sp. showed the highest lipid content (21%) in urea containing medium. NH4Cl caused low biomass and lipid production in both species. NaNO3 provided the best results in terms of growth rates and cell proliferation times (Synechocystis sp.: 0.017 h−¹, 41 h; Chroococcus sp.: 0.015 h−¹, 46 h). The results emphasise that the selection of the appropriate nitrogen source is critical for microalgae biomass and lipid production.

BACKGROUNDThis study investigated the feasibility of producing pigments from Scenedesmus dimorphus using different low‐cost synthetic and alternative media. Thus the influence of nitrogen and phosphorus deficiency, different nitrogen sources and alternative culture media (wheat bran, garlic powder, wheat bran supplemented with garlic powder) on pigment and biomass production was evaluated.RESULTSAmong the three sources of nitrogen studied (ammonium sulfate, urea and sodium nitrate), urea was the cheapest efficient alternative source of nitrogen for pigment production, especially total chlorophylls (67.38 μg L−1 d−1), by this strain, without strongly affecting biomass yield. Phosphorus deficiency had no negative effect on biomass production, but improved the production of zeaxanthin and chlorophyll b by13.1% and 26.8%, respectively, compared to control. Compared to BG‐11 medium, the alternative garlic powder medium increased the biomass yield of S. dimorphus by 5.2 times, improved the productivity of xanthophylls and contributed to the accumulation of β‐carotene.Wheat bran medium was found to be efficient as a zero‐cost culture medium for the production of pigments, where S. dimorphus accumulated twice the total pigment concentration of the control, with high β‐carotene productivity (38.58 ± 11.94 μg L−1 d−1). The addition of garlic powder to wheat bran increased the biomass (3.14 g L−1) and pigment productivity (216.86 ± 2.06 μg L−1 d−1) by 28.5 and 1.4 times, respectively, but inhibited zeaxanthin biosynthesis. This alternative medium reduced biomass and pigment production costs by 99.80% and 96.21%, respectively.CONCLUSIONWheat bran supplemented with garlic powder showed good application potential for the industrial production of biomass and pigments from S. dimorphus in open cultivation systems where garlic powder might be used simultaneously for biomass and pigment accumulation, and for biological contamination control. © 2021 Society of Chemical Industry (SCI).

Deciphering role of technical bioprocess parameters for bioethanol production using microalgae.

Effects of CO2 concentration and light intensity on macromolecules accumulation of Micractinium sp.

Production of lipids biosynthesis from Tetradesmus nygaardii microalgae as a feedstock for biodiesel production

Chapter 31 - Intensive biomass production in algal bioreactors

Background/Objectives: Mixotrophic cultivation of microalgae using agro-industrial by-products as supplements offers a sustainable strategy to enhance biomass production and bioactive compound synthesis. This study aimed to evaluate the effects of different agro-industrial by-products-orange peel extract, Cladophora glomerata macroalgal hydrolysate, and solid-state fungal fermentation hydrolysate-on the growth and bioactivity of Chlorella sorokiniana. Methods: Microalgae were cultivated under mixotrophic conditions with different agro-industrial by-products as organic carbon sources. Biomass accumulation was monitored through dry weight measurements. Lipid extraction was carried out using dimethyl carbonate. The antimicrobial activity of the extracted compounds was assessed against Escherichia coli, Bacillus megaterium, and Bacillus subtilis by determining the minimal inhibitconcentrations. Results: Orange peel extract supplementation resulted in the highest biomass production. It increased dry weight by 13.86-fold compared to autotrophic conditions. Cladophora glomerata macroalgal hydrolysate followed with a 5.79-fold increase, and solid-state fungal fermentation hydrolysate showed a 4.14-fold increase. The lipophilic fraction extracted from microalgal biomass showed high yields. Orange peel extract supplementation achieved the highest extraction yield (274.36 mg/g DW). Antimicrobial activity varied based on the supplement used: biomass cultivated with orange peel extract exhibited superior activity against E. coli, whereas Cladophora glomerata macroalgal hydrolysate biomass demonstrated potent activity against B. subtilis (MIC: 5.67 g/mL). Conclusions: These findings underscore the potential of agro-industrial by-products for enhancing microalgal biomass and metabolite production. The observed antimicrobial properties highlight the application of microalgal-derived compounds in sustainable bioprocesses, supporting their use in pharmaceutical and biotechnological applications.

Given the need to improve bioenergy production processes, it is necessary to focus on low-cost culture media and environmental conditions of radiation and temperature. The Scenedesmus dimorphus species was cultured in eutrophicated lagoon water and Bayfolan 0.3% as culture media under four photoperiods with the objective of evaluating the biomass productivity, bioremediation capacity and influence of illumination on the composition and lipid content. It is concluded that the increase of light hours in the culture with eutrophicated lagoon water produces a decrease in the biomass productivity and COD removal percentage. The highest biomass productivity was obtained in photoperiod F1 (10.5:13.5) hours L:O, 0.053 ± 0.0015 g/L day and a removal of 95.6%. Bayfolan 0.3% with F2 (11.5:12.5) and F3 (12.5:11.5) did not show significant differences in the biomass productivity and COD removal. The increase in light hours in the photoperiod induced an increase of 1.01% and 2.84% of saturated fatty acids and 0.8% and 2.14% of monounsaturated fatty acids, as well as a decrease of 3.85% and 2.88% of polyunsaturated fatty acids in eutrophicated lagoon water and Bayfolan 0.3%, respectively.

The relationship between biomass production and N2 fixation under drought‐stress conditions in peanut genotypes with different levels of drought resistance is not well understood. The objective of this study was to determine the effect of drought on biomass production and N2 fixation by evaluating the relative values of these two traits under well watered and water‐stress conditions. Twelve peanut genotypes were tested under field conditions in the dry seasons of 2003/2004 and 2004/2005 in north‐east Thailand. A split‐plot design with four replications was used. Main‐plot treatments were three water regimes [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW], and sub‐plot treatments were 12 peanut lines. Data were recorded on biomass production and N2 fixation under well watered and water‐stress conditions. Genotypic variations in biomass production and N2 fixation were found at all water regimes. Biomass production and N2 fixation decreased with increasing levels of drought stress. Genotypes did not significantly differ in reductions for biomass production, but did differ for reductions in N2 fixation. High biomass production under both mild and severe drought‐stress conditions was due largely to high potential biomass production under well‐watered conditions and, to a lesser extent, the ability to maintain high biomass production under drought‐stress conditions. High N2 fixation under drought stress also was due largely to high N2 fixation under well‐watered conditions with significant but lower contributions from the ability to maintain high nitrogen fixation under drought stress. N2 fixation at FC was not correlated with the reduction in N2 fixation at 2/3 AW and 1/3 AW. Positive relationships between N2 fixed and biomass production of the tested peanut genotypes were found at both levels of drought stress, and the relationship was stronger the more severe the drought stress. These results suggested that the ability to maintain high N2 fixation under drought stress could aid peanut genotypes in maintaining high yield under water‐limited conditions.