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[Display omitted] • Optimization of microalgae culture through a two-stage cultivation strategy. • Biomass accumulation was enhanced by 23.62% under optimal conditions. • Optimal dual stress enhanced lipid and SFA content by 128.38% and 56.30%. • Microalgae recycling efficiency increased under dual stress environments. In this study, a two-stage culture strategy was refined to concurrently enhance the growth and lipid accumulation of Tetradesmus obliquus. The results unveiled that, during the initial stage, the optimal conditions for biomass accumulation were achieved with 0.02 mg·L−1 Cu2+ concentration and red light. Under these conditions, biomass accumulation reached 0.628 g·L−1, marking a substantial 23.62 % increase compared to the control group. In the second stage, the optimal conditions for lipid accumulation were identified as 0.5 mg·L−1 Cu2+ concentration and red light, achieving 64.25 mg·g−1·d−1 and marking a 128.38 % increase over the control. Furthermore, the fatty acid analysis results revealed an 18.85 % increase in the saturated fatty acid content, indicating enhanced combustion performance of microalgae cultivated under the dual stress of red light and 0.5 mg·L−1 Cu2+. This study offers insights into the potential application of Tetradesmus obliquus in biofuel production. [ABSTRACT FROM AUTHOR]

[Display omitted] • C. sorokiniana showed superior tolerance capacity on high acetate dosage up to 30 g/L. • Heterotrophy benefits to algal growth and lipogenesis when supplying 20 g/L acetate. • Inhibition of photosynthesis led to poor mixotrophic growth under 20 g/L acetate. • Heterotrophy produced superior amino acid profiling and more linoleic acid (50%). • Heterotrophic repeat fed-batch mode resulted in 23.4 g/L biomass and 7.0 g/L lipid. The low-cost carbon source, acetate, was utilized to feed a linoleic acid-rich Chlorella sorokiniana for microalgal biomass and lipid accumulation. Remarkably high tolerance capability to high acetate dosage up to 30 g/L was observed, with heterotrophy being the preferred trophic mode for algal growth and lipogenesis when supplemented 20 g/L acetate. Transcriptome analysis revealed a marked activation of pathways involved in acetate bioconversion and lipogenesis upon exposure to high-level of acetate. However, the enhancement of photorespiration inhibited photosynthesis, which ultimately led to a decrease in biomass and lipid under mixotrophy. Heterotrophic acetate-feeding generated more superior amino acid profiling of algal biomass and a predominant linoleic acid content (50 %). Heterotrophic repeat fed-batch strategy in 5 L fermenter significantly increased the growth performance and lipid titer, with the highest levels achieved being 23.4 g/L and 7.0 g/L, respectively. This work provides a viable approach for bio-products production through acetate-based heterotrophic algal cultivation. [ABSTRACT FROM AUTHOR]

• Bioremediation with flue gas CO 2 utilization potential of Chlorella was tested. • Wastewater cocktail based biodiesel and lutein production in open raceway ponds. • 100% nitrogenous substance with 85–91% carbon-phosphorus remediation were obtained. • Biomass and lutein productivity of 6.21 ± 0.16, 1.2 ± 0.08 g m−2 day−1 was achieved. • Two-fold increase in lipid content and 80.74 ± 0.07 mg L−1 day−1 CO 2 was utilized. We evaluated wastewater remediation and CO 2 utilization potential of Chlorella minutissima from flue gas in a raceway pond, while synthesizing lutein and lipid for potential healthcare and biofuel application. A mix of 20% kitchen waste, 10 g L−1 of poultry litter waste and 5% flue gas was maintained while cultivating the microalga. Complete removal of nitrate, nitrite and ammonium, 85% carbon and 91% phosphorus was observed. An average areal biomass productivity of 4.06 ± 0.12 g m−2 day−1 with a specific growth rate of 0.34 ± 0.03 day−1 was observed within 9 days. Biomass productivity of 6.21 ± 0.16 g m−2 day−1 with a specific growth rate of 0.34 ± 0.03 day−1 was achieved during winter. Furthermore, lipid content with appropriate fatty acid composition 1.04:1 (saturation:unsaturation) increased from 25% to 58%. Additionally, lutein productivity of 1.2 ± 0.08 mgL−1 day−1, while utilizing 80.74 ± 0.07 mg L−1 day−1 of CO 2 from 5% flue gas was obtained. [ABSTRACT FROM AUTHOR]

Direct disposal of vinasse, a by-product of molasses fermentation plants, threatens environmental health. This study investigated the usage of vinasse as a nutrient source for the heterotrophic and mixotrophic cultivation of novel Micractinium sp. ME05. The 500-mL flask experiments resulted in higher biomass productivities under mixotrophic conditions (0.16 ± 0.01 g L −1  day 1 ) than the heterotrophic conditions (0.13 ± 0.01 g L −1  day 1 ). A 1.7-fold increase in biomass productivity was achieved by scaling up from 500-mL flasks (0.16 ± 0.01 g L −1  day 1 ) to 2-L flasks (0.27 ± 0.019 g L −1  day 1 ). The 5-L bioreactor experiments resulted in a biomass productivity of 0.32 ± 0.2 g L −1  day 1 and lipid productivity of 3.4 ± 0.20 g L −1  day −1 . This study demonstrated that Micractinium sp . ME05 can be cultivated with vinasse to produce large amounts of biomass. The FAME profile of mixotrophic Micractinium sp. ME05 cells was promising for further biodiesel production. This study highlights the feasibility of industrial by- product-vinasse as the nutrient source for biomass and lipid productions using the novel Micractinium sp. ME05 cells. [ABSTRACT FROM AUTHOR]

Alcohol wastewater (AW) as carbon source for enhancing Chlorella pyrenoidosa growth and lipid accumulation in anaerobically digested starch wastewater (ADSW) was performed in outdoor cultivation. The biomass and lipid production significantly increased while adding optimal amount of AW (AW/ADSW = 1:15) during exponential phase. In comparison with blank ADSW culture, the optimal AW addition increased the biomass production, lipid content and productivity by 35.29%, 102.68% and 227.91%, respectively. However, AW addition caused severe bacterial contamination and the total bacterial increased by 4.62-fold. Simultaneously, the optimal consortia of microalgae/bacteria effectively removed nutrients from the wastewater, including 405.18 ± 36.47 mg COD Cr /L/day, 49.15 ± 5.54 mg N/L/day and 6.72 ± 1.24 mg P/L/day. [ABSTRACT FROM AUTHOR]

The aim of the present work was to evaluate the feasibility of microalgae cultivation using secondary treated domestic wastewater. Two Chlorella vulgaris strains (CICESE and UTEX) and an indigenous consortium, were cultivated on treated wastewater enriched with and without the fertilizer Bayfolan®. Biomass production for C. vulgaris UTEX, CICESE and the indigenous consortium grown in treated wastewater was 1.167 ± 0.057, 1.575 ± 0.434 and 1.125 ± 0.250 g/L, with a total lipid content of 25.70 ± 1.24, 23.35 ± 3.01and 20.54 ± 1.23% dw, respectively. The fatty acids profiles were mainly composed of C16 and C18. Regardless of the media used, in all three strains unsaturated fatty acids were the main FAME (fatty acids methyl esters) accumulated in a range of 45–62%. An enrichment of treated wastewater with Bayfolan® significantly increased the production of biomass along with an increase in pigments and proteins of ten and threefold, respectively. [ABSTRACT FROM AUTHOR]

Switching cultivation (mixotrophic-heterotrophic, 12 h:12 h) of Heynigia riparia SX01 was studied, the maximum biomass concentration of 3.55 g L −1 and lipid yield of 1.45 g L −1 were achieved after 8 days cultivation. The extracellular polymeric substance (EPS) was developed as co-product. Addition of MgSO 4 could enhance the production of EPS. The highest amount of 0.60 g L −1 EPS was obtained with the addition of 2 g L −1 MgSO 4 , the self-flocculation efficiency was as high as 83% at this condition. The total lipid and lipid fractions did not show differences with extra MgSO 4 . Based on the above results, a new biodiesel production model was proposed: culturing Heynigia riparia SX01 with extra 2 g L −1 MgSO 4 by switching cultivation and using self flocculation to collect microalgae for biodiesel production, while EPS was collected as valuable co-products. [ABSTRACT FROM AUTHOR]

In this study, the toxicity of ammonium was removed in the microalga Nannochloropsis oculata by using acetate as a carbon source. Algal biomass and lipid production were significantly enhanced when N. oculata was grew on 0.5–50 mM of ammonium and 16–64 mM of acetate in mixotrophic conditions. When grown mixotrophically on 1 mM of ammonium and 32 mM of acetate, the biomass and lipid production reached 543 mg/L and 279 mg/L respectively, which were 1.5 and 9.4 times higher than the levels generated when grown autotrophically on nitrate. This suggests that mixotrophic growth with acetate can be a useful method to enhance microalgal lipid production. [ABSTRACT FROM AUTHOR]

The present study was conducted with microalga Nannochloropsis sp. to evaluate its tolerance responses and biofuel perspectives under different arsenic regime (0–1000 μM As(III)). Results showed that optimal biomass (61.00 ± 3.72 mg/L/d) and lipid productivity (20.27 mg/L/d) were obtained in culture treated with 100 μM As(III) in comparison to other treatments. In addition, fatty acid profile of alga was in accordance with European biodiesel standards (EN 14214), which reflects good oxidative stability of oil. High antioxidants viz., ascorbic acid, GSH and cysteine tolerance responses as well as lipid yield at 100 μM As(III), opens a new insight in the field of algal biology. Thus, microalgae Nannochloropsis sp. may be employ in remediation as well as biodiesel production. [ABSTRACT FROM AUTHOR]

The aim of this study is to evaluate the feasibility of using lipid-accumulating microalgae to remove cephalosporin antibiotics 7-amino cephalosporanic acid (7-ACA) from wastewater with the additional benefit of biofuels production. Three isolated microalgal strains (namely, Chlorella sp. Cha-01, Chlamydomonas sp. Tai-03 and Mychonastes sp. YL-02) were cultivated under 7-ACA stress and their biomass productivity, lipid production and N-NO 3 − consumption were monitored. It was found that 7-ACA had slight inhibition effects on the microalgal growth at the ratio of 12.0% (Cha-01), 9.6% (YL-02), 11.7% (Tai-03). However, lipid accumulation in the three microalgae was not influenced by the presence of 7-ACA. The investigation on the 7-ACA removal mechanisms during microalgal growth shows that 7-ACA was mainly removed by microalgae adsorption as well as hydrolysis and photolysis reactions. This study demonstrates that using microalgae to treat antibiotic-containing wastewater is promising due to the potential of simultaneous antibiotic removal and biofuel production. [ABSTRACT FROM AUTHOR]

The effects of light-emitting diode (LED) wavelength, light intensity, nitrate concentration, and time of exposure to different LED wavelength stresses in a two-phase culture on lipid production were evaluated in the microalga, Picochlorum atomus . The biomass produced by red LED light was higher than that produced by purple, blue, green, or yellow LED and fluorescent lights from first phase of two-phase culture. The highest lipid production of P. atomus was 50.3% (w/w) with green LED light at 2 days of second phase as light stress. Fatty acid analysis of the microalgae showed that palmitic acid (C16:0) and linolenic acid (C18:3) accounted for 84–88% (w/w) of total fatty acids from P. atomus . The two-phase culture of P. atomus is suitable for biofuel production due to higher lipid productivity and favorable fatty acid composition. [ABSTRACT FROM AUTHOR]

Coelastrella sp. QY01, a microalgae species isolated from a local pond, was identified and used for the treatment of anaerobically and aerobically treated swine wastewater (AnATSW). Microalgal growth characteristics, nutrient removal and lipid accumulation of QY01 cultivated in the initial concentration of AnATSW ranged from 63 to 319 mg NH 3 -N/L were examined. The specific growth rate of QY01 cultivated in cultures ranged from 0.269 to 0.325 day −1 with a biomass productivity from 42.77 to 57.46 mg L −1 day −1 . Removal rates for NH 3 -N, TP and inorganic carbon in AnATSW at the various nutrient concentrations ranged from 90% to 100%, from 90% to 100% and from 74% to 78%, respectively. The lipid content of QY01 ranged from 22.4% to 24.8%. The lipid productivity was positive correlation with the biomass productivity. 40% AnATSW was optimal for QY01 cultivation, in which nutrient removal and productivity of biomass and lipid were maximized. [ABSTRACT FROM AUTHOR]

A novel culture medium to enhance the biomass and lipid production simultaneously by Chlorella vulgaris UTEX 26 was designed in three stages of optimization. Initially, a culture medium was inferred applying the response surface method to adjust six factors [NaNO 3 , NH 4 HCO 3 , MgSO 4 ·7H 2 O, KH 2 PO 4 , K 2 HPO 4 and (NH 4 ) 2 HPO 4 ], which were selected on the basement of BBM (Bold’s Basal Medium) and HAMGM (Highly Assimilable Minimal Growth Medium) culture media. Afterwards, the nitrogen source compound was optimized to reduce both, ammonium and nitrate concentrations. As result of the optimization process, the proposed culture medium improved 40% the biomass (0.73 g L −1 ) compared with the BBM medium and 85% the lipid concentration (281 mg L −1 ), with respect to HAMGM medium. Some culture media components concentrations were reduced up to 50%. Gas chromatography analysis revealed that C16:0, C18:0, C18:1, C18:2 and C18:3 were the major fatty acids produced by C. vulgaris UTEX 26. [ABSTRACT FROM AUTHOR]

A two-step strategy comprising heterotrophic cultivation and photo-chemical modulator induction was developed to enhance biomass and lipid accumulation in the oleaginous Monoraphidium sp. QLY-1, which was isolated from Qilu Lake in Yunnan Plateau. The algae were first cultivated heterotrophically to achieve high biomass concentration (5.54 g L −1 ) with a lipid content of 22.47%. The cultivated algae were diluted, transferred to light environment, and treated with different chemical elicitors. Results showed that the lipid content increased to 36.68% after 3-day of photoinduction. The lipid content was further enhanced by 1.21, 1.32, and 1.29 folds in algal cells treated with nitrogen deficiency, 20 g L −1 NaCl, and 5 mM glycine betaine, respectively. The maximum lipid content (48.54%) and lipid productivity (121.27 mg L −1 d −1 ) were obtained in treatments with 20 g L −1 NaCl and 5 mM GB, respectively. This study proposes a strategy to efficiently produce lipids by using microalgae. [ABSTRACT FROM AUTHOR]

Despite the vast interest in microalgae as feedstock for biodiesel production, relatively few studies examined their response to diurnal temperature fluctuation. Here, we describe biomass and lipid productivities and fatty acid profiles of thermo-resistant Micractinium sp. and Scenedesmus sp. grown in batch cultures in a laboratory set-up that mimics a typically warm summer day in Central Anatolia with a 16-h light temperature of 30 °C and 8-h dark temperature of 16 °C (30 °C (day)/16 °C (night)). Both strains can survive a temperature range of 10–50 °C. We found the lipid productivities of Micractinium sp. and Scenedesmus sp. as 30/21 mg L −1 d −1 and 6/7 mg L −1 d −1 , respectively during the 30 °C (day)/16 °C (night) cycle. Saturated fatty acid content increased with increasing temperature. Additionally, we cultured Micractinium sp. under Nitrogen (N) and Phosphorus (P) limiting conditions. Highest lipid productivity of 85.4 ± 2 mg L −1 d −1 was obtained under P-depletion during exponential growth phase. Oleic acid amount also increased eight fold during P-deplete. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of carbohydrates ratios on Rhodosporidium toruloides -1588 was studied. • Hydrolysate to crude glycerol ratio of 60:40 resulted in 49% lipid accumulation. • Scale-up to bench scale fermenter led to 56.3% lipid accumulation in 50% less time. • Fatty acids can be used as feedstock for food, pharmaceutical, biofuel industries. • Wood hydrolysate and glycerol are sustainable alternative substrates. Wood hydrolysate has been regarded as sustainable and renewable substrate to produce microbial lipids, a potential feedstock for the biodiesel industry. Moreover, the major by-product of biofuel industries is crude glycerol but its implementation as a carbon source is still constrained due to the presence of impurities resulting in low biomass production and low lipid titer. Thus, this study investigates the effect of different carbon ratios of hydrolysate and crude glycerol on R. toruloides -1588. Hydrolysate to crude glycerol ratio of 60:40 resulted in maximum lipid accumulation of 49% (w/w), more than 90% of sugars and glycerol consumption. Further, scale-up to bench-scale fermenter resulted in 12% higher lipid accumulation (56.3% w/w , 0.15 g/L∙h) in 50% less time than flask fermentation. Hence, the ability of R. toruloides -1588 to flourish on different carbohydrates and accumulate high lipid content will be beneficial for the further development of biorefinery industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chlorella sorokiniana cultivation under photoautotrophic or heterotrophic conditions. • Higher lipids (3.19 ± 0.23 g/L) at C/N 60 after 72 h growth on heterotrophic mode. • Autotrophic cultivation favored proteins (416.66 mg/g CDW) & lutein (6.40 mg/g CDW) • Total Carbohydrates for photoautotrophic (6.39 %) and heterotrophic (8.66 %) modes. • The lipid profile was suitable for its application in biodiesel production. Biorefineries enable the circular, sustainable, and economic use of waste resources if value-added products can be recovered from all the generated fractions at a large-scale. In the present studies the comparison and assessment for the production of value-added compounds (e.g., proteins, lutein, and lipids) by the microalga Chlorella sorokiniana grown under photoautotrophic or heterotrophic conditions was performed. Photoautotrophic cultivation generated little biomass and lipids, but abundant proteins (416.66 mg/g CDW) and lutein (6.40 mg/g CDW). Heterotrophic conditions using spruce hydrolysate as a carbon source favored biomass (8.71 g/L at C/N 20 and 8.28 g/L at C/N 60) and lipid synthesis (2.79 g/L at C/N 20 and 3.61 g/L at C/N 60) after 72 h of cultivation. Therefore, heterotrophic cultivation of microalgae using spruce hydrolysate instead of glucose offers a suitable biorefinery concept at large-scale for biodiesel-grade lipids production, whereas photoautotrophic bioreactors are recommended for sustainable protein and lutein biosynthesis. [ABSTRACT FROM AUTHOR]

To improve the biomass yield and lipid productivity, two desert microalgae, Desmodesmus sp. S81 and G41 were induced mutagenesis by Ethylmethane sulfonate (EMS), and obtained two potential mutants, Desmodesmus sp. S5 and G3 from the mutagenic clones for their greatly promoted biomass and lipid production. The results showed that the biomass yield, lipid content and lipid productivity of the mutant strains S5 and G3 were 778.10 mg·L −1 , 48.41% and 19.83 mg·L −1 ·d −1 , 739.52 mg·L −1 , 46.01%, and 17.92 mg·L −1 ·d −1 , respectively, which presented the increment of 45.50%, 8.00% and 74.24%, 20.67%, 10.35% and 55.77% than those of S81 and G41. Comparing with the wild strains, the mutants showed reduced PUFAs and glycol lipids, elevated MUFAs and neutral lipids contents, which were appropriate for biodiesel production. [ABSTRACT FROM AUTHOR]

A culture medium based on NPK-10:26:26 fertilizer was formulated for enhanced biomass and lipid production of Dunaliella tertiolecta by selecting appropriate nutrients and environmental parameters. Five-level-five-factor central composite design assisted response surface methodology was adopted for optimal cultivation of D. tertiolecta and results were compared with simple genetic algorithm (GA). Significant improvement in biomass and lipid production was obtained using newly formulated fertilizer medium over f /2 medium. Following optimal parameters [i.e., NaHCO 3 , (mM), NPK-10:26:26 (g L −1 ), NaCl (M), light intensity (μmol m −2 s −1 ) and temperature (°C)] were obtained for maximum biomass (1.98 g L −1 ) and lipid production (0.76 g L −1 ): (42.50, 0.33, 1.09, 125, 25.13) and (38.44, 0.40, 1.25, 125, 24.5), respectively using GA. A multi-objective optimization was solved using non-dominated sorting GA to find best operating variables to maximize biomass and lipid production simultaneously. Effects of operating parameters and their interactions on algae and lipid productivity were successfully revealed. [ABSTRACT FROM AUTHOR]

The development of a culture system for Chlorella sp. GD to efficiently produce biomass and oil for biodiesel production was investigated. Chlorella sp. GD was cultivated with 0%, 25%, 50%, 75% and 100% piggery wastewater (diluted by medium) at 300 μmol m −2 s −1 , a 2% CO 2 aeration rate of 0.2 vvm and 26 ± 1 °C; after a 10-day culture in batch cultures, the maximum specific growth rate and biomass productivity of the microalga obtained in 100% piggery wastewater were 0.839 d −1 and 0.681 g L −1 d −1 , respectively. The highest lipid content and lipid productivity were 29.3% and 0.155 g L −1 d −1 at 25% wastewater, respectively. In semi-continuous cultures, the biomass and lipid productivities with 25–75% wastewater ratios were greater than 0.852 and 0.128 g L −1 d −1 , respectively. These results show that Chlorella sp. GD grows efficiently in piggery wastewater, and that a stable growth performance was achieved for long-term microalgal cultivation in a semi-continuous culture. [ABSTRACT FROM AUTHOR]

This work investigated a top-lit open microalgae bioreactor that uses a gas-lift system to enable deeper production depths, thereby significantly reducing the footprint. Growth of Scenedesmus sp. in a one-meter deep system by sparged with 6% CO 2 -enhanced air was evaluated. The results gave comparable volumetric biomass productivity (0.06 g dw L −1 day −1 ), but around three-times higher areal productivity (60.0 g dw m − 2 day − 1 ) than reported for traditional raceways. The lipid content of the Scenedesmus sp. was increased by 27% with an enhanced level of CO 2 in the sparging gas. [ABSTRACT FROM AUTHOR]

Two fresh water microalgae, Coelastrella sp. M-60 and Micractinium sp. M-13 were investigated in this study for their potential of biodiesel production. For increasing biomass and lipid production, these microalgae were subjected to nutrient starvation (nitrogen, phosphorous, iron), salinity stress and nutrient supplementation with sugarcane industry effluent, citric acid, glucose and vitamin B 12 . The lipid productivity obtained from the isolates Coelastrella sp. M-60 (13.9 ± 0.4 mg/L/day) and Micractinium sp. M-13 (11.1 ± 0.2 mg/L/day) was maximum in salinity stress. The media supplemented with all the four nutrients yielded higher lipid productivity than the control. The response surface methodology (RSM) was employed to evaluate the effect of sugarcane industry effluent and citric acid on growth and lipid yield. Fatty acid profile of Coelastrella sp. M-60 and Micractinium sp. M-13 were composed of C-14, C-16:0, C-18:0, C-18:1 and C-18:2 and their fuel properties were also in accordance with international standards. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biomass production of microalgae in river water as a medium. • Microalgae removed a high rate of organic and inorganic pollutants. • FAME derived from biomass showed suitable applications as feed and green fuel. • River water phycoremediation is essential for a healthy environment. The present study evaluated polluted river water as a medium for the growth of oleaginous microalgae under mixotrophic conditions. Microalgae grow in the medium and produce biomass, pigments, and lipids with the removal of pollution loads from wastewater. Selenastrum sp. SL7 produced maximum biomass and lipids of 660 mg L-1 and 194.5 mg L-1, respectively. Fatty acid profiling data showed that elevated saturated fatty acid production and major fatty acids found in lipid from these algae were palmitic acids, oleic acid, stearic acid, linolenic acid, and linoleic acid. The low percentage of polyunsaturated fatty acids of EPA was also detected. Water quality in terms of pH, DO, TDS, COD, and BOD was significantly improved. The use of this medium for microalgae cultivation not only improves the biomass and lipid yields but also serves as an excellent means of phycoremediation of pollutants in waste streams with value addition and environmental benefits. [ABSTRACT FROM AUTHOR]

In this research, a two-stage process consisting of cultivation in nutrient rich and nitrogen starvation conditions was employed to enhance lipid production in Chlorella vulgaris algal biomass. The effect of supplying different organic and inorganic carbon sources on cultivation behavior was investigated. During nutrient sufficient condition (stage I), the highest biomass productivity of 0.158 ± 0.011 g/L/d was achieved by using sodium bicarbonate followed by 0.130 ± 0.013, 0.111 ± 0.005 and 0.098 ± 0.003 g/L/d for sodium acetate, carbon dioxide and molasses, respectively. Cultivation under nitrogen starvation process (stage II) indicated that the lipid and fatty acid content increased continuously to a maximum value at day 2. Using carbon dioxide resulted in highest cell density, while using sodium acetate led to the highest fatty acid content. Molasses was not as effective as other carbon sources, but by taking into account its lower price, it can be considered as a suitable carbon source for algal lipid productivity. [ABSTRACT FROM AUTHOR]

Nannochloropsis has emerged as a promising alga for biodiesel production. However, the genus consists of 6 species and hundreds of strains making strain selection a challenge. Furthermore, oil productivity is instrumental to economic viability of any algal strain for industrial production, which is dependent on growth rate and oil content. In most cases, these two parameters have been studied independently. Thus, the goal of this study is to provide a combined method for evaluating strain performance in specially designed photobioreactors together with an in-depth lipidomic analyses. The nine strains of Nannochloropsis tested showed considerable variations in productivity and lipidomics highlighting the importance of strain selection. Finally, Nannochloropsis gaditana CCMP527 and Nannochloropsis salina CCMP537 emerged as the two most promising strains, with an oil content of 37 and 27 dry wt% after 11-day nitrogen starvation, respectively, resulting in TAG productivity of 13 × 10 −3 and 18 × 10 −3 kg m −3 d −1 , respectively. [ABSTRACT FROM AUTHOR]

The study explores on upstream and downstream process in Microcystis aeruginosa for biodiesel production. The alga was isolated from temple tank, acclimatized and successfully mass cultivated in open raceway pond at semi-continuous mode. A two step combined process was designed and harvested 99.3% of biomass, the daily dry biomass productivity was recorded up to 28 g m –2 day −1 . The lipid extraction was optimized and achieved 21.3%; physicochemical properties were characterized and found 11.7% of FFA, iodine value 72% and 99.2% of ester content. The lipid was transesterified by a two step simultaneous process and produced 90.1% of biodiesel; the calorific value of the biodiesel was 38.8 MJ/kg. Further, the physicochemical properties of biodiesel was characterized and found to be within the limits of American ASTM D6751. Based on the areal and volumetric biomass productivity estimation, M. aeruginosa can yield 84.1 tons of dry biomass ha −1 year −1 . [ABSTRACT FROM AUTHOR]

[Display omitted] • Marine diatom C. gracilis exhibits growth in presence of contaminant estradiol. • Treated cultures showed higher biomass productivity and increase in cell number. • Enhanced production of bound and soluble exopolysaccharides at stationary phase. • Increment in carotenoids, protein and fucoxanthin than control. In the recent past, the presence of steroid hormones in marine bodies has led to the eruption of endocrine - disrupting molecules which have detrimental effects on aquatic life. However, the resilience and robustness of diatoms to adsorb and grow under the multitude of nutrient stress allow them to utilize the plethora of such compounds. Hence, in this study, we have implemented this unique ability of diatoms to sustain on simulated steroidal wastewater made of estradiol pills and analyze their corresponding impact on growth, biomass production, and lipid synthesis. We hereby report that with an increasing concentration of estradiol (0.5–2.0 mg L−1) there was an increment in cell numbers, and a 1.5-fold increase in the dry cell weight and lipid content (up to 29.5% DW). Thus, culturing Chaetoceros gracilis in the optimized media had a significant impact on biomass productivity which could further promote the untapped potential of diatoms. [ABSTRACT FROM AUTHOR]

[Display omitted] • BGW can be used as a culture medium for Spirulina (BGWS) and Chlorella (BGWC). • BGWS/BGWC is an innovative cultivation strategy for Spirulina and Chlorella growth. • BGWS condition resulted in higher Spirulina carbohydrate productivity. • BGWC condition resulted in higher Chlorella lipid productivity. Brackish groundwater is promising for the cultivation of economically important microalgae; however, its effects have been evaluated only after nutrient supplementation. In this study, 100% brackish groundwater was evaluated as a culture medium for Spirulina sp. (BGWS) and Chlorella fusca (BGWC). In addition, the effects of supplementation with 25% of the nutrients from Zarrouk (BGWS25) and BG-11 (BGWC25) culture media were evaluated. BGWS and BGWC increased the concentration (68.1% w w−1) and productivity of carbohydrate (35.3 mg L−1 d−1) in Spirulina sp. and increased the concentration (56.4% w w−1) and productivity (13.5 mg L−1 d−1) of lipids in C. fusca biomass, when compared to that in the respective controls. The use of brackish groundwater as the sole culture medium is an innovative alternative for the economic production of biomass rich in carbohydrates and lipids. This has potential applications for biofuel production. [ABSTRACT FROM AUTHOR]

Highlights: [•] Strain PD630 can tolerate low concentration of five model inhibitory compounds. [•] Strain PD630 can use vanillic acid and TPCA for cell growth and TAG accumulation. [•] Vanillin can be used as a carbon source, but TAGs are not accumulated. [•] Strain PD630 can grow on three lignocellulosic hydrolysates and accumulate TAGs. [Copyright &y& Elsevier]

Highlights: [•] Marine diatom Chaetoceros muelleri grow well under high CO2 levels (10–20%). [•] The highest biomass, total and neutral lipid contents were all found under 10% CO2. [•] Total lipid content is 43.40% DW under 10% CO2 with highest biomass productivity. [•] Fatty acid composition of C. muelleri is very ideal for biofuels production. [•] C. muelleri have great potential to biodiesel produce using the flue gases. [Copyright &y& Elsevier]

Highlights: [•] SMP for whole microalgae were better than lipid-extracted microalgae residues. [•] The control of I/S ratio during BMP could overcome pH drop and LCFA inhibition. [•] No signs of VFA or ammonia inhibition occurred when digested at I/S⩾1.0 ratio. [•] Higher methane production was not related to species but to lipid content of biomass. [Copyright &y& Elsevier]

Harvest water recycling for Chlorella zofingiensis re-cultivation under nutrient limitation was investigated. Using 100% harvest water, four cultures were prepared: Full medium, P-limited medium, N-limited medium and N- and P-limited medium, while another full medium was also prepared using 50% harvest water. The results showed that the specific growth rate and biomass productivity ranged from 0.289 to 0.403 day −1 and 86.30 to 266.66 mg L −1 day −1 , respectively. Nutrient-limited cultures witnessed much higher lipid content (41.21–46.21% of dry weight) than nutrient-full cultures (26% of dry weight). The N- and P-limited medium observed the highest FAME yield at 10.95% of dry weight, while the N-limited culture and P-limited culture shared the highest biodiesel productivity at 20.66 and 19.91 mg L −1 day −1 , respectively. The experiment on harvest water recycling times demonstrated that 100% of the harvest water could be recycled twice with the addition of sufficient nutrients. [ABSTRACT FROM AUTHOR]

The potential use of Synechocystis sp. PCC6803 ( Synechocystis sp.) for lipid production using artificial seawater (ASW) medium supplemented with anaerobic digestion effluent (ADE) was investigated and compared to marine microalgae, Nannochloropsis salina ( N. salina ). Synechocystis sp. showed growth rates 83% and 20% higher than N. salina at 3% and 6% ADE loading ratios, respectively, achieving the highest biomass productivity of 212 mg L −1 d −1 in semi-continuous cultivation. The rapid growth of Synechocystis sp. was offset by its low lipid content, resulting in lipid productivities 7–28% lower than N. salina . The lipid productivity of Synechocystis sp. may be further improved by decreasing the harvesting interval during semi-continuous cultivation. Fatty acid analysis showed that lipids extracted from Synechocystis sp. contained higher palmitic acid (60.3 ± 2.0%) and linoleic acid (20.0 ± 1.6%), and had a higher cetane number and oxidative stability than those from N. salina . [ABSTRACT FROM AUTHOR]

In this study, Scenedesmus obtusus XJ-15 was firstly selected from seven strains microalgae (Chlorophyta, Scenedesmaceae ) and then cultivated using a two-stage strategy, which composed of fast cell growth in stage I and followed by lipid induction in stage II in 5-L flasks outdoors. In stage I, the biomass productivity was increased from 139.4 to 212.1 mg L −1 d −1 . In stage II, lipid content was increased from 26.1% to 47.7% by adding NaCl into the culture. This two-stage process was also realized in an 140-L photobioreactor outdoors, with a biomass productivity of 86.5 mg L −1 d −1 and CO 2 fixation rate of 170.0 mg L −1 d −1 in the first stage, and high lipid content of 42.1% in the second stage. With such a culture strategy, the overall lipid productivity was improved and better biodiesel quality was obtained. These results suggested the photoautotrophic two-stage system was not only feasible but also effective. [ABSTRACT FROM AUTHOR]

[Display omitted] • Algal drying characteristics of convective hot air and microwave oven were discussed. • Microwave drying is faster with relatively lower specific energy requirements. • Convective and microwave drying followed thin layer drying models. • 14.4% higher lipid content was obtained in microwave dried algal biomass. • Uniform volumetric heating in microwave drying preserves biochemical content. Conventional microalgal drying consumes huge time and contributes to 60–80% of downstream process costs. With the aim to develop an effective and rapid drying process, the present study evaluated the performance of microwave based drying (MWD) with a power range of 360–900 W and compared with the conventional oven drying (OD) at 40–100 °C. MWD was found to be efficient due to uniform and volumetric heating because of dipolar interaction, with an effective diffusivity of 0.47 × 10−9−1.63 × 10−9 m2 s−1, comparatively higher than OD. Activation and specific energy of 32.43 W g−1 and 42.9–56.07 kWh kg−1 was projected respectively, and a falling rate period with best fit for Newton and Henderson-Pabis model was observed for MWD. Uniform heating from internal sub-surface avoided cell distress, resulting in 14.4% higher lipid yield and significant preservation of biochemical components that can be processed into bioenergy and valuable products in microalgal biorefinery. [ABSTRACT FROM AUTHOR]

[Display omitted] • Actinomycete co-culture successfully enhanced both microalgal biomass and lipid. • Piscicocus intestinalis WA3 produced high algal growth-promoting agents. • Microbial lipids are composed of C16-C20 fatty acids with good fuel properties. • Biogas effluent can be used as cost-effective media for actinomycete co-culture. In this study, an innovative approach to enhance the production of microalgal biomass and lipid as a promising sustainable feedstock for biodiesel was proposed using an actinomycetes co-culture with microalgae in the biogas digestate effluent (BDE) that can be employed as an environmentally friendly and cost-effective strategy. Among tested actinomycete isolates, Piscicocus intestinalis WA3 produced indole-3-acetic acid and siderophores as algal growth promoting agents and showed effective lipid accumulation with satisfying fatty acids composition. During co-cultivation of P. intestinalis WA3 with microalga Tetradesmus obliquus AARL G022 in the BDE, biomass production, chlorophyll a content, and lipid productivity were significantly increased by 1.30 folds, 1.39 folds, and 1.55 folds, respectively, compared to microalgae monoculture. The accumulated lipids contained long-chain fatty acids with better fuel properties that could potentially be used as biodiesel feedstock. The overall results evidenced that actinomycete co-culture would contribute greatly to the cost-effective production of environmental-friendly microbial-based biofuel. [ABSTRACT FROM AUTHOR]

Highlights: [•] Heavy ion irradiation mutagenesis was firstly applied in microalgae breeding. [•] The mutant HP-1 showed higher biomass production than the wild type Nannochloropsis. [•] Its lipid productivity was increased by 28% compared to the wild type. [•] The reason caused its higher biomass accumulation and lipid productivity was studied. [•] Further, its TAG content was higher and polar lipid was lower than the wild type. [Copyright &y& Elsevier]

Highlights: [•] Microalgae base oil production was analyzed as a potential biodiesel feedstock. [•] Different harvesting and solvent lipid extraction pathways were evaluated. [•] It is of capital importance to reduce the investment of the cultivation process. [•] Biomass production (cultivation/harvesting) is responsible of 65% of the total cost. [•] The required biodiesel price must be around $6000 per MT to have a feasible process. [Copyright &y& Elsevier]

Abstract: Microalgae are a promising source for proteins, lipids and carbohydrates for the food/feed and biofuel industry. In comparison with soya and palm oil, microalgae can be grown in a more efficient and sustainable way. To make microalgae production economically feasible it is necessary to optimally use all produced compounds. To accomplish this focus needs to be put on biorefinery techniques which are mild and effective. Of the techniques described, Pulsed Electric Field (PEF) seems to be the most developed technique compared to other cell disruption applications. For separation technology ionic liquids seems most promising as they are able to both separate hydrophobic and hydrophilic compounds. But additional studies need to be evolved in the coming years to investigate their relevance as novel cell disruption and separation methods. We propose a complete downstream processing flow diagram that is promising in terms of low energy use and state of the art knowledge. [Copyright &y& Elsevier]

Abstract: A cultivation system in the two-stage photoautotrophic–photoheterotrophic/mixotrophic mode was adapted to maximize lipid productivity of two freshwater strains of Chlorella sp. grown in brewery wastewater (BWW). The endogenous Chlorella sp. isolated from BWW had a higher growth rate than wild-type Chlorella vulgaris (UTEX-265) while C. vulgaris (UTEX-265) had a higher maximal biomass and lipid contents than that of endogenous Chlorella sp., resulting in more than 90% of the inorganic nutrients in both total nitrogen (TN) and phosphorus (TP) was removed during the first stage in the two-stage photoautotrophic–photoheterotrophic mode in each Chlorella sp. The maximal biomass and lipid contents of C. vulgaris (UTEX-265) for single stage photoautotrophic cultivation were 1.5g/L and 18%, respectively. Importantly, during two-stage photoautotrophic–photoheterotrophic cultivation for C. vulgaris (UTEX-265), the biomass was increased to 3.5g/L, and the lipid productivity was increased from 31.1 to 108.0mg/Lday. [Copyright &y& Elsevier]

Abstract: For outdoor culture with light–dark cycle, the biomass and lipid losing at night resulted in lowering the biomass and lipid productivity. Previous studies focused on the contents of carbohydrate and protein in response to temperature for production of animal feed and nutritional supplements. In this study, the effects of temperature on the variations of biomass concentration, lipid content and fatty acids composition for production of biofuels were investigated under a light–dark cyclic culture. The results showed that 30°C was the optimal daytime temperature for achieving high biomass and lipid; raising daytime temperature can lessen night biomass loss and stimulate lipid accumulation. Subsequently, outdoor culture strategy has been improved: keeping culture broth no less than 30°C during the daytime. Consequently, the net biomass and lipid productivity were increased by 37.8% and 44.9% when compared to the former culture process in the same outdoor climatic conditions. [Copyright &y& Elsevier]

Abstract: Chemo-enzymatic saccharification and bioethanol fermentation of the residual biomass of Dunaliella tertiolecta after lipid extraction for biodiesel production were investigated. HCl-catalyzed saccharification of the residual biomass at 121°C for 15min produced reducing sugars with a yield of 29.5% (w/w) based on the residual biomass dry weight. Various enzymes were evaluated for their ability to saccharify the residual biomass. Enzymatic saccharification using AMG 300L produced 21.0mg/mL of reducing sugar with a yield of 42.0% (w/w) based on the residual biomass at pH 5.5 and 55°C. Bioethanol was produced from the enzymatic saccharification products without additional pretreatment by Saccharomyces cerevisiae with yields of 0.14g ethanol/g residual biomass and 0.44g ethanol/g glucose produced from the residual biomass. The waste residual biomass generated during microalgal biodiesel production could be used for the production of bioethanol to improve the economic feasibility of microalgal biorefinery. [Copyright &y& Elsevier]

Abstract: To address the large energy consumption of microalgae dewatering and to simplify the conventional two-step method (cellular lipid extraction and lipid transesterification) for biodiesel production, a novel process for the direct conversion of wet microalgae biomass into biodiesel by microwave irradiation is proposed. The influences of conventional thermal heating and microwave irradiation on biodiesel production from wet microalgae biomass were investigated. The effects of using the one-step (simultaneous lipid extraction and transesterification) and two-step methods were also studied. Approximately 77.5% of the wet microalgal cell walls were disrupted under microwave irradiation. The biodiesel production rate and yield from wet microalgae biomass obtained through the one-step process using microwave irradiation were 6-fold and 1.3-fold higher than those from wet microalgae obtained through the two-step process using conventional heating. [Copyright &y& Elsevier]

Abstract: Anaerobic digestion of algal biomass will be an essential component of algal biofuel production systems, yet the methane yield from digestion of algae is typically much lower than the theoretical potential. In this work, high pressure thermal hydrolysis (HPTH) is shown to enhance methane yield during algae digestion. HPTH pre-treatment was applied to both raw algae and algal residue resulting from lipid extraction. HPTH and even the lipid extraction process itself increased methane yield, by 81% and 33% respectively; in combination they increased yield by 110% over that of the raw algae (18L CH4 gVS−1 substrate). HPTH had little effect on the rate of anaerobic digestion, however lipid extraction enhanced it by 33% over that for raw algae (0.21day−1). Digestion resulted in solubilisation of nitrogen (and phosphorous to a lesser degree) in all cases, showing that there is potential for nutrient recycling for algal growth. [Copyright &y& Elsevier]

Abstract: A green microalgae, named as Ettlia texensis was obtained from local freshwater in Turkey. The effects of autotrophic, photoheterotrophic and heterotrophic cultivations on biomass and lipid production were studied. Searching the preferences of the carbon and nitrogen source revealed that this strain could grow photoheterotrophically well with glucose and yeast extract. In the optimized medium, the highest biomass productivity and total lipid content achieved were 0.97g/Ld and 26% of dry weight basis, respectively. Moreover, the major fatty acid methyl esters were C16:0; C18:1; C18:2 and C18:3. In a scale-up attempt, productions were accomplished in a 3L stirred tank bioreactor. The final biomass and lipid productivities obtained in bioreactor with 250rpm agitation rate were 0.92g/Ld and 322mg/Ld, respectively. The biochemical compositions were monitored simultaneously by the FTIR spectroscopy during the production in bioreactor. E. texensis could be potent candidate for commercial production in the bioreactor photoheterotrophically. [Copyright &y& Elsevier]

Abstract: To augment biomass and lipid productivities of heterotrophic cultured microalgae Chlorella sorokiniana, the influence of environmental temperature and medium factors, such as carbon source, nitrogen source, and their initial concentrations was investigated in this study. The microalga C. sorokiniana could tolerate up to 42°C and showed the highest growth rate of 1.60d−1 at 37°C. The maximum dry cell weight (DCW) and corresponding lipid concentration was obtained with 80gL−1 of initial glucose and 4gL−1 of initial KNO3 at 37°C. In 5-L batch fermentation, the DCW increased dramatically from 0.9gL−1 to 37.6gL−1 in the first 72h cultivation, with the DCW productivity of 12.2gL−1 d−1. The maximum lipid content of 31.5% was achieved in 96h and the lipid productivity was 2.9gL−1 d−1. The results showed C. sorokiniana could be a promising strain for biofuel production. [Copyright &y& Elsevier]

Abstract: Over 100 green-colored colonies were isolated from environmental samples when cultivating on a BG11 agar medium, and 4 strains showing different morphologies were selected based on light microscopic observation. Among these strains, the microalgal species with the highest growth rate under 10% CO2 was identified as Ettlia sp. YC001 using an 18S rDNA-based phylogenetic analysis and morphological comparison. The highest cell density of 3.10g/L (based on dry cell weight) and biomass productivity of 0.19g/L/d were obtained under 5% CO2 after 16days. The lipid content and productivity were also up to 42% of the dry cell weight and 80.0mg/L/d, respectively. The color of the Ettlia sp. YC001 culture changed from green to red after a month due to the accumulation of certain carotenoids. Therefore, it would seem that Ettlia sp. YC001 is appropriate for mitigating CO2 due to its high biomass productivity, and a suitable candidate for producing biodiesel and high-value products. [Copyright &y& Elsevier]

Abstract: In this study, an inulinase-producing yeast strain Pcla22 of Pichia guilliermondii was identified. It was found that the yeast strain Pcla22 could produce higher amount of oil and more lipid bodies in its cells than any other yeast strains tested in this study. Under the optimal conditions, 60.6%(w/w) of lipid based on cell dry weight, 20.4g/l of the dry cell mass, SCO produced per g of consumed sugar of 0.19g/g and biomass produced per g of consumed sugar of 0.32g/g were obtained in the culture of the yeast strain Pcla22 after 96h of the fed-batch fermentation. Over 79.8% of the fatty acids from the yeast strain Pcla22 grown in the oil production medium containing inulin was C16:0 and C18:1, especially C18:1 (57.9%). The biodiesel obtained from the produced lipid could be burnt well. [Copyright &y& Elsevier]

Abstract: Microalgae-derived lipids are an alternative to vegetable and fossil oils, but lipid content and quality vary among microalgae strains. Selection of a suitable strain for lipid production is therefore of paramount importance. Based on published results for 96 species, nine strains were selected to study their biomass, total fatty acid, and triacylglycerol (TAG) production under nitrogen-sufficient and deficient cultivation conditions. Under nitrogen-deficient conditions, Chlorella vulgaris, Chlorella zofingiensis, Neochloris oleoabundans, and Scenedesmus obliquus, accumulated more than 35% of their dry weight as TAGs. Palmitic and oleic acid were the major fatty acids produced. The main difference between these strains was the amount of biomass that was produced (3.0–7.8-fold increase in dry weight) and the duration that the biomass productivity was retained (2–7days) after nitrogen depletion. S. obliquus (UTEX 393) and C. zofingiensis (UTEX B32) showed the highest average TAG productivity (322 and 243mgl−1 day−1). [Copyright &y& Elsevier]

Abstract: High-cost downstream process is a major bottleneck for producing microalgal biodiesel at reasonable price. Conventional lipid extraction process necessitates biomass drying process, which requires substantial amount of energy. In this regard, lipid extraction from wet biomass must be an attractive solution. However, it is almost impossible to recover lipid directly from wet microalgae with current technology. In this study, we conceived osmotic shock treatment as a novel method to extract lipid efficiently. Osmotic shock treatment was applied directly to wet Chlamydomonas reinhardtii biomass with water content >99%, along with both polar and non-polar organic solvents. Our results demonstrated that osmotic shock could increase lipid recovery approximately 2 times. We also investigated whether the presence of cell wall or different cell stages could have any impact on lipid recovery. Cell wall-less mutant stains and senescent cell phase could display significantly increased lipid recovery. Taken together, our results suggested that osmotic shock is a promising technique for wet lipid extraction from microalgal biomass and successfully determined that specific manipulation of biomass in certain cell phase could enhance lipid recovery further. [Copyright &y& Elsevier]