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[Display omitted] • Microalga and free feeds degraded in percentages of 1.5 and 24% respectively. • No antioxidant treatment is necessary for feed storage during 1.5 year period. • First time evaluated the price of microalgae feeds in a viable manner. The rising prices of fishery derivatives limits their use in aquafeeds. Therefore, other alternatives are used to replace those ingredients. Among them, microalgae are of great interest both as an ingredient and as a potential stabilising agent against lipid oxidation. This study evaluates on the use of Nannochloropsis gaditana to prevent lipid oxidation in a set of 12 aquafeeds over 540 days of storage. Aquafeeds were formulated with/without 15 % N. gaditana combined with two antioxidants −butylhydroxytoluene (25–150 mg·kg-1) or vitamin E (500–3000 mg·kg-1). The effect of i) storage period, ii) presence of microalgae and iii) antioxidant addition on lipid oxidation was assessed. Results showed higher fatty acid degradation in diets lacking microalgae. The microalgae supplemented diets is enough for preserving feeds presenting the highest antioxidant effect at the end, without significant differences with the microalgae-supplemented feeds and those including antioxidants after 540 days of storage. [ABSTRACT FROM AUTHOR]

[Display omitted] • 20 K-lux light/3x-nutrients exhibited max. astaxanthin 54.4 mg/L by C. zofingiensis. • 4–8 K-lux successive light increase and 5% CO 2 exhibited the best biomass yield. • The maximum lipid 37% accumulation was obtained at 5% CO 2 and 20 k-lux light. • 20 K-lux light/3x-nutrients exhibited max. astaxanthin content 16.7 mg/g DCW. • Two-stage designed bioprocess boosts astaxanthin yield of C. zofingiensis. Microalgal astaxanthin possesses numerous bioactivities and has several health applications. The current research focuses on designing and optimizing the two-stage mixotrophic bioprocess by Chlorella zofingiensis for astaxanthin production. Gradual increase in light intensity (4-8k-lux) and 3x micronutrient concentration were the key parameters for maximizing biomass yield of 2.5 g/L during 15 days of stage I. Furthermore, stress conditions (excessive CO 2, light, salinity, etc.) enhanced astaxanthin yield at stage II. 20k lux light, 3x nutrients, and 5% CO 2 were the best ranges for maximum astaxanthin production. Maximum biomass yield and astaxanthin content were 3.3 g/L and 16.7 mg/g, respectively, after 29 days of bioprocess. Astaxanthin biosynthesis was also affected by salinity, but less than other parameters. Astaxanthin bioprocess resulted in enhanced lipid yields of 35–37%, which could be used for biodiesel. This study shows promising scale-up potential with attractive sustainability features of Chlorella zofingiensis model for commercial astaxanthin-lipid biorefinery. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3x-nutrients resulted in maximum lutein 71.13 mg/L from Chlorella sorokiniana C16. • 10 k lux light exhibited the best microalgae growth, biomass, and lutein yields. • The maximum 27% lipid accumulation was obtained at 75% salinity. • 32 °C temperature was determined for the maximum lutein content 17.4 mg/g DCW. • Two-stage optimized bioprocess boosts lutein production with minimal biomass loss. The current work aims to isolate high lutein-producing microalgae and maximize lutein production under a sustainable lutein-lipid biorefinery scheme. Lutein reduces retinitis, macular degeneration risk and improves eye health. An effective bioprocess design optimized nutrients, temperature, light, and salinity for biomass and lutein yield enhancement. 3X macro/micronutrients maximally enhanced biomass and lutein yields, 5.2 g/Land 71.13 mg/L. Temperature 32 °C exhibited maximum 17.4 mg/g lutein content and 10 k lux was most favorable for growth and lutein yield (15.47 mg/g). A 25% seawater addition led maximum of 21–27% lipid that could be used for biodiesel. Isolate was identified as Chlorella sorokiniana C16, which exhibited one of the highest lutein yields reported among recent studies, positioning it as a promising candidate for commercial lutein production. This study provides valuable insights into an effective bioprocess design and highlights the C16 strain potential as a sustainable platform for high-value lutein production under a biorefinery scheme. [ABSTRACT FROM AUTHOR]

Highlights • A mixotrophic microalgae Chlorella sp. G-9 was separated from a WWTP. • Increasing TOC/TN ratio of wastewater promoted algal growth and nutrient removal. • Growth rate of microalgae did not increase as TOC/TN ratio increased from 24 to 30. • 99.58% and 99.61% nitrogen was removed in the wastewaters with TOC/TN of 24 and 30. • The highest lipid content of 36.5% was achieved in wastewater with TOC/TN of 30. Abstract This study investigated the biomass/lipid production, nutrient removal and fatty acid composition of an isolated mixotrophic microalga (Chlorella sp. G-9) cultured in simulated wastewater with different TOC/TN ratio. As the TOC/TN ratio of wastewater increased from 0 to 24, the growth rate of Chlorella sp. G-9 increased gradually, but did not increase further at 30. Nutrient removal was related to microalgae growth. In the wastewater with TOC/TN ratio of 24 and 30, 99.58% and 99.61% nitrogen was removed, respectively. In conditions of initial TOC/TN ratios of 24 and 30, Chlorella sp. G-9 could accumulate lipid as high as 35.3% and 36.5%, respectively. The corresponding lipid productivities were 34.2 and 32.6 mg L−1 d−1, respectively, which were 13.7 and 13.0 times higher than those in photoautotrophic condition. Increasing the initial TOC/TN ratio of the wastewater could slightly increase the saturated degree in fatty acid, thereby improving the stability of biodiesel. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A SM-PBR was constructed for nutrients recovery from LL and lipids production. • The membrane module can protect microalgae cells from LL contamination. • Excess phosphate feeding increased lipid content but decreased biomass production. • N recovery and lipids production were boosted in the SM-PBR than traditional PBR. Abstract The aim of this work was to realize high-efficiency nutrients recovery from landfill leachate (LL) for microalgal lipids production. Negative effects of LL on microalgal lipid synthesis was revealed and a scalable membrane-based tubular photobioreactor (SM-PBR) was proposed to offset these negative effects. Microalgal biomass concentration was improved from 0 g/L in the traditional PBR to 2.13 g/L in the SM-PBR. Major operating conditions were optimized to enhance nutrients recovery and lipid productivity. The maximum N recovery efficiency of 74.31% and the maximum daily lipid production of 404.98 mg/d were obtained under the volume ratio of 5:3 (microalgae culture/LL stream) and phosphate feeding concentration of 50 mg/L. The obtained lipid was convinced to have a good combustion and anti-degradation property, with high cetane number (>52%) and low linolenic acid content (<12%). The SM-PBR provided a feasible approach for large-scale microalgal lipid production with LL. [ABSTRACT FROM AUTHOR]

Highlights • Protein recovery by pH-shift from a consortium microalgae-bacteria biomass. • ANOVA of NaOH concentration, temperature and time effect on process parameters. • Intermediate alkaline concentration (0.5 M NaOH) provided maxima extraction yields. • High solubilisation by alkaline hydrolysis but low acidic precipitation efficiency. • Co-extraction of lipids increased with process intensity. Abstract The influence of three variables on key parameters of the protein extraction process (an alkaline hydrolysis followed by an acidic precipitation) for biomass from innovative photo-bioreactors for pig manure treatment was evaluated. Alkaline hydrolysis provided high solubilisation values (up to 66.5% of the biomass), augmenting with increasing values of the three studied variables (NaOH concentration, temperature and time). Nevertheless, moderate total (13.2%) and protein extraction yields (16.9%) were obtained, which was attributable to protein denaturation or to the low effectivity of the precipitation method. Extracts rich in proteins (53.5%–77.9%) with suitable amino acid profiles were obtained, but significant amounts of the initial lipids (up to 44.6%) were co-extracted probably due to fatty acids saponification. These results establish the first step for future studies in enhancing cell wall disruption and protein recovery by coupling alkaline hydrolysis with other mechanical pre-treatments, while considering alternative separation and purification methods. [ABSTRACT FROM AUTHOR]

Highlights • Ultrasonic irradiation markedly enhanced the algal biomass and lipid accumulation. • The optimal ultrasonic treatment parameters for lipid production were obtained. • Low-strength ultrasonic stimulation did not damage the integrity of cell structure. • The biomass concentration and lipid content of microalgae increased 26.9% and 37%. Abstract Ultrasonic treatment was applied to enhance the biomass and lipid accumulation of mixotrophic microalgae. The optimal microalgal ultrasonic power, ultrasonic frequency, ultrasonic interval and growth phase were 20 W, 20 Hz, 2 s and logarithmic phase, respectively. The maximum biomass concentration and lipid content reached 2.78 g L−1 and 28.5%, which were 26.9% and 37% higher than those of the control group. Microscope analysis shows that ultrasonic exposure caused tiny cracks or holes on the surface of cell walls, but did not damage the integrity of algal cell structure. After ultrasonic stimulation, the permeability of membrane and the transport of nutrients were improved, and the utilization rate of substrate and pigment concentration increased 22.7% and 18.4%, respectively. However, excessive ultrasonic irradiation significantly inhibited the cell growth and lipid accumulation of microalgae. This study indicates the feasibility and efficiency of using low-strength ultrasound in promoting biomass and lipid production of microalgae. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Two strains of non-acidophilic microalgae (NAM) were acclimated to pH 3.0. • Flow cytometry analysis indicated their ability to withstand acidic pH. • Both the acclimated strains yielded good amounts of biomass and neutral lipids. • FTIR analysis confirmed accumulation of more triacylglycerols in NAM strains. • First report on biodiesel production in good amounts by NAM strains at pH 3.0. Abstract The overwhelming response towards algal biodiesel production has been well-recognized recently as a sustainable alternative to conventional fuels. Most microalgae cannot grow well at acidic pH. The present study, therefore, investigated whether non-acidophilic microalgae Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3 can be acclimated to extreme-acidic pH for sustainable production of biomass and biodiesel. Growth analysis indicated that both the microalgal strains possessed a passive uptake of CO 2 at pH 3.0 with biomass production of 0.25 g dry wt. L−1 in Desmodemus sp. and 0.45 g dry wt. L−1 in Heterochlorella sp.. Flow-cytometry analysis for reactive oxygen species, membrane permeability and neutral-lipids revealed the capabilities of both strains to adapt to the stress imposed by acidic pH. Lipid production was doubled in both the strains when grown at pH 3.0. In-situ transesterification of biomass resulted in 13–15% FAME yield in the selected microalgae, indicating their great potential in biofuel production. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A heterotrophic-assisted photoautotrophic biofilm growth mode was constructed. • Light penetration capability in the HAPB was 64% stronger than that in the PB. • Nutrients were optimized to improve microalgae biomass and lipid productivity. • Maximum specific growth rate of Chlorella vulgaris increased by 78%. • Lipid content and yield increased by 120% and 147%, up to 47.53% and 41.95 g m−2. Abstract In order to solve the technical bottleneck that the biomass yield and lipid accumulation cannot be increased simultaneously during microalgae growth, a heterotrophic-assisted photoautotrophic biofilm (HAPB) growth mode of Chlorella vulgaris was constructed. The light penetration capability of the microalgae biofilm formed through heterotrophic-assisted photoautotrophic growth was 64% stronger than that formed by photoautotrophic growth. Due to the different demands of autotrophic and heterotrophic growth of microalgae, the nutrient environment and growth conditions were optimized to fully utilize the advantages and potentials of the HAPB culture model. An optimized molar ratio of total inorganic carbon (CO 2) to total organic carbon (glucose) (20:1) and a molar ratio of total carbon to total nitrogen (72:1) were obtained. The maximum specific growth rate of Chlorella vulgaris increased by 78% compared to that before optimization. Meanwhile, the lipid content and yield increased by 120% and 147%, respectively, up to 47.53% and 41.95 g m−2. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Microalgae incubation after PEF-treatment improves water-soluble components release. • Microalgae incubation after PEF-treatment improves lipid extraction yields. • With 20 h of incubation, energy of PEF-treatment can be reduced to 0.25 MJ/kg DW. • Incubation is also efficient at 4 °C but less than at 25 °C. Abstract Pulsed Electric Field (PEF) pre-treatment, applied on fresh microalgae Auxenochlorella protothecoides, induces spontaneous release of a substantial water fraction and enables subsequent lipid extraction using ethanol-hexane blends. In this study, fresh microalgae suspensions were treated with PEF and incubated under inert conditions. Incubation promotes the release of ions and carbohydrates and increases the yields of subsequent lipid extraction thus enabling a considerable reduction of PEF-treatment energy. With a 20 h incubation period at 25 °C, almost total lipid extraction is achieved with a specific PEF-treatment energy of only 0.25 MJ/kg DW. Incubation on ice remains beneficial but less efficient than at 25 °C. Additionally, incubating microalgae cells in suspension at 100 g DW /L or in a dense paste, was almost equally efficient. Correlation between the different results suggests that spontaneous release of ions and carbohydrates facilitates more successful lipid extraction. A direct causality between the two phenomena remains to be demonstrated. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Efficacy of quercetin (Qn) on biomass and lipid was established in C. vulgaris. • Qn potentiates biomass and lipid enhancement despite nitrogen concentration. • Qn improves antioxidant potential of the cells. • Transcriptomic and UPLC-QTOF-MS data uncover the role of Qn in signaling pathway. • Qn hyperaccumulated cellular biomass and lipid by 2.5- and 1.8-fold, respectively. Abstract Provision of chemical modulators has emerged as an effective strategy to govern cell growth and development. Here, the impact of flavonoid quercetin on algal growth, lipid accumulation and transcriptional patterns was investigated in the green microalga Chlorella vulgaris. These results demonstrated that quercetin (15 μg/l) significantly enhanced the cellular biomass and photosynthetic efficiency, with up to 2.5-fold in the biomass in the stationary phase. Lipidomic analyses revealed that lipid content was increased by 1.8-fold. Furthermore, the functional mechanism of quercetin on the molecular level was dissected by transcriptomic analysis. Results revealed that quercetin upregulated the expression pattern of key genes involved in cellular signaling mechanisms such as phosphatidylinositol 4-kinase α, thus consequently enhanced cell growth. Altogether, the data present in this study demonstrate the dramatic role of quercetin on enhancing microalgal biomass and lipid accumulation by unprecedented regulation, of key metabolic nodes, for the first time and provide a novel insight into microalgal metabolism and regulation. [ABSTRACT FROM AUTHOR]

Highlights • We develop a new quadruple substrate kinetic model of microalgal cultivation. • The model accounts for substrate, nutrient, temperature & light intensity dynamics. • We experimentally validate the model through a series of lab-scale experiments. • We use the model to compute optimal conditions to maximise lipid productivity. • We validate experimentally the computed optimal growth parameters. Abstract This paper presents a new quadruple-factor kinetic model of microalgal cultivation considering carbon and nitrogen concentration, light intensity and temperature, developed in conjunction with laboratory-scale experiments using the well-studied chlorophyte microalgal species Chlamydomonas reinhardtii. Multi-parameter quantification was exploited to assess the predictive capabilities of the model. The validated model was utilized in an optimization study to determine the optimal light intensity and temperature for achieving maximum lipid productivity while using optimal acetate and nitrogen concentrations (2.1906 g L−1 acetate and 0.0742 g L−1 nitrogen) computed in a recent publication. It was found that the optimal lipid productivity increased by 50.9% compared to the base case, and by 13.6% compared to the previously computed optimal case. Optimization results were successfully validated experimentally. Such comprehensive modelling approaches can be exploited for robust design, scale-up and optimization of microalgal oil production, reducing operating costs and bringing this important technology closer to industrialization. [ABSTRACT FROM AUTHOR]

Adoption of microalgae-sourced products depends on the economic feasibility. In the case of fatty acids, it is crucial to obtain high lipid yield, especially in the form of storage lipids (TAGs). However, the production of these lipids often comes into competition with the microalgae biomass, resulting in a decrease in growth. A microalgae culture integration project was conducted in an industrial park in Canada in order to cultivate microalgae from park’s wastewaters and then obtain products from the biomass. Different deficiencies and stresses were tested to evaluate what condition allowed the induction of the highest lipids accumulation without compromising the growth of microalgae. The results showed that the medium controlled to pH 7.0 allowed reaching the largest amount of extracted lipids (28 ± 4.3%). Companies involved in this project could be able to make significant savings by the reduced wastewater treatment costs and by not adding expensive nutrients in culture. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chaperone and CRISPRi were first applied in algae under thermophilic condition. • Transcriptional result depicts temperature and CRISPRi effects on algal metabolism. • PGi strain showed 2.56 g/L, 23.5 and 893 mg/L of biomass, lutein and lipid at 35°C. • Thermophilic conditions affect the biomass, lipid, and CO 2 uptake in microalgae. • PGi strain had 1.08 g-CO 2 /g-DCW of CO 2 assimilation ability in mixotrophic culture. Microalgae are widely recognized as a promising bioresource for producing renewable fuels and chemicals. Microalgal biorefinery has tremendous potential for incorporation into circular bioeconomy, including sustainability, cascading use, and waste reduction. In this study, genetic engineering was used to enhance the growth, lipid and lutein productivity of Chlamydomonas reinhardtii including strains of CC400, PY9, pCHS, and PG. Notably, CRISPRi mediated on phosphoenolpyruvate carboxylase (PEPC 1) gene to down-regulate the branch pathway from glycolysis to partitioning more carbon flux to lipid was explored under meso -thermophilic condition. The best chassis PGi, which has overexpressed chaperone GroELS and applied CRISPRi resulting in the highest biomass of 2.56 g/L and also boosted the lipids and lutein with 893 and 23.5 mg/L, respectively at 35°C. Finally, all strains with CRISPRi exhibited higher transcriptional levels of the crucial genes from photosynthesis, starch, lipid and lutein metabolism, thus reaching a CO 2 assimilation of 1.087 g-CO 2 /g-DCW in mixotrophic condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnesium aminoclay (MgA) induces CO 2 absorption and oxidative stress. • The effect of MgA on growth and lipid accumulation is Chlorella strain-dependent. • MgA improved the total lipid content and hexane extractability of Chlorella KR-1. • MgA promoted triacylglycerol biosynthesis but reduced cell wall thickness. Magnesium aminoclay nanoparticles (MgANs) exert opposing effects on photosynthetic microalgae by promoting carbon dioxide (CO 2) uptake and inducing oxidative stress. This study explored the potential application of MgAN in the production of algal lipids under high CO 2 concentrations. The impact of MgAN (0.05–1.0 g/L) on cell growth, lipid accumulation, and solvent extractability varied among three tested oleaginous Chlorella strains (N113, KR-1, and M082). Among them, only KR-1 exhibited significant improvement in both total lipid content (379.4 mg/g cell) and hexane lipid extraction efficiency (54.5%) in the presence of MgAN compared to those of controls (320.3 mg/g cell and 46.1%, respectively). This improvement was attributed to the increased biosynthesis of triacylglycerols and a thinner cell wall based on thin-layer chromatography and electronic microscopy, respectively. These findings suggest that using MgAN with robust algal strains can enhance the efficiency of cost-intensive extraction processes while simultaneously increasing the algal lipid content. [ABSTRACT FROM AUTHOR]

Acetate and ammonium were used as organic carbon and nitrogen sources, respectively, during mixotrophic cultivation of Chlorella pyrenoidosa . Cell growth, content of neutral lipid (NL), productivity of biomass and total lipid, and fatty acid profiles were investigated. Results showed that C. pyrenoidosa could endure high concentrations of NH 4 + -N (100–200 mg/L) and immediately entered logarithmic growth, when the culture media contained 2.0–10.0 g/L NaAc. The 2.0–10.0 g/L NaAc in the media also resulted in the NL content of 1.87–3.05 mg/10 9 cells, much higher than 0.5 mg/10 9 cells of the controls. The maximum productivities of biomass and total lipid were achieved under 50 and 10 mg/L NH 4 + -N respectively when the 2.0 g/L NaAc was dosed. The fatty acids were mainly composed of C16:0, C16:1, C18:0, and C18:1 under the mixotrophic cultivation, with the higher saturation compared to the controls. [ABSTRACT FROM AUTHOR]

In this study, melatonin (MT) promoted lipid accumulation in Monoraphidium sp. QLY-1 under nitrogen deficiency conditions. The lipid accumulation increased 1.22- and 1.36-fold compared with a nitrogen-starved medium and a normal BG-11 medium, respectively. The maximum lipid content was 51.38%. The reactive oxygen species (ROS) level in the presence of melatonin was lower than that in the control group, likely because of the high antioxidant activities. The application of melatonin upregulated the gibberellin acid (GA) production and rbcL and accD expression levels but downregulated the abscisic acid (ABA) content and pepc expression levels. These findings demonstrated that exogenous melatonin could further improve the lipid production in Monoraphidium sp. QLY-1 by regulating antioxidant systems, signalling molecules, and lipid biosynthesis-related gene expression under nitrogen deficiency conditions. [ABSTRACT FROM AUTHOR]

A systematic qualitative and quantitative analysis of fatty acid methyl esters (FAMEs) is crucial for microalgae species selection for biodiesel production. The aim of this study is to identify the best method to assess microalgae FAMEs composition and content. A single-step method, was tested with and without purification steps—that is, separation of lipid classes by thin-layer chromatography (TLC) or solid-phase extraction (SPE). The efficiency of a direct transesterification method was also evaluated. Additionally, the yield of the FAMEs and the profiles of the microalgae samples with different pretreatments (boiled in isopropanol, freezing, oven-dried and freeze-dried) were compared. The application of a purification step after lipid extraction proved to be essential for an accurate FAMEs characterisation. The purification methods, which included TLC and SPE, provided superior results compared to not purifying the samples. Freeze-dried microalgae produced the lowest FAMEs yield. However, FAMEs profiles were generally equivalent among the pretreatments. [ABSTRACT FROM AUTHOR]

In this work, the removal of the Cephalexin by Chlorella sp., nonliving modified by extraction of lipids was evaluated. First, the microalga was grown to completing 20 days and later, the biomass of crop was centrifuged and the extraction of lipids was performed. Two adsorption experiments were performed: (1) with nonliving Chlorella sp. (control), and (2) the obtained biomass after lipid extraction. The high antibiotic removal, 71.19% and 82.77% (control), were obtained at the lowest initial concentration. The contact time between the biosorbent and the antibiotic was 2 h. The adsorption isotherm follows the Freundlich model and the obtained maximum absorption capacity was 63.29 mg of antibiotic/g of biosorbent for lipid-extracted biomass, while the control follows best to the Langmuir model with 129.87 mg/g in maximum absorption capacity. In summary, this biosorbent provides a potential alternative in the removal of Cephalexin. [ABSTRACT FROM AUTHOR]

Samples of nitrogen-starved Parachlorella kessleri containing intact cells (IC), cells ground by bead milling (BM), and cells subjected to high-pressure cell disruption (HPD), together with their supernatants after centrifugation, were compared for granulometry and lipid profiles. The effects of disruption on the lipid profile and organisation were evaluated. The quantity of lipids available for extraction increased with disruption, and up to 81% could be recovered in supernatants after centrifugation, but a marked reorganization occurred. The proportion of amphiphilic free fatty acids and lysophosphatidylcholine increased during disruption due to their release or owing to lipid degradation by enzymes or physical conditions. This effect was more marked in HPD than in BM. Lipids contained in the aqueous phase, after disruption and centrifugation, were enriched in unsaturated fatty acids, BM leading to larger droplets than HPD. The larger liquid lipid droplet would be easier to recover in the following downstream processing. [ABSTRACT FROM AUTHOR]

Considering the variations of optimal light intensity required by microalgae cells along with growth phases, growth-phase light-feeding strategies were proposed and verified in this paper, aiming at boosting microalgae lipid productivity from the perspective of light conditions optimization. Experimental results demonstrate that under an identical time-averaged light intensity, the light-feeding strategies characterized by stepwise incremental light intensities showed a positive effect on biomass and lipid accumulation. The lipid productivity (235.49 mg L −1  d −1 ) attained under light-feeding strategy V (time-averaged light intensity: 225 μmol m −2  s −1 ) was 52.38% higher over that obtained under a constant light intensity of 225 μmol m −2  s −1 . Subsequently, based on light-feeding strategy V, microalgae lipid productivity was further elevated to 312.92 mg L −1  d −1 employing a two-stage based light-feeding strategy V 560 (time-averaged light intensity: 360 μmol m −2  s −1 ), which was 79.63% higher relative to that achieved under a constant light intensity of 360 μmol m −2  s −1 . [ABSTRACT FROM AUTHOR]

Blue and red light-emitting diodes (LEDs) were used to study the effects of wavelength mixing ratios, photoperiod regimes, and green wavelength stress on Nannochloropsis salina , Isochrysis galbana , and Phaeodactylum tricornutum cell biomass and lipid production. The maximum specific growth rates of I . galbana and P . tricornutum were obtained under a 50:50 mixing ratio of blue and red wavelength LEDs; that of N . salina was obtained under red LED. Maximum cell biomass for N . salina and P . tricornutum was 0.75 and 1.07 g dcw/L, respectively, obtained under a 24:0 h light/dark cycle. However, the maximum I . galbana biomass was 0.89 g dcw/L under an 18:6 h light/dark cycle. The maximum lipid contents for N . salina, I . galbana , and P . tricornutum were 49.4, 63.3 and 62.0% (w/w), respectively, after exposure to green LED. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were obtained 1% in P . tricornutum and 2% in I . galbana . [ABSTRACT FROM AUTHOR]

New strains of green microalgae were isolated and screened for growth and the production of lipids from municipal wastewater. It was shown that the strain Micractinium sp. IC-76 has a biomass productivity of 37.18 ± 4.12 mg L −1  d −1 and a lipid content of 36.29 ± 0.11%, with a total content of saturated and monounsaturated fatty acids of 71.9%. The efficiency of nitrogen (N-NH 4 ) and phosphorus (P-PO 4 ) removal was 96.4 ± 0.7 and 77.8 ± 5.6%, respectively. The metabolic differences at the exponential and stationary phases of growth between the closely related strains with different patterns of lipid accumulation were revealed via gas chromatography mass spectrometry metabolic profiling. The strain Micractinium sp. IC-76 in the stationary phase of growth shows a significant difference in carbohydrate metabolism, especially sucrose concentration. High lipid induction during cultivation in wastewater was also driven by changes in the biosynthesis of amino acids, fatty acids and the tricarboxylic acid cycle. [ABSTRACT FROM AUTHOR]

Aiming at alleviating the adverse effect of poor light penetrability on microalgae growth, planar waveguide modules functioned as diluting and redistributing the intense incident light within microalgae culture more homogeneously were introduced into a lab-scale open raceway pond (ORP) for Nannochloropsis oculata cultivation. As compared to the conventional ORP, the illumination surface area to volume ratio and effective illuminated volume percentage in the proposed ORP were respectively improved by 5.53 times and 19.68–172.72%. Consequently, the superior light distribution characteristics in the proposed ORP contributed to 193.33% and 443.71% increase in biomass concentration and lipid yield relative to those obtained in conventional ORP, respectively. Subsequently, the maximum biomass concentration (2.31 g L −1 ) and lipid yield (1258.65 mg L −1 ) was obtained when the interval between adjacent planar waveguide modules was 18 mm. The biodiesel produced in PWM-ORPs showed better properties than conventional ORP due to higher MUFA and C18:1 components proportions. [ABSTRACT FROM AUTHOR]

The effects of an enzymatic treatment with cellulase and mannanase on the properties of marine microalgae Nannochloropsis sp. were investigated. The combined use of these enzymes synergistically promoted the recovery of lipids from the microalgae, increasing the extraction yield from 40.8 to over 73%. Untreated and enzymatically treated microalgae were characterized by chemical analysis and by TGA/DTG, FTIR, XRD and SEM. Significant changes were observed in the chemical composition and thermal behavior of the microalgae. The enzymatic treatment also resulted in an increase of the crystalline-to-amorphous cellulose ratio. SEM images revealed dramatic changes in cell morphology, extensive cell damage and release of intracellular material. Overall, the results obtained indicate that the enzymes used are capable of disrupting the microalgal cell wall and that a combination of common analytical techniques can be used to assess the enzyme-induced damage. [ABSTRACT FROM AUTHOR]

Heterotrophic microalgae, capable of converting organic carbons to biofuel, as well as assimilating nutrients, have a great prospective in wastewater treatment. Meanwhile, the knowledge about heterotrophic microalgae is still far less than the autotrophic conterpart. Hence, in this study, 20 heterotrophic microalgal strains were isolated from a domestic wastewater treatment plant, and identified according to morphology and partial 18S and 23S rRNA gene sequences. Further, their biological traits were assessed in terms of N, P, TOC removal efficiencies, growth parameters, self-settleability and lipids production, expressed through a comprehensive selection index. By such, the optimal strains were chosen and applied back to treat the real wastewater, with or without pretreatment of sterilization. An organic-adaptable strain, i.e., Botryococcus sp. NJD-1, was ultimately recommended to achieve the concurrent biofuel production (up to 61.7% lipid content) and pollutants removal (up to 64.5%, 89.8% and 67.9% for N, P and TOC) in pristine wastewater. [ABSTRACT FROM AUTHOR]

Four solid acid catalysts including graphene oxide (GO), sulfonated graphene oxide (SGO), sulfonated graphene (SG), and sulfonated active carbon (SAC) were used to convert lipids in wet microalgae into biodiesel. The physiochemical properties of the catalysts were characterized with scanning electron microscope, X-ray diffraction, and thermogravimetric analysis. SGO provided the highest conversion efficiency (84.6% of sulfuric acid) of lipids to fatty acid methyl esters (FAME). Whereas SAC converted few lipids into FAME. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and elemental analysis revealed that much higher hydrophilic hydroxyl content in SGO catalyst resulted in a considerable higher conversion efficiency of lipids to FAME than that (48.6%) catalyzed by SG, although SO 3 H groups (0.44 mmol/g) in SGO were less than those (1.69 mmol/g) in SG. Given its higher SO 3 H group content than GO (0.38 mmol/g), SGO had higher conversion efficiency than GO (73.1%), when they had similar hydrophilic hydroxyl contents. [ABSTRACT FROM AUTHOR]

Oleaginous microalga Nannochloropsis sp. was immobilized in alginate gel beads and cultivated under optimal conditions that their growth and lipid production were comparable to those of free cells. The immobilized cells were used in phytoremediation of secondary effluent from palm oil mill and easily recovered by simple sieving method. The immobilized cells contributed to removal of nitrogen and phosphorus >90% and CO 2 mitigation >99%. They also gave the biomass and lipid production of 1.300 ± 0.050 g/L and 0.356 ± 0.097 g/L, respectively. The repeated-batch cultivation improved the biomass and lipid production by 2.66 folds and 1.41 folds, respectively. The scale up in 3 L-fluidized bed photobioreactor gave the maximum biomass of 3.280 ± 0.049 g/L and lipid production of 0.362 ± 0.010 g/L. Fatty acid compositions of Nannochloropsis sp. lipids showed their suitability as biodiesel feedstocks. This system not only contributes as tertiary treatment of industrial effluent and CO 2 mitigation but also low-cost production of renewable energy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Exogenous GAs promoted the metabolism of SMX by C. vulgaris. • When the GAs dose reached 50 mg/L, 91.8 % of SMX was removed. • GAs promoted the production of lipid by microalgae under antibiotic stress. • GAs promoted C. vulgaris to increase antioxidant enzyme activity under SMX stress. • Transcriptome analysis revealed the molecular mechanism of GAs action. In this study, the phytohormone gibberellins (GAs) were used to enhance sulfamethoxazole (SMX) removal and lipid accumulation in the microalgae Chlorella vulgaris. At the concentration of 50 mg/L GAs, the SMX removal achieved by C. vulgaris was 91.8 % while the lipid productivity of microalga was at 11.05 mg/L d-1, which were much higher than that without GAs (3.5 % for SMX removal and 0.52 mg/L d-1 for lipid productivity). Supplementation of GAs enhanced the expression of antioxidase-related genes in C. vulgaris as a direct response towards the toxicity of SMX. In addition, GAs increased lipid production of C. vulgaris by up-regulating the expression of genes related to carbon cycle of microalgal cells. In summary, exogenous GAs promoted the stress tolerance and lipid accumulation of microalgae at the same time, which is conducive to improving the economic benefits of microalgae-based antibiotics removal as well as biofuel production potential. [ABSTRACT FROM AUTHOR]

In this study, the microalga Nannochloropsis gaditana was subjected to acid catalysed steam explosion treatment and the resulting exploded material was subsequently fractionated to separate the different fractions (lipids, sugars and solids). Conventional and vibrational membrane setups were used with several polymeric commercial membranes. Two different routes were followed: 1) filtration + lipid solvent extraction and 2) lipid solvent extraction + filtration. Route 1 revealed to be much better since the used membrane for filtration was able to permeate the sugar aqueous phase and retained the fraction containing lipids; after this, an extraction required a much lower amount of solvent and a better recovering yield. Filtration allowed complete lipid rejection. Dynamic filtration improved permeability compared to the tangential cross-flow filtration. Best membrane performance was achieved using a 5000 Da membrane with the dynamic system, obtaining a permeability of 6 L/h/m 2 /bar. [ABSTRACT FROM AUTHOR]

Microalgae offer excellent opportunities for producing food and fuel commodities, but in colder climates the low growth rates of many varieties may hamper production. In this work, extremophilic Arctic microalgae were tested to establish whether satisfactory growth and lipid production could be obtained at low water temperature. Five species of snow/soil algae originating from Svalbard (78–79°N) were cultivated at 6 °C, reaching high cell densities (maximum dry weight 3.4 g·L −1 ) in batch cultivations, and high productivity (maximum 0.63 g·L −1 ·d −1 ). After 20 days of cultivation total lipids ranged from 28% to 39% of the dry weight, and diverse patterns of neutral lipid (triacylglycerol; TAG) accumulation were observed. The five species largely accumulated unsaturated fatty acyl chains in neutral lipids, especially polyunsaturated C16 series fatty acids, C18:1 n -9 and C18:3 n -3. The results indicate that polar microalgae could provide an opportunity to increase the yields of microalgal biomass and oil products at low temperatures. [ABSTRACT FROM AUTHOR]

Two competitive strategies, fed-batch and sequencing-batch cultivation, were compared in cost-effective biomass production of a high lipid microalgae, Micractinium inermum NLP-F014 using a blended wastewater medium. For fed-batch cultivations, additional nutrient was supplemented at day 2 (FB1) or consecutively added at day 2 and 4 (FB2). Through inoculum size test, 1.0 g-DCW L-1 was selected for the sequencing-batch cultivation (SB) where about 65% of culture was replaced with fresh medium every 2 days. Both fed-batch cultivations showed the maximum biomass productivity of 0.95 g-DCW L-1 d-1, while average biomass productivity in SB was slightly higher as 0.96 ± 0.08 g-DCW L-1 d-1. Furthermore, remained concentrations of organics (426 mg-COD L-1), total nitrogen (15.4 mg-N L-1) and phosphorus (0.6 mg-P L-1) in SB were much lower than those of fed-batch conditions. The results suggested that SB could be a promising strategy to cultivate M. inermum NLP-F014 with the blended wastewater medium. [ABSTRACT FROM AUTHOR]

A simultaneous cell disruption and lipid extraction method is developed for microalgal biodiesel production using a triethylamine/methanol solvent system. Individually, the pure solvents, i.e. triethylamine and methanol, do not exhibit significant enhancement in lipid extraction, but a 3:7 (v/v) triethylamine/methanol mixture exhibits the highest lipid extraction, corresponding to 150% of the conventional chloroform/methanol (2:1, v/v) solvent extraction. This extraction is equivalent to 92.5% of the total lipids, even when extracted from a wet microalgal biomass with a water content of 80%. The cell surfaces of the microalgae are significantly disrupted without using additional cell disruption reagents and without requiring energy-intensive equipment. The lipid mass transfer coefficient is 1.6 times greater than that of the chloroform/methanol solvent system. It is clearly demonstrated that triethylamine and methanol cooperate well for the cell disruption and lipid extraction. [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]

Two-stage cultivation for microalgae biomass is a promising strategy to boost lipid accumulation and productivity. Most of the currently described processes use energy-intensive centrifugation for cell separation after the first cultivation stage. This laboratory study evaluated alkaline flocculation as low-cost alternative separation method to harvest Nannochloropsis oculata prior to cultivation in the second nutrient-depleted cultivation stage. Biomass concentration over time and the maximum quantum yield of photosystem II expressed as Fv:Fm ratio showed identical patterns for both harvesting methods in both stages. The composition of total lipids, carbohydrates, and protein was similar for biomass harvested via alkaline flocculation or centrifugation. Likewise, both harvest methods yielded the same increase in total lipid content, to 40% within the first 2 days of the nutrient-depleted stage, with an enrichment in C16 fatty acid methyl esters. Centrifugation can therefore be replaced with alkaline flocculation to harvest Nannochloropsis oculata after the first cultivation stage. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effectiveness of cultivating Parachlorella kessleri and Acutodesmus obliquus , in anaerobic digestion effluent (ADE) derived from the co-digestion of end-of-life dairy products with mixtures of agro-industrial wastes. To this end, their performance under sterile and non-sterile conditions and different ADE loadings was evaluated, in terms of biomass and lipid production, nutrient removal efficiency and vitality of the photosynthetic apparatus. 10% (v/v) ADE loading inhibited growth over 9–12 days of cultivation, however biomass yields of 1.1 and 1 g L −1 , 22.7% and 19.5% (w/w) fatty acids concentration, as well as NH 3 -N assimilation of 49.7 mg L −1 and 32.3 mg L −1 and TP removal of 84.2% and 84% were recorded for P. kessleri and A. obliquus , respectively. Among all the ADE-based treatments tested, P. kessleri outperformed A. obliquus , with no differences observed between sterilized and non-sterilized ADE. [ABSTRACT FROM AUTHOR]

Cultivation of microalgae Chlorella sp. with livestock waste compost as an alternative nutrient source was investigated in this present study. Five culture media with different nutrient concentrations were prepared. The characteristics of algal growth and lipid production were examined. The results showed that the specific growth rate together with biomass and lipid productivities was different among all the cultures. As the initial nutrient concentration decreased, the lipid content of Chlorella sp. increased. The variations in lipid productivity of Chlorella sp. among all the cultures were mainly due to the deviations in biomass productivity. The livestock waste compost medium with 2000 mg L −1 COD provided an optimal nutrient concentration for Chlorella sp. cultivation, where the highest productivities of biomass (288.84 mg L −1 day −1 ) and lipid (104.89 mg L −1 day −1 ) were presented. [ABSTRACT FROM AUTHOR]

[Display omitted] • 91.51 % of DFS was removed by C. sorokiniana within 9 days. • DFS promoted microalgal growth by 12.83% (DCW). • DFS enhanced chlorophylls (28.6%), carotenoids (27.6%), and lipids (30.2%). • Increased level of SFA and MUFA upon DFS removal. • Metabolomics & enzyme assays elucidated the mechanism of DFS removal. The aim of this work was to assess the efficiency of freshwater green microalga, Chlorella sorokiniana for diclofenac sodium (DFS) removal, and metabolic response of alga to comprehend the metabolic pathways involved/affected during DFS decontamination. Results showed 91.51 % removal of DFS could be achieved within 9 days of algal treatment along with recovery of enhanced value-added bioresources i.e. chlorophyll, carotenoids, and lipids from the spent biomass. DFS also had an effect on enzyme activity including superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation (MDA). Furthermore, metabolomics profiling provided an in-depth insight into changes in the metabolic response of C. sorokiniana wherein DFS induced 32 metabolites in microalgae compared to unexposed-control. This study offers microalgae as a green option for DFS removal, and the metabolomics study complemented with DFS could be an approach to understand the stress-induced strategies of C. sorokiniana for concomitant value-added products recovery in presence of DFS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microalgal represents 3G feedstock for renewable fuels, chemical and energy production. • Green pretreatment/ extraction processes for sugars, lipids and proteins have been outlined. • Aqueous biphasic systems with suitable cations/ anions may promote high extraction yield. • Integrated microalgal biorefinery development will enhance bioresource recovery. • Biodegradability and recyclability are core areas that need to explore for scale-up activity. Microalgae enable fixation of CO 2 into carbohydrates, lipids, and proteins through inter and intracellularly biochemical pathways. These cellular components can be extracted and transformed into renewable energy, chemicals, and materials through biochemical and thermochemical transformation processes. However, recalcitrant cell wall and lack of environmentally benign efficient pretreatment processes are key obstacles in the commercialization of microalgal biorefineries. Thus, current article describes the microalgal chemical structure, type, and structural rigidity and summarizes the traditional pretreatment methods to extract cell wall constituents. Green solvents such as ionic liquid (ILs), deep eutectic solvents (DES), and natural deep eutectic solvents (NDESs) have shown interesting solvent characteristics to pretreat biomass with selective biocomponent extraction from microalgae. Further research is needed in task-specific IL/DES design, cation–anion organization, structural activity understanding of ILs-biocomponents, environmental toxicity, biodegradability, and recyclability for deployment of carbon–neutral technologies. Additionally, coupling the microalgal industry with biorefineries may facilitate waste management, sustainability, and gross revenue. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phytohormones increased the growth rate of microalgae under salt stress. • Phytohormones further increased the microalgal lipid content based on salt stress. • 2 g/L salt and ABA increased lipid productivity to 3.7 times that of control. • DEGs of microalgae were mainly up-regulated under phytohormones except BL. • The regulation of different phytohormones is related to homologous recombination. In this study, a novel method of coupling phytohormones with saline wastewater was proposed to drive efficient microalgal lipid production. All the six phytohormones effectively promoted microalgae growth in saline wastewater, and further increased the microalgal lipid content based on salt stress, so as to achieve a large increase in microalgal lipid productivity. Among the phytohormones used, abscisic acid had the most significant promoting effect. Under the synergistic effect of 20 g/L salt and 20 mg/L abscisic acid, the microalgal lipid productivity reached 3.7 times that of the control. Transcriptome analysis showed that differentially expressed genes (DEGs) of microalgae in saline wastewater were mainly up-regulated under the effects of phytohormones except brassinolide. Common DEGs analysis showed that phytohormones all regulated the expression of genes related to DNA repair and substance synthesis. In conclusion, synergistic effect of salt stress and phytohormones can greatly improve the microalgal lipid production efficiency. [ABSTRACT FROM AUTHOR]

The aim of this work is to compare the life cycle assessments of low-N and normal culture conditions for a balance between the lipid content and specific productivity. In order to achieve the potential contribution of lipid content to the life cycle assessment, this study established relationships between lipid content (nitrogen effect) and specific productivity based on three microalgae strains including Chlorella , Isochrysis and Nannochloropsis . For microalgae-based aviation fuel, the effects of the lipid content on fossil fuel consumption and greenhouse gas (GHG) emissions are similar. The fossil fuel consumption (0.32–0.68 MJ·MJ −1 MBAF) and GHG emissions (17.23–51.04 g CO 2 e·MJ −1 MBAF) increase (59.70–192.22%) with the increased lipid content. The total energy input decreases (2.13–3.08 MJ·MJ −1 MBAF, 14.91–27.95%) with the increased lipid content. The LCA indicators increased (0–47.10%) with the decreased nitrogen recovery efficiency (75–50%). [ABSTRACT FROM AUTHOR]

The present study aimed to develop thermo-tolerant mutants of Chlorella pyrenoidosa NCIM 2738 for high lipids production. For this, ethyl methane sulfonate was used, which generated two effective thermo-tolerant mutants, M18 and M24 of Chlorella pyrenoidosa NCIM 2738, capable of surviving at temperature up to 47 °C and showing improved lipid and biomass yields. They showed 59.62% and 50.75% increase, respectively in lipid content compared to wild type at 30 °C, which could not grow at temperature above 35 °C. The novelty of this study lied in incorporation of PAM Flurometry with mutagenesis to generate thermo-tolerant mutants of C. pyrenoidosa and investigating the reasons for increased yields of mutants at cellular and photosynthetic levels with the aim to use them for commercial biodiesel production. [ABSTRACT FROM AUTHOR]

In order to produce biodiesel from lipids in wet microalgae with graphene oxide (GO) as solid acid catalyst, the effects on lipids conversion efficiencies of catalyst dosage, transesterification temperature, reaction time, methanol dosage and chloroform dosage were investigated. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and elemental analysis revealed that GO contained 0.997 mmol SO 3 H groups per gram and high amounts of OH groups. Scanning electron microscopy showed that wet microalgae cells were adsorbed on hydrophilic GO surfaces covered with many OH groups. Lipids extracted by chloroform from microalgal cells were transformed into fatty acids methyl esters (FAMEs) through transesterification catalyzed by the acid centers (SO 3 H groups) in GO catalysts. The lipids conversion efficiency into FAMEs was 95.1% in microwave-assisted transesterification reactions of 5 wt.% GO catalyst at 90 °C for 40 min. [ABSTRACT FROM AUTHOR]

This study investigates the year-round production potential and quality of biodiesel from wastewater treatment high rate algal pond (WWT HRAP) biomass and how it is affected by CO 2 addition to the culture. The mean monthly pond biomass and lipid productivities varied between 2.0 ± 0.3 and 11.1 ± 2.5 g VSS/m 2 /d, and between 0.5 ± 0.1 and 2.6 ± 1.1 g/m 2 /d, respectively. The biomass fatty acid methyl esters were highly complex which led to produce low-quality biodiesel so that it cannot be used directly as a transportation fuel. Overall, 0.9 ± 0.1 g/m 2 /d (3.2 ± 0.5 ton/ha/year) low-quality biodiesel could be produced from WWT HRAP biomass which could be further increased to 1.1 ± 0.1 g/m 2 /d (4.0 ton/ha/year) by lowering culture pH to 6–7 during warm summer months. CO 2 addition, had little effect on both the biomass lipid content and profile and consequently did not change the quality of biodiesel. [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 goal of the present study was to investigate the pH range that can support the growth of C. vulgaris , and, more specifically, to identify the optimal pH for the microalga’s growth, under heterotrophic conditions. Furthermore, the effect of pH on the accumulation of intracellular lipids was studied. A wide range of pH values was tested using the respective buffer solutions. The optimal pH for biomass growth and lipid accumulation under sulfur limitation was found to be 7.5, resulting in maximum specific growth rate of 0.541 days −1 and maximum total lipid content of 53.43% g g DW −1 . The fatty acid composition of C. vulgaris was found to be unrelated to pH, as the lipid content did not present significant variations in the pH values tested. The fatty acid profile was mainly composed of monounsaturated fatty acids (MUFAs) with the dominant one being oleic acid (C18:1). [ABSTRACT FROM AUTHOR]

In the present work we wanted to know what happens during time to biomass and lipid productivities of Chlorococcum littorale repeatedly subjected to N-starvation. Experiments were done using repeated cycles of batch-wise N run-out (after 2 days N = 0). Two different cycles were used: repeated short-starvation (6 days of N = 0) over a total period of 72 days and repeated long-starvation (13 days of N = 0) over a total period of 75 days. Batches (using fresh inocula) were done separately as control. Shorter and longer periods of starvation showed no differences in biomass productivities and PSII quantum yield evolution. The repeated short-starvation-batches showed the same lipid productivities as the control short-starvation batches. Most importantly, the biomass lipid content was the same between control and repeated-batches. Altogether, the results point to C. littorale as a resilient and stable strain, with potential to be used under semi continuous cultivation. [ABSTRACT FROM AUTHOR]

Oleaginous microalgae Nannochloropsis sp. was selected as potential strain for CO 2 mitigation into lipids and pigments. The synergistic effects of light intensity and photoperiod were evaluated to provide the adequate light energy for this strain. The saturation light intensity was 60 μmol·photon·m −2 s −1 . With full illumination, the biomass obtained was 0.850 ± 0.16 g·L −1 with a lipid content of 44.7 ± 1.2%. The pigments content increased with increasing light energy supply. Three main operating factors including initial cell concentration, CO 2 content and gas flow rate were optimized through Response Surface Methodology. The feedings with low CO 2 content at high gas flow rate gave the maximum biomass but with low lipid content. After optimization, the biomass and lipid production were increased up to 1.30 ± 0.103 g·L −1 and 0.515 ± 0.010 g·L −1 , respectively. The CO 2 fixation rate was as high as 0.729 ± 0.04 g·L −1 d −1 . The fatty acids of Nannochloropsis sp. lipids were mainly C16-C18 indicating its potential use as biodiesel feedstocks. [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]

Filamentous microalgae Tribonema is promising for biodiesel production in terms of high lipid content, easy harvesting and good contamination tolerance. As high lipid productivity is a key basis, several methods including different culture medium, phosphorus, iron and CO 2 inductions were tested to enhance lipid productivity in Tribonema minus . T. minus subjected to BG11-freshwater medium achieved a favorable lipid productivity of 216.18 mg L −1 d −1 , much higher than those in other culture medium (BG11-S, Kuhl, f/2, f, 2f, BBM, ASW and ES). Secondly, the optimal phosphorus, iron and CO 2 concentrations for high lipid productivity of T. minus were obtained, respectively. Finally, the cells of T. minus grown in optimized BG11 medium containing 80 mg L −1 KH 2 PO 4 and 6 mg L −1 FeC 6 H 5 O 7 ·NH 4 OH with 2% CO 2 achieved a lipid productivity of 384.67 mg L −1 d −1 , representing a 1.56-fold increase from the control. Therefore, the strategy to enhance lipid productivity of T. minus was successfully proposed. [ABSTRACT FROM AUTHOR]