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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]

During the study of Trentepohlia arborum it became clear that its cells are rich in lipids and carotenoids. Thus, lipid content, composition and fatty acids profiles in individual lipid classes, as well as pigment profiles, responding to different culture conditions, were further investigated. The results showed that the predominant carotenoids and lipid fraction in total lipid in this study was β -carotene and TAG, respectively. The lipid content increased significantly under high light while nitrogen-replete conditions induced the highest carotenoids content. However, only with a double stress of high light and nitrogen-deficiency it was possible to maximize the productivities of both carotenoids and lipids. Carotenoids (mainly β -carotene) accounted for ca . 5% of the microalgal lipid under the double stress. Data herein show the potential of T. arborum for the production of both lipids and carotenoids, and hence provide an appropriate way to produce different products from T. arborum . [ABSTRACT FROM AUTHOR]

This study evaluated the suitability of pinewood pyrolysates as a carbon source for lipid production and cultivation of the oleaginous yeast Rhodosporidium diobovatum and the microalgae Chlorella vulgaris . Thermal decomposition of pinewood and fractional condensation were used to obtain an oil rich in levoglucosan which was upgraded to glucose by acid hydrolysis. Blending of pyrolytic sugars with pure glucose in both nitrogen rich and nitrogen limited conditions was studied for R. diobovatum , and under nitrogen limited conditions for C. vulgaris . Glucose consumption rate decreased with increasing proportions of pyrolytic sugars increasing cultivation time. While R. diobovatum was capable of growth in 100% (v/v) pyrolytic sugars, C. vulgaris growth declined rapidly in blends greater than 20% (v/v) until no growth was detected in blends >40%. Finally, the effects of pyrolysis sugars on lipid composition was evaluated and biodiesel fuel properties were estimated based on the lipid profiles. [ABSTRACT FROM AUTHOR]

Mixotrophic growth of microalgae to boost lipid production is currently under active investigation. Such a process could be of practical importance if a cheap source of organic carbon, such as waste glycerol from biodiesel production, could be used. Several previous studies have already demonstrated that this carbon source can be used by different indigenous strains of microalgae. In this study it is shown that different nitrogen limitation strategies can be applied to further increase lipid production during growth with glycerol. In one strategy, cultures were grown in nitrogen replete medium and then resuspended in nitrogen free medium. In a second strategy, cultures were grown with different initial concentrations of nitrate. Lipid production by the two microalgal strains used, Chlorella sorokiniana (PCH02) and Chlorella vulgaris (PCH05), was shown to be boosted by strategies of nitrogen limitation, but they responded differently to how nitrogen limitation was imposed. [ABSTRACT FROM AUTHOR]

Municipal wastewater sludge is a promising lipid feedstock for biodiesel production, but the need to eliminate the high water content before lipid extraction is the main limitation for scaling up. This study evaluates the economic feasibility of biodiesel production directly from liquid primary sludge based on experimental data at laboratory scale. Computational tools were used for the modelling of the process scale-up and the different configurations of lipid extraction to optimise this step, as it is the most expensive. The operational variables with a major influence in the cost were the extraction time and the amount of solvent. The optimised extraction process had a break-even price of biodiesel of 1232 $/t, being economically competitive with the current cost of fossil diesel. The proposed biodiesel production process from waste sludge eliminates the expensive step of sludge drying, lowering the biodiesel price. [ABSTRACT FROM AUTHOR]

High moisture content in wet algal biomass hinders effective performance of current lipid extraction methods. An improved aqueous extraction method combing thermal and enzymatic lysis was proposed and performed in algal slurry of Nannochloropsis oceanica (96.0% moisture) in this study. In general, cell-wall of N. oceanica was disrupted via thermal lysis and enzymatic lysis and lipid extraction was performed using aqueous surfactant solution. At the optimal conditions, high extraction efficiencies for both lipid (88.3%) and protein (62.4%) were obtained, which were significantly higher than those of traditional hexane extraction and other methods for wet algal biomass. Furthermore, an excessive extraction of polar lipid was found for wet biomass compared with dry biomass. The advantage of this method is to efficiently extract lipids from high moisture content algal biomass and avoid using organic solvent, indicating immense potential for commercial microalgae-based biofuel production. [ABSTRACT FROM AUTHOR]

A mixed culture of microalgae, containing two Scenedesmus species, was analysed to determine its potential in coupling of pulp and paper mill effluent treatment and microalgal cultivation. Laboratory studies suggested that 60% concentration of wastewater was optimum for microalgal cultivation. A maximum of 82% and 75% removal of BOD and COD respectively was achieved with microalgal cultivation in outdoor open pond. By the end of the cultivation period, 65% removal of NO 3 -N and 71.29% removal of PO 4 -P was observed. The fatty acid composition of mixed microalgal culture cultivated with effluent showed the palmitic acid, oleic acid, linoleic acid and α-linolenic acid as major fatty acids. The results obtained suggest that pulp and paper mill effluent could be used effectively for cultivation of microalgae to minimise the freshwater and nutrient requirements. [ABSTRACT FROM AUTHOR]

To understand in which way the structural differences of three marine microalgae ( Nannochloropsis gaditana , Rhodomonas marina and Isochrysis sp.) affect their carbon partitioning, growth and applicability; a stoichiometric imbalance was imposed by steady carbon and other nutrients variation. Towards high nutrients concentrations/low carbon availability a decrease of 12–51% in C/N microalgae ratio was observed and maximum cell densities were achieved. Moreover, linear correlation between the nutrient input and microalgae protein content were observed. The macromolecular ratios pointed that carbohydrate was the main contributor for the C/N decrement. Although lipid content in R. marina remained constant throughout the experiment, a rise of 37–107% in N. gaditana and Isochrysis sp. was verified. Lipid fractions revealed high percentages of glycolipids in all microalgae (57–73% of total lipids). The present study shows an easy way to understand and modulate microalgae carbon partitioning relying on the field of application. [ABSTRACT FROM AUTHOR]

Biomass productivity and growth kinetics for microalgae grown on sodium bicarbonate and diammonium phosphate were investigated. Different carbon and nitrogen ratios have shown different growth rates and biomass productivity and C:N ratio 50:10 as mg L −1 has shown the best production than all. For effective lipids extraction from biomass thermolysis and sonolysis were carried out from wet biomass. Sonolysis at 2.3 W intensity for 5 min has released 8.58 mg at neutral pH. More quantity of lipids was extracted when extraction was made at pH 4 and 10 which resulted 9 mg and 9.28 mg lipids respectively. Thermal treatment at 100 °C for 10 min has released 12.82 mg lipid at neutral pH. In the same thermolysis at pH 4 and 10 more quantity of lipids was extracted which were 15.16 mg and 14.81 mg respectively. Finally transesterified lipids were analyzed through GC–MS for FAME composition analysis. [ABSTRACT FROM AUTHOR]

Paper mill sludge (PMS) was assessed as cheap renewable lignocellulosic biomass for lipid production by the oleaginous yeast Cryptococcus vishniaccii (MTCC 232). The sonicated paper mill sludge extract (PMSE) exhibited enhanced lipid yield and lipid content 7.8 ± 0.57 g/l, 53.40% in comparison to 5.5 ± 0.8 g/l, 40.44% glucose synthetic medium, respectively. The accumulated triglycerides (TAG) inside the lipid droplets (LDs) were converted to biodiesel by transesterification and thoroughly characterized using GC–MS technique. The fatty acid methyl ester (FAME) profile obtained reveals elevated content of oleic acid followed by palmitic acid, linoleic acid and stearic acid with improved oxidative stability related to biodiesel quality. [ABSTRACT FROM AUTHOR]

Cell disruption by bead milling of Neochloris oleoabundans grown under nitrogen repleted (NR) and nitrogen depleted (ND) conditions was evaluated based on the release of biochemicals and biomass to the supernatant. Additionally, energy consumption for cell disruption was calculated per kg of released component. Bead milling of NR cells resulted on average in 34% (w/w) release of biochemicals into the supernatant, with a similar composition as the untreated microalgal biomass. With ND cells, the release was higher and more selective, i.e. 57%, 59%, 68% and 56% (w/w) of respectively biomass, proteins, carbohydrates and lipids whereof 92%, 57% and 46% (w/w) respectively of phospho-, glyco- and neutral lipids. [ABSTRACT FROM AUTHOR]

This study fundamentally investigated the pseudo-catalytic transesterification of dried Nannochloropsis oceanica into fatty acid methyl esters (FAMEs) without oil extraction, which was achieved in less than 5 min via a thermo-chemical pathway. This study presented that the pseudo-catalytic transesterification reaction was achieved in the presence of silica and that its main driving force was identified as temperature: pores in silica provided the numerous reaction space like a micro-reactor, where the heterogeneous reaction was developed. The introduced FAME derivatization showed an extraordinarily high tolerance of impurities ( i.e ., pyrolytic products and various extractives). This study also explored the thermal cracking of FAMEs derived from N. oceanica : the thermal cracking of saturated FAMEs was invulnerable at temperatures lower than 400 °C. Lastly, this study reported that N. oceanica contained 14.4 wt.% of dried N. oceanica and that the introduced methylation technique could be applicable to many research fields sharing the transesterification platform. [ABSTRACT FROM AUTHOR]

Conditions of light-emitting diode (LED) wavelength, light intensity, nitrate concentration, and time of exposure to green LED light stress in a two-phase culture were optimized for lipid production with three species of microalgae. Among the three microalgae, Nannochloropsis oculata showed the highest specific growth rate ( μ max ) of 0.037 h −1 and the lowest saturation constant ( K s ) of 1.32 mg/L. The highest lipid contents of the three microalgae in the second phase under green LED light stress were 52.0% (w/w) for Nannochloropsis salina at 2 days, 53.0% (w/w) for Nannochloropsis oceanica at 2 days, and 56.0% for N. oculata at 2 days. Fatty acid analysis of the microalgae showed that 85–87% (w/w) of total fatty acids from N. salina , N. oceanica , and N. oculata consisted of palmitic acid (C16:0) and oleic acid (C18:1). [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 statistical mixture design approach was used to investigate the effects of cell wall degrading enzymes on the recovery of lipids from Nannochloropsis sp. A preliminary screening of potentially suitable enzyme preparations, including lysozyme, cellulase and different types of hemicellulases, was carried out. The most effective preparations were then taken as basic components for the formulation of enzyme mixtures. Optimized ternary mixtures consisting of cellulase and two hemicellulases were obtained which allowed the recovery of up to 37.2 g of lipids per 100 g of dry biomass. SEM and TEM images of the enzymatically treated microalga revealed extensive cell damage, with degradation of the cell wall and release of intracellular material. Overall, the results obtained demonstrate that the mixture design method can be used to prepare cell wall degrading enzyme cocktails that can significantly improve the recovery of lipids or other valuable components from microalgae. [ABSTRACT FROM AUTHOR]

Taxonomy and phylogeny of twenty two microalgal isolates were examined using both universal and newly designed molecular primers. Among the isolates, Scenedesmus bijugus , Coelastrella sp., Auxenochlorella protothecoides , and Chlorella sp. were particularly promising in terms of producing lipids as measured by fatty acid methyl esters (FAME) analysis and significant concentration of carotenoids. A comparative experiment showed that S. bijugus and Chlorella sp. were the most promising candidates (L − 1 d − 1 , with biomass) 174.77 ± 6.75, 169.81 ± 5.22 mg, lipids 40.14 ± 3.31, 39.72 ± 3.89 mg, lutein 0.47, 0.36 mg, and astaxanthin 0.27, 0.18 mg respectively. The fatty acids produced by these microalgal isolates were mainly palmitic, stearic, oleic, linoleic, and linolenic acid. The freshwater microalgal isolate S. bijugus be the most suitable isolate for producing biodiesel and carotenoids, due to high productivity of biomass, lipids, metabolites, and its suitable fatty acid profile. [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]

A novel mathematical model for the quantitative assessment of the effect of dissolved nitrogen on the autotrophic batch-growth and lipid accumulation of Chlorella sorokiniana , is proposed in this work. Model results have been validated through comparison with suitable experimental data performed in lab photobioreactors. Further experiments have been then performed using the BIOCOIL photobioreactor operated in fed-batch mode. The experimental results, which show that a maximum growth rate of 0.52 day −1 and a lipid content equal to 25 %wt can be achieved with the BIOICOIL, have been successfully predicted through the proposed model. Therefore, the model might represent a first step toward the development of a tool for the scale-up and optimization of the operating conditions of BIOCOIL photobioreactors. Finally, the fatty acid methyl esters obtained by trans-esterification of lipids extracted from C. sorokiniana , have been analyzed in view of the assessment of their usability for producing biodiesel. [ABSTRACT FROM AUTHOR]

Pure volatile fatty acid (VFA) solution derived from waste activated sludge (WAS) was used to produce microbial lipids as culture medium in this study, which aimed to realize the resource recovery of WAS and provide low-cost feedstock for biodiesel production simultaneously. Cryptococcus curvatus was selected among three oleaginous yeast to produce lipids with VFAs derived from WAS. In batch cultivation, lipid contents increased from 10.2% to 16.8% when carbon to nitrogen ratio increased from about 3.5 to 165 after removal of ammonia nitrogen by struvite precipitation. The lipid content further increased to 39.6% and the biomass increased from 1.56 g/L to 4.53 g/L after cultivation for five cycles using sequencing batch culture (SBC) strategy. The lipids produced from WAS-derived VFA solution contained nearly 50% of monounsaturated fatty acids, including palmitic acid, heptadecanoic acid, ginkgolic acid, stearic acid, oleic acid, and linoleic acid, which showed the adequacy of biodiesel production. [ABSTRACT FROM AUTHOR]

In the current study it has been hypothesized that, when organic loading of an anaerobic reactor is increased, the additional cell biomass biosynthesis would capture more ammonia nitrogen and thereby reduce the ammonia toxicity. Therefore, the alleviation of the toxicity of high ammonia levels using lipids (glycerol trioleate-GTO) or carbohydrates (glucose-GLU) as co-substrates in manure-based thermophilic continuous stirred-tank reactors (R GTO and R GLU , respectively) was tested. At 5 g NH 4 + -N L −1 , relative methane production of R GTO and R GLU , was 10.5% and 41% compared to the expected uninhibited production, respectively. At the same time control reactor (R CTL ), only fed with manure, reached 32.7% compared to the uninhibited basis production. Therefore, it seems that using lipids to counteract the ammonia effect in CSTR reactors creates an “ammonia–LCFA (long chain fatty acids) synergetic co-inhibition” effect. Moreover, co-digestion with glucose in R GLU was more robust to ammonia toxicity compared to R CTL . [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]

In this study, crude glycerol from various industries was used to produce lipids via wild type Yarrowia lipolytica A101. We tested samples without any prior purification from five different waste products; each contained various concentrations of glycerol (42–87%) as the sole carbon source. The best results for lipid production were obtained for medium containing glycerol from fat saponification. This reached 1.69 g L −1 (25% of total cell dry weight) with a biomass yield of 0.17 g g −1 in the flasks experiment. The batch cultivation in a bioreactor resulted in enhanced lipid production—it achieved 4.72 g L −1 with a biomass yield 0.21 g g −1 . Moreover, the properly selected batch of crude glycerol provides a defined fatty acid composition. In summary, this paper shows that crude glycerol from soap production could be efficiently converted to single cell oil without any prior purification. [ABSTRACT FROM AUTHOR]

To improve nutrients removal from wastewater and enhance lipid production, cultivation of Chlorella vulgaris in wastewater with waste glycerol generated from biodiesel production using scum derived oil as feedstock was studied. The results showed that nutrients removal was improved and lipid production of C. vulgaris was enhanced with the addition of waste glycerol into wastewater to balance its C/N ratio. The optimal concentration of the pretreated glycerol for C. vulgaris was 10 g L −1 with biomass concentration of 2.92 g L −1 , lipid productivity of 163 mg L −1 d −1 , and the removal of 100% ammonia and 95% of total nitrogen. Alkaline conditions prompted cell growth and lipid accumulation of C. vulgaris while stimulating nutrients removal. The application of the integration process can lower both wastewater treatment and biofuel feedstock costs. [ABSTRACT FROM AUTHOR]

Biofuel production from microalgae requires energy efficient processes for extracting and converting triacylglyceride lipids to fuel, compatible with coproduction of protein feeds and nutraceuticals. Wet solvent extraction involves mechanical cell rupture, lipid extraction via solvent contacting, physical phase separation, thermal solvent recovery, and transesterification. A detailed analysis of the effect of key process parameters on the parasitic energy demand of this process was performed. On a well-to-pump basis, between 16% and 320% of the resultant biodiesel energy was consumed depending solely on the process parameters. Highly positive energy balances can be achieved, but only if a correctly designed process is used. This requires processing concentrated biomass ( ca 25% w/w) with a high triacylglyceride content ( ca 30% w/w), and an efficient extraction process employing a non-polar solvent, low solvent-to-paste ratio, and efficient energy recovery. These requirements preclude many laboratory scale processes and polar co-solvents as viable options for large-scale biofuel production. [ABSTRACT FROM AUTHOR]

Non-polar and polar solvents as well as their mixtures were tested for the extraction of microalgae lipids and thus, to evaluate their effect on total and esterifiable lipids extraction yields with potential to be converted to biodiesel. The obtained results show an increase in lipids and esterifiable lipids extraction yields when non-polar and polar solvent mixtures were used. The higher esterifiable lipids extraction yield was 19.2% wt (based on dry biomass) using a chloroform–methanol mixture (75% v/v of methanol), corresponding to a 98.9% wt esterifiable lipids extraction. In addition, esterifiable lipids extraction yield of 18.9% wt (based on dry biomass) was obtained when a petroleum ether–methanol mixture (75% v/v of methanol) was used, corresponding to a 96.9% wt esterifiable lipids extraction. [ABSTRACT FROM AUTHOR]

Kelp waste extracts (KWE) contained massive soluble sugars, amino acids and various mineral elements. To probe the effects of KWE on microalgal physiological and biochemical responses, the cultures were carried out under the different dilutions. The results showed that 8.0% KWE increased the biomass productivities and total lipid contents of Chlorella strains dramatically, which were 1.83–31.86 times and 20.78–25.91% higher than that of the control. Phaeodactylum tricornutum and Spirulina maxima presented a better growth performance in 1.0% and 4.0% treatment respectively, while their lipid accumulation were not enhanced. In Chlorella -Arc, Chlorella sorokiniana and P. tricornutum , the contents of saturated and monounsaturated fatty acids could be increased, and polyunsaturated fatty acids could be decreased under the conditions of high concentration of KWE (6.0–8.0%). Briefly, KWE facilitated to enhance the biomass productivity and lipid content of Chlorella strains, also improved the fatty acid compositions for biodiesel production. [ABSTRACT FROM AUTHOR]

Crude polysaccharides and proteins extracted from algae were chosen as model materials to investigate the hydrothermal liquefaction (HTL) characteristics and pathways of low-lipid algae. Liquefaction behavior of the two individuals and their binary mixtures with different mass ratios were evaluated under different temperatures. Formation pathways of bio-oil from crude polysaccharides/proteins were proposed. Results showed that polysaccharides had a small contribution to bio-oil (<5%) and approximately 60% distributed in aqueous phase, while proteins played a crucial role on bio-oil formation (maximum 16.29%). Bio-oil from polysaccharides mainly contained cyclic ketones and phenols and from proteins composed of pyrazines, pyrroles and amines. Interaction between polysaccharides and proteins forming polycyclic nitrogenous compounds had a negative effect on bio-oil yield at 220 and 260 °C. However, their further decomposition caused increase of bio-oil yield at 300 °C. Mixture liquefaction obtained the highest higher heating value (HHV) of bio-oil and energy recovery than polysaccharides/proteins liquefaction at 300 °C. [ABSTRACT FROM AUTHOR]

Chlorella protothecoides is a valuable source of lipids that may be used for biodiesel production. The present work shows analysis of the potential of photoheterotrophic cultivation of C. protothecoides under various light intensities aiming to identify the conditions with maximal biomass and lipid content. An increase in light intensity was associated with an increased specific growth rate and a shortened doubling time. Also, the relative total lipid content increased from 24.8% to 37.5% with increase of light intensity. The composition of fatty acid methyl esters was affected by light intensity with the C16–18 fatty acids increased from 76.97% to 90.24% of total fatty acids. However, the content of linolenic acids decreased with the increase of the culture irradiance. These studies indicate that cultures irradiated with high light intensities achieve the minimal specifications for biodiesel quality on linolenic acids and thus are suitable for biodiesel production. [ABSTRACT FROM AUTHOR]

This study presents gravimetric enrichment of mixed culture to screen starch and lipid producing species separately in a sequencing batch reactor. In the enriched starch-producing mixed culture photobioreactor, the starch content at the end of steady state batch became 3.42 times the beginning of depletion. Whereas in the enriched lipid-producing photobioreactor, the lipid content at the end of steady state batch became 3 times the beginning of famine phase. The obtained results revealed that the gravimetric enrichment is a suitable screening method for specific production of storage compounds in none-sterile large-scaled condition. [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]

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 pore structures and surface morphological characteristics of Nannochloropsis sp. cells with arsenic adsorption were initially investigated by N 2 -adsorption analysis and scanning electronic microscopy. Functional groups of cells were analysed by Fourier-transform infrared spectrometry and X-ray photoelectron spectroscopy. Total surface area of microalgal cells increased from 0.54 m 2 /g to 1.80 m 2 /g upon arsenic adsorption. The external cell surface area increased. More wrinkles and measles-like granules formed on the surfaces as a result of arsenic toxicity. Arsenic ions blocked cell pores and decreased the average pore diameter and total pore volume. Ether cross-linked structures in the algaenan layer of cell walls were disrupted as the percentage of C–O functional groups decreased. These functional groups underwent complexation reactions with arsenic ions. Accumulation of polyunsaturated fatty acids decreased because of oxidative stresses induced by arsenic. The increase in generation of short-chain saturated fatty acids was favourable for the production of quality biodiesel. [ABSTRACT FROM AUTHOR]

The marine eustigmatophyte Nannochloropsis is one of the potential producers of eicosapentaenoic acid (EPA), a valued nutraceutical. Nannochloropsis sp. was cultivated under photoautotrophic condition utilizing CO 2 in a two phase cultivation process in order to enhance the eicosapentaenoic acid (EPA) productivity. It was cultivated in a photobioreactor up to late log phase for cell growth (phase I). Then, the culture was harvested and confronted to relatively low temperature (10 °C) and low light (30 μmol photons m −2 s −1 ) in both photobioreactor and Erlenmeyer flask (phase II), thus augmenting EPA% by 3.4 fold. Lower temperature with low light favored the synthesis of EPA although, biomass productivity, lipid content and lipid productivity were slightly decreased relative to phase I. The total lipids extracted from Nannochloropsis sp. fractionated into neutral lipids (NLs), glycolipids (GLs) and phospholipids (PLs) and a major proportion of EPA was found in phospholipids. Results suggested that low temperature and low light may ameliorate partitioning towards EPA in phospholipids. [ABSTRACT FROM AUTHOR]

The aim of the present study was to find out the optimum sodium bicarbonate concentration to produce higher biomass with higher lipid and carbohydrate contents in microalgae Scenedesmus sp. CCNM 1077. The role of bicarbonate supplementation under different nutritional starvation conditions was also evaluated. The results clearly indicate that 0.6 g/L sodium bicarbonate was optimum concentration resulting in 20.91% total lipid and 25.56% carbohydrate along with 23% increase in biomass production compared to normal growth condition. Addition of sodium bicarbonate increased the activity of nutrient assimilatory enzymes, biomass, lipid and carbohydrate contents under different nutritional starvation conditions. Nitrogen starvation with bicarbonate supplementation resulted in 54.03% carbohydrate and 34.44% total lipid content in microalgae Scenedesmus sp. CCNM 1077. These findings show application of bicarbonate grown microalgae Scenedesmus sp. CCNM 1077 as a promising feedstock for biodiesel and bioethanol production. [ABSTRACT FROM AUTHOR]

A 2-kW continuous ultrasonic flow system (UFS) was found effective in the disruption of two microalgal strains: Scenedesmus dimorphus and Nannochloropsis oculata . Compared to the control, cell debris concentration of UFS treatments increased up to 202% for S. dimorphus and 112% for N. oculata. Similarly, Nile red stained lipid fluorescence density (NRSLD) increased up to 59.5% and 56.3% for S. dimorphus and N. oculata , respectively. It was also found that increasing ultrasound intensity improved cell disruption efficiency indicated by up to 54% increase in NRSLFD of the two strains. Increasing sonication-processing time to 3-min resulted in 33.0% increase for S. dimorphus and 45.7% increase for N. oculata in NRSLFD compared to the control. Cell recirculation was found beneficial to cell disruption, however, higher initial cell concentration significantly reduced cell disruption efficiency, indicated by 98.2% decrease in NRSLFD per cell when initial cell concentration increased from 4.25 × 10 6 to 1.7 × 10 7 cells ml −1 . [ABSTRACT FROM AUTHOR]

Microbial lipids produced by oleaginous yeasts serve as promising alternatives to traditional oils and fats for the production of biodiesel and oleochemicals. To improve its techno-economics, it is pivotal to use wastes and produce high quality lipids of special fatty acid composition. In the present study, four oleaginous yeasts were tested to use free fatty acids for lipid production under non-growth conditions. Microbial lipids of exceptionally high fatty acid relative contents, e.g. those contained over 70% myristic acid or 80% oleic acid, were produced that may be otherwise inaccessible by growing cells on various carbon sources. It was found that Cryptococcus curvatus is a robust strain that can efficiently use oleic acid as well as even-numbered saturated fatty acids with carbon atoms ranging from 10 to 20. Our results provided new opportunity for the production of functional lipids and for the exploitation of organic wastes rich in free fatty acids. [ABSTRACT FROM AUTHOR]

Extracting lipids from oleaginous microbial cells in a cost effective and environmentally compatible manner remains a critical challenge in developing manufacturing paradigms for advanced liquid biofuels. In this study, a new approach using microbial growth inhibitors from lignocellulose-derived feedstocks was used to extract lipids efficiently from wet cell mass of the oleaginous bacterium Rhodococcus opacus MITXM-61. Nine common lignocellulose-derived inhibitors for treatment of cells prior to solvent extraction were used and evaluated for their efficiency of lipid extraction from the cells. When the inhibitors were individually examined, formic acid and furfural showed the highest extraction efficiency of lipids from wet cell mass. Multiple extractions of lipids with methanol from wet cell mass pretreated with combined common inhibitors or hardwood hydrolysate comprising lignocellulose-derived inhibitors resulted in lipid recovery of greater than 85% of total lipids, a 1.7-fold increase of lipid extraction as compared to those in the absence of the inhibitors. [ABSTRACT FROM AUTHOR]

Chlorella vulgaris , a marine microalgae strain adaptable to 0–50 g L −1 of salinity, was selected for studying the coupling system of saline wastewater treatment and lipid accumulation. The effect of total nitrogen (TN) concentration was investigated on algal growth, nutrients removal as well as lipid accumulation. The removal efficiencies of TN and total phosphorus (TP) were found to be 92.2–96.6% and over 99%, respectively, after a batch cultivation of 20 days. To illustrate the response of lipid accumulation to nutrients removal, C. vulgaris was further cultivated in the recycling experiment of tidal saline water within the photobioreactor. The lipid accumulation was triggered upon the almost depletion of nitrate (<5 mg L −1 ), till the final highest lipid content of 40%. The nitrogen conversion in the sequence of nitrate, nitrite, and then to ammonium in the effluents was finally integrated with previous discussions on metabolic pathways of algal cell under nitrogen deficiency. [ABSTRACT FROM AUTHOR]

Methods to convert microalgal biomass to bio based fuels and chemicals are limited by several processing and economic hurdles. Research conducted in this study modified/optimized a previously published procedure capable of extracting transesterifiable lipids from wet algal biomass. This optimization resulted in the extraction of 77% of the total transesterifiable lipids, while reducing the amount of materials and temperature required in the procedure. In addition, characterization of side streams generated demonstrated that: (1) the C/N ratio of the residual biomass or lipid extracted (LE) biomass increased to 54.6 versus 10.1 for the original biomass, (2) the aqueous phase generated contains nitrogen, phosphorous, and carbon, and (3) the solid precipitate phase was composed of up to 11.2 wt% nitrogen (70% protein). The ability to isolate algal lipids and the possibility of utilizing generated side streams as products and/or feedstock material for downstream processes helps promote the algal biorefinery concept. [ABSTRACT FROM AUTHOR]