Process Engineering for High-Cell-Density Cultivation of Lipid Rich Microalgal Biomass of <Emphasis Type="Italic">Chlorella</Emphasis> sp. FC2 IITG

In the present study, process engineering strategy was applied to achieve lipid-rich biomass with high density of Chlorella sp. FC2 IITG under photoautotrophic condition. The strategy involved medium optimization, intermittent feeding of limiting nutrients, dynamic change in light intensity, and decoupling growth and lipid induction phases. Medium optimization was performed using combinations of artificial neural network or response surface methodology with genetic algorithm (ANN-GA and RSM-GA). Further, a fed-batch operation was employed to achieve high cell density with intermittent feeding of nitrate and phosphate along with stepwise increase in light intensity. Finally, mutually exclusive biomass and lipid production phases were decoupled into two-stage cultivation process: biomass generation in first stage under nutrient sufficient condition followed by lipid enrichment through nitrogen starvation. The key findings were as follows: (i) ANN-GA resulted in an increase in biomass titer of 157 % (0.95 g L^?1) in shake flask and 42.8 % (1.0 g L^?1) in bioreactor against unoptimized medium at light intensity of 20 μE m^?2 s^?1; (ii) further optimization of light intensity in bioreactor gave significantly improved biomass titer of 5.6 g L^?1 at light intensity of 250 μE m^?2 s^?1; (iii) high cell density of 13.5 g L^?1 with biomass productivity of 675 mg L^?1 day^?1 was achieved with dynamic increase in light intensity and intermittent feeding of limiting nutrients; (iv) finally, two-phase cultivation resulted in biomass titer of 17.7 g L^?1 and total lipid productivity of 313 mg L^?1 day^?1 which was highest among Chlorella sp. under photoautotrophic condition.     

Lipid productivity and fatty acid composition in Chlorella and Scenepdesmus strains grown in nitrogen-stressed conditions

Thirty Chlorella and 30 Scenedesmus strains grown in nitrogen-stressed conditions (70 mg L^?1 N) were analyzed for biomass accumulation, lipid productivity, protein, and fatty acid (FA) composition. Scenedesmus strains produced more biomass (4.02?±?0.73 g L^?1) after 14 days in culture compared to Chlorella strains (2.57?±?0.12 g L^?1). Protein content decreased and lipid content increased from days 8 to 14 with an increase in triacylglycerol (TAG) accumulation in most strains. By day 14, Scenedesmus strains generally had higher lipid productivity (53.5?±?3.7 mg lipid L^?1 day^?1) than Chlorella strains (35.1?±?2.8 mg lipid L^?1 day^?1) with the lipids consisting mainly of C16–18 TAGs. Scenedesmus strains generally had a more suitable FA profile with higher amounts of saturated fatty acids and monounsaturated fatty acids (MUFAs) and a smaller polyunsaturated fatty acid (PUFA) component. Chlorella strains had a larger PUFA component and smaller MUFA component. The general trend in the FA composition of Chlorella strains was oleic > palmitic > α-linolenic = linoleic > eicosenoic > heptadecenoic > stearic acid. For Scenedesmus strains, the general trend was oleic > palmitic > linoleic > α-linolenic > stearic > eicosenoic > palmitoleic > heptadecenoic acid. The most promising strains with the highest lipid productivity and most suitable FA profiles were Scenedesmus sp. MACC 401, Scenedesmus soli MACC 721, and Scenedesmus ecornis MACC 714. Although Chlorella sp. MACC 519 had lower lipid productivity, the FA profile was good with a lower PUFA component compared to the other Chlorella strains analyzed and a low linolenic acid concentration.     

Nutrient removal from high strength nitrate containing industrial wastewater using <Emphasis Type="Italic">Chlorella</Emphasis> sp. strain ACUF_802

the research aim of this study was to characterize an isolated native strain of Chlorella sp. ACUF_802, well adapted to a high nitrate concentration environment and to investigate its potential to nitrate and phosphate removal from industrial wastewaters with the minimal addition of chemical reagents and energy. The isolated strain was identified and evaluated for its capability to support biomass growth and nutrient removal from synthetic wastewater in batch tests using different concentrations of carbon and nitrogen, different carbon sources and N:P ratios. The strain was isolated via the plating method from the settler of a pilot scale moving bed biofilm reactor performing a nitrification process. The strain was identified using molecular analysis with rDNA primers. Using sodium bicarbonate as carbon source, the batch productivity (71.43 mg L^?1 day^?1) of the strain Chlorella sp. ACUF_802 was calculated with a logistic model and compared to the values reported in the literature. Assays on the effect of the N:P ratio indicated that the productivity was increased 36% when the N:P ratio was close to 1 (111.96 mg L^?1 day^?1), but for a complete phosphorus removal a 5:1 N:P ratio with nitrate concentrations ≤125 mg?L^?1 is recommended. The isolated microalgae strain Chlorella sp. ACUF_802 showed versatility to grow in the synthetic industrial wastewaters tested and can be considered as an appropriate organism for nitrogen removal from industrial wastewaters in the presence of an organic or inorganic carbon source.     

Growth and nutrient removal of three macrophytes in response to concentrations and ratios of N and P

Wastewater from different sources shows great differences in concentrations and ratios of N and P. In order to choose suitable plant species to remove excess N and/or P from polluted waters, it is important to know the performances of these plants under different N and P concentrations. In this study, we investigated the growth and N and P removal rate of three macrophytes, Coix lacryma-jobi, Iris wilsonii, and Arundo donax under six N and P combination treatments. C. lacryma-jobi preferred higher N and P concentrations (16 mg N L^?1 and 3.2 mg P L^?1), and increasing N supply could increase its P removal rate. I. wilsonii exhibited a growth preference at a combination of moderate N and P concentrations (8 mg N L^?1 and 0.8 mg P L^?1). A. donax could grow well at all combinations of N and P and had significantly higher relative growth rate and N and P removal rates than the other two species. These results showed A. donax is a promising species to treat various polluted waters and the other two species can be used specifically to treat certain types of wastewater.     

Biomass and oil content of Chlorella sp., Haematococcus sp., Nannochloris sp. and Scenedesmus sp. under mixotrophic growth conditions in the presence of technical glycerol

The growth of algae strains Chlorella sp., Haematococcus sp., Nannochloris sp. and Scenedesmus sp. under mixotrophic conditions in the presence of different concentrations of technical glycerol was investigated with the aim of increasing biomass growth and algae oil content. The highest concentration of lipid obtained in media with 5 g L^?1 glycerol for Chlorella sp., Scenedesmus sp., Nannochloris sp. and Haematococcus sp. was 17.77, 22.34, 27.55 and 34.22 % larger than during the autotrophic growth of these species. Increases in triacylglycerols of up to ten times was observed for Scenedesmus sp. under mixotrophic conditions (using 10 g L^?1 glycerol), whereas an increase of 2.28 times was found for Haematococcus sp. The content of saturated fatty acids of Scenedesmus, Chlorella, Haematococcus and Nannochloris was 67.11, 34.63, 23.39 and 24.23 %, and the amount of unsaturated fatty acids was 32.9, 65.06, 79.61 and 75.78 % of total fatty acids, respectively. Growth on technical glycerol of these strains with light produced higher biomass concentrations and lipid content compared with autotrophic growth. The fatty acid content of oils from these species suggests their potential use as biodiesel feedstock.     

Triacylglycerol content,productivity and fatty acid profile in Scenedesmus acutus PVUW12

A detailed lipid characterization of Scenedesmus acutus PVUW12, with emphasis on the evaluation of triacylglycerols (TAGs) as a biodiesel feedstock, is presented. When algal cells were grown in nitrogen-free medium (N stress), a lipid increase was detected that was mainly due to TAG accumulation. In situ fluorescence measurements allowed the kinetics and extent of neutral lipid accumulation to be followed. Under N stress, the productivity of total lipids and TAGs increased significantly (80.99 and 63.74 mg L^?1 day^?1, respectively) compared with controls (29.51 and 16.23 mg L^?1 day^?1, respectively). Monounsaturated fatty acids were the major fraction and increased further (49.74 %) in stressed cells, with oleic acid as the most abundant compound (46.97 %). The polyunsaturated fatty acid composition of this algal oil appears to meet the European Standard EN 14214. These results indicate that S. acutus oil meets the requirements for its use as a biodiesel feedstock. Since this strain was also proposed for wastewater bioremediation, this opens up the possibility of its use in an integrated system combined with biofuel production.     

Inorganic carbon and pH effect on growth and lipid productivity of Tetraselmis suecica and Chlorella sp (Chlorophyta) grown outdoors in bag photobioreactors

There has been considerable interest in cultivation of green microalgae (Chlorophyta) as a source of lipid that can alternatively be converted to biodiesel. However, almost all mass cultures of algae are carbon-limited. Therefore, to reach a high biomass and oil productivities, the ideal selected microalgae will most likely need a source of inorganic carbon. Here, growth and lipid productivities of Tetraselmis suecica CS-187 and Chlorella sp were tested under various ranges of pH and different sources of inorganic carbon (untreated flue gas from coal-fired power plant, pure industrial CO₂, pH-adjusted using HCl and sodium bicarbonate). Biomass and lipid productivities were highest at pH 7.5 (320?±?29.9 mg biomass L^?1 day^?1and 92?±?13.1 mg lipid L^?1 day^?1) and pH 7 (407?±?5.5 mg biomass L^?1 day^?1 and 99?±?17.2 mg lipid L^?1 day^?1) for T. suecica CS-187 and Chlorella sp, respectively. In general, biomass and lipid productivities were pH 7.5?>?pH 7?>?pH 8?>?pH 6.5 and pH 7?>?pH 7.5?=?pH 8?>?pH 6.5?>?pH 6?>?pH 5.5 for T. suecica CS-187 and Chlorella sp, respectively. The effect of various inorganic carbon on growth and productivities of T. suecica (regulated at pH?=?7.5) and Chlorella sp (regulated at pH?=?7) grown in bag photobioreactors was also examined outdoor at the International Power Hazelwood, Gippsland, Victoria, Australia. The highest biomass and lipid productivities of T. suecica (51.45?±?2.67 mg biomass L^?1 day^?1 and 14.8?±?2.46 mg lipid L^?1 day^?1) and Chlorella sp (60.00?±?2.4 mg biomass L^?1 day^?1 and 13.70?±?1.35 mg lipid L^?1 day^?1) were achieved when grown using CO₂ as inorganic carbon source. No significant differences were found between CO₂ and flue gas biomass and lipid productivities. While grown using CO₂ and flue gas, biomass productivities were 10, 13 and 18 %, and 7, 14 and 19 % higher than NaHCO₃, HCl and unregulated pH for T. suecica and Chlorella sp, respectively. Addition of inorganic carbon increased specific growth rate and lipid content but reduced biomass yield and cell weight of T. suecica. Addition of inorganic carbon increased yield but did not change specific growth rate, cell weight or content of the cell weight of Chlorella sp. Both strains showed significantly higher maximum quantum yield (F_v/F_m) when grown under optimum pH.     

DETERMINATION OF METHYLENE BLUE BIOSORPTION BY Rhizopus arrhizus IN THE PRESENCE OF SURFACTANTS WITH DIFFERENT CHEMICAL STRUCTURES

Methylene blue (MB) biosorption properties of Rhizopus arrhizus were investigated in the presence of surfactants. The effects of cationic and anionic surfactants on MB removal by dead biomass (1 g L^?1) were determined. MB removal was tested as a function of initial pH (2–12), contact time (5–1440 min), and dye (37.4–944.7 mg L^?1) and surfactant (0–10 mM) concentrations. The opposite charged anionic surfactant dodecylbenzenesulfonic acid sodium salt (DBS) enhanced sorption of cationic MB by biomass dramatically. Maximum biosorption capacity was 471.5 mg g^?1 at pH 8 with 0.5 mM DBS at 944.7 mg L^?1 MB concentration. The surfactant-stimulated fungal decolorization method may provide a highly efficient, inexpensive, and time-saving procedure in biological wastewater treatment technologies.     

Applicability of one-stage partial nitritation and anammox in MBBR for anaerobically pre-treated municipal wastewater

Energy consumption of municipal wastewater treatment plants can be reduced by the anaerobic pre-treatment of the main wastewater stream. After this pre-treatment, nitrogen can potentially be removed by partial nitritation and anammox (PN/A). Currently, the application of PN/A is limited to nitrogen-rich streams (>500 mg L^?1) and temperatures 25–35 °C. But, anaerobically pretreated municipal wastewater is characterized by much lower nitrogen concentrations (20–100 mg L^?1) and lower temperatures (10–25 °C). We operated PN/A under similar conditions: total ammonium nitrogen concentration 50 mg L^?1 and lab temperature (22 °C). PN/A was operated for 342 days in a 4 L moving bed biofilm reactor (MBBR). At 0.4 mg O₂ L^?1, nitrogen removal rate 33 g N m^?3 day^?1 and 80 % total nitrogen removal efficiency was achieved. The capacity of the reactor was limited by low AOB activity. We observed significant anammox activity (40 g N m^?3 day^?1) even at 12 °C, improving the applicability of PN/A for municipal wastewater treatment.     

Complete and simultaneous removal of ammonium and m-cresol in a nitrifying sequencing batch reactor

The kinetic behavior, oxidizing ability and tolerance to m-cresol of a nitrifying sludge exposed to different initial concentrations of m-cresol (0–150 mg C L^?1) were evaluated in a sequencing batch reactor fed with 50 mg NH₄ ⁺-N L^?1 and operated during 4 months. Complete removal of ammonium and m-cresol was achieved independently of the initial concentration of aromatic compound in all the assays. Up to 25 mg m-cresol-C L^?1 (C/N ratio of 0.5), the nitrifying yield (Y-NO₃ ^?) was 0.86 ± 0.05, indicating that the nitrate was the main product of the process; no biomass growth was detected. From 50 to 150 mg m-cresol-C L^?1 (1.0 ≤ C/N ≤ 3.0), simultaneous microbial growth and partial ammonium-to-nitrate conversion were obtained, reaching a maximum microbial total protein concentration of 0.763 g L^?1 (247 % of its initial value) and the lowest Y-NO₃ ^? 0.53 ± 0.01 at 150 mg m-cresol-C L^?1. m-Cresol induced a significant decrease in the values of both specific rates of ammonium and nitrite oxidation, being the ammonium oxidation pathway the mainly inhibited. The nitrifying sludge was able to completely oxidize up to 150 mg m-cresol-C L^?1 by SBR cycle, reaching a maximum specific removal rate of 6.45 g m-cresol g^?1 microbial protein-N h^?1. The number of SBR cycles allowed a metabolic adaptation of the nitrifying consortium since nitrification inhibition decreased and faster oxidation of m-cresol took place throughout the cycles.     

Growth and turion formation of Potamogeton crispus in response to different phosphorus concentrations in water

The vegetative growth and turion formation of Potamogeton crispus, a submersed aquatic macrophyte, was investigated under a range of phosphorus (P) concentrations (0.025, 0.25, 2.5 and 25 mg P L^?1) in the ambient water free of algae, aiming to identify the responses of submersed aquatic macrophytes to nutrient enrichment, a common eutrophication problem in China and worldwide. Plant growth was not affected by different P concentrations in terms of biomass accumulation of stems and leaves. However, the contents of chlorophyll a and starch in plants decreased with increasing water P levels, whereas chlorophyll b and carotenoids declined with P level ranging from 0.025 to 2.5 mg P L^?1. The soluble sugar content decreased when water P concentration increased up to 2.5 mg L^?1. The P content in plants increased with increasing water P levels, whereas plant N content decreased and soluble protein increased when water P concentration increased over 0.25 mg L^?1, implying that P. crispus may have modified its metabolism to adapt to water P availability. When P concentration increased to 25 mg L^?1, the number and dry matter production of turions per plant decreased significantly. Meanwhile, there was a significant reduction in turion weight and the accumulations of soluble sugar and starch in turion, when water P concentration was over 0.25 mg L^?1. The results suggest that turion formation in P. crispus is sensitive to P concentration in the ambient water, and high P levels may lead to decreases in P. crispus populations due to the decline in turion production.     

Elicitor mediated enhancement of wedelolactone in cell suspension culture of <Emphasis Type="Italic">Eclipta alba</Emphasis> (L.) Hassk

The present research focused on enhancing the production of wedelolactone through cell suspension culture (CSC) in Eclipta alba (L.) Hassk. With an aim of attaining a sustainable CSC, various plant growth regulators, elicitors and agitation speed were examined. Nodal segments of in vitro propagated plantlets induced the maximum percentage (93.47?±?0.61%) of callus inoculated on Murashige and Skoog (MS) medium fortified with picloram (2 mg L^?1). The growth kinetics of CSC exhibited a sigmoid pattern with a lag phase (0–6 days), a log phase (6–18 days), a stationary phase (18–24 days) and then death phase thereafter. The highest biomass accumulation in CSC with 7.09?±?0.06 g 50 mL^?1 fresh weight, 1.52?±?0.02 g 50 mL^?1 dry cell weight, 1.34?±?0.01?×?10⁶ cell mL^?1 total cell count and 57.00?±?0.58% packed cell volume was obtained in the liquid MS medium supplemented with 1.5 mg L^?1 picloram plus 0.5 mg L^?1 kinetin at 120 rpm. High performance thin layer chromatography confirmed that yeast extract (biotic elicitor) at 150 mg L^?1 accumulated more CSC biomass with 1.22-fold increase in wedelolactone (288.97?±?1.94 µg g^?1 dry weight) content in comparison to the non-elicited CSC (237.78?±?0.04 µg g^?1 dry weight) after 120 h of incubation. Contrastingly, methyl jasmonate (abiotic elicitor) did not alter the biomass but increased the wedelolactone content (259.32?±?1.06 µg g^?1 dry weight) to an extent of 1.09-fold at 100 µM. Complete plantlet regeneration from CSC was possible on MS medium containing N⁶-benzyladenine (0.75 mg L^?1) and abscisic acid (0.5 mg L^?1). Thus, the establishment of protocol for CSC constitutes the bases for future biotechnological improvement studies in this crop.     

Long-term outdoor growth and lipid productivity of Tetraselmis suecica, Dunaliella tertiolecta and Chlorella sp (Chlorophyta) in bag photobioreactors

There has been considerable interest on cultivation of green microalgae (Chlorophyta) as a source of lipid that can alternatively be converted to biodiesel. The ideal microalga characteristics are that it must grow well even under high cell density and under varying outdoor environmental conditions and be able to have a high biomass productivity and contain a high oil content (~25–30 %). The main advantage of Chlorophyta is that their fatty acid profile is suitable for biodiesel conversion. Tetraselmis suecica CS-187 and Chlorella sp. were grown semi-continuously in bag photobioreactors (120 L, W?×?L?=?40?×?380 cm) over a period of 11 months in Melbourne, Victoria, Australia. Monthly biomass productivity of T. suecica CS-187 and Chlorella sp. was strongly correlated to available solar irradiance. The total dry weight productivity of T. suecica and Chlorella sp. was 110 and 140 mg L^?1 d^?1, respectively, with minimum 25 % lipid content for both strains. Both strains were able to tolerate a wide range of shear produced by mixing. Operating cultures at lower cell density resulted in increasing specific growth rates of T. suecica and Chlorella sp. but did not affect their overall biomass productivity. On the other hand, self shading sets the upper limit of operational maximum cell density. Several attempts in cultivating Dunaliella tertiolecta CS-175 under the same climatic conditions were unsuccessful.     

Efficiency of copper removal by Sargassum sinicola in batch and continuous systems

The efficiency of batch and continuous systems of copper removal by Sargassum sinicola was studied. The effects of flow rate, initial metal concentration, and bed density on the capacity of the continuous system were also recorded. In batch systems, the maximum biosorption capacity was calculated as 49.63?±?0.88 mg g^?1; in the continuous system, under the following conditions: flow rate of 10 mL min^?1, initial solution of 200 mg Cu L^?1, bed density of 150 g L^?1, and higher copper removal of 62.39?±?1.91 mg g^?1 was achieved. The Thomas model can be used to predict the breakthrough curves, but it underestimated breakthrough time.     

Optimization of culture conditions for the production of polysaccharides and kinsenoside from the rhizome cultures of <Emphasis Type="Italic">Anoectochilus roxburghii</Emphasis> (Wall.) Lindl.

The present study designed two sets of experiments by using the uniform design method and investigated the effects of medium components on the accumulation of bioactive compounds (polysaccharide and kinsenoside) in rhizomes, in order to select a suitable culture medium for the rhizome suspension culture of Anoectochilus roxburghii (Wall.) Lindl. Among the combinations of Murashige and Skoog (MS) medium strengths and plant growth regulator (benzylaminopurine, BA; kinetin, KT; and α-naphthaleneacetic acid, NAA) concentrations, and the combinations of nitrogen, phosphorus, and sucrose concentrations, the maximum yield of polysaccharides and kinsenoside was achieved with 0.75 × MS?+?2.0 mg L^?1 BA?+?0.2 mg L^?1 KT?+?0.5 mg L^?1 NAA and 45 mM nitrogen?+?0.93 mM phosphorus?+?35 g L^?1 sucrose, respectively. Therefore, the optimal rhizome suspension culture medium was 0.75 × MS medium supplemented with 2.0 mg L^?1 BA, 0.2 mg L^?1 KT, 0.5 mg L^?1 NAA, and 35 g L^?1 sucrose. Yeast extract (YE) enhanced bioactive compound accumulation in rhizomes. The polysaccharide and kinsenoside production was significantly improved when 75 mg L^?1 YE was added to the culture medium after 30 d of rhizome suspension culture; 8.3 g L^?1 of polysaccharide and 6.1 g L^?1 of kinsenoside were obtained after 4 d of YE treatment. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of YE-treated rhizomes was higher than that of YE-untreated rhizomes, demonstrating enhanced antioxidant activity of the treated bioreactor-cultured rhizomes.     

Carbon dioxide and poultry waste utilization for production of polyhydroxyalkanoate biopolymers by <Emphasis Type="Italic">Nostoc muscorum</Emphasis> Agardh: a sustainable approach

The new paradigm is to view wastes as resources for sustainable development. In this regard, the feasibility of poultry waste and CO₂ utilization for cultivation of a filamentous nitrogen-fixing cyanobacterium, Nostoc muscorum Agardh, was investigated for production polyhydroxyalkanoates, the biodegradable polymers. This cyanobacterium showed profound rise in biomass yield with up to 10 % CO₂ supply in airstream with an aeration rate of 0.1 vvm. Maximum biomass yield of 1.12 g L^?1 was recorded for 8 days incubation period, thus demonstrating a CO₂ biofixation rate of 0.263 g L^?1 day^?1 at 10 % (v/v) CO₂-enriched air. Poultry litter (PL) supplementation also had a positive impact on the biomass yield. The nutrient removal efficiency of N. muscorum was reflected in the significant reduction in nutrient load of PL over the experimental period. A maximum poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) [P(3HB-co-3HV)] copolymer yield of 774 mg L^?1 (65 % of dry cell wt.), the value almost 11-fold higher than the control, was recorded in 10 g L^?1 PL-supplemented cultures with 10 % CO₂ supply under the optimized condition, thus demonstrating that N. muscorum has good potential for CO₂ biomitigation and poultry waste remediation while simultaneously producing eco-friendly polymers.     

Potential Outdoor Cultivation of Green Microalgae Based on Response to Changing Temperatures and by Combining with Air Temperature Occurrence

In this study, our working hypothesis was to examine whether temperature alters biomass and metabolite production by microalgae according to strain. We also addressed whether it is possible to choose a strain suitable for growing in each season of a given region. A factorial experiment revealed a significant interaction between chlorophylls a and b (Chl a and Chl b), carotenoid/Chl (a?+?b) ratio, biomass and total lipid productivity of six green microalgae (four Chlorella spp., Chlorella sorokiniana and Neochloris oleoabundans) after 15 days at four temperatures. At 39/35 °C, two Chlorella sp. strains (IPR7115 and IPR7117) showed higher total carotenoids/Chl (a?+?b) (0.578 and 0.830), respectively. N. oleoabundans had the highest Chl a (8210 μg L^?1) and Chl b (1909 μg L^?1) at 19/15 °C and highest maximum dry biomass (2900 mg L^?1), specific growth rate (0.538 day^?1) and total lipids (1003 mg L^?1) at 15/8 °C. We applied a method to infer the growth of these six green microalgae in outdoor ponds, as based on their response to changing temperatures and by combining with historical data on day/night air temperature occurrence for a given region. We conclude that the use of regionalized maps based on air temperature is a good strategy for predicting microalgal cultivation in outdoor ponds based on their features and tolerance to changing temperature.     

Effects of Initial Phosphorus Concentration and Light Intensity on Biomass Yield per Phosphorus and Lipid Accumulation of Scenedesmus sp. LX1

Phosphorus has been considered as one of the most important limiting resources of large-scale production of microalgal biofuel. The approaches to increase biomass yield per phosphorus, along with the lipid accumulation properties of Scenedesmus sp. LX1, were investigated in this study. It was found that practical biomass yield per phosphorous was reduced with the increase of initial phosphorus (P) concentration, but increased with light intensity. The highest biomass yield per P of 4,500 kg-biomass/kg-P was achieved at initial phosphorus concentration of 0.05 mg?·?L^?1 under the light intensity of 320 μmol photon?·?m^?2?·?s^?1. Furthermore, the lipid content per biomass and triacylglycerols (TAGs) content per lipid were found to be positively correlated to biomass yield per P. With the biomass yield increased from 2,800 kg-biomass/kg-P to 4,500 kg-biomass/kg-P, the lipid content per microalgal biomass and TAG content per lipid increased from 18.7 % to 35.0 % and from 69.5 % to 83.0 %. These results suggested a possible approach to achieve high biomass production and high lipid content simultaneously.     

Lipid productivity and fatty acid composition-guided selection of Chlorella strains isolated from Malaysia for biodiesel production

The need to develop biomass-based domestic production of high-energy liquid fuels (biodiesel) for transportation can potentially be addressed by exploring microalgae with high lipid content. Selecting the strains with adequate oil yield and quality is of fundamental importance for a cost-efficient biofuel feedstock production based on microalgae. This work evaluated 29 strains of Chlorella isolated from Malaysia as feedstock for biodiesel based on volumetric lipid productivity and fatty acid profiles. Phylogenetic studies based on 18S rRNA gene revealed that majority of the strains belong to true Chlorella followed by Parachlorella. The strains were similarly separated into two groups based on fatty acid composition. Of the 18 true Chlorella strains, Chlorella UMACC187 had the highest palmitic acid (C16:0) content (71.3?±?4.2 % total fatty acids, TFA) followed by UMACC84 (70.1?±?0.7 %TFA), UMACC283 (63.8?±?0.7 %TFA), and UMACC001 (60.3?±?4.0 %TFA). Lipid productivity of the strains at exponential phase ranged from 34.53 to 230.38 mg L^?1 day^?1, with Chlorella UMACC050 attaining the highest lipid productivity. This study demonstrated that Chlorella UMACC050 is a promising candidate for biodiesel feedstock production.     

Changes in phytochemical content and pharmacological activities of three <Emphasis Type="Italic">Chlorella</Emphasis> strains grown in different nitrogen conditions

The phytochemical content and biological activity of three Chlorella strains cultured in low (35 mg L^?1) or high (700 mg L^?1) nitrogen (N) and harvested on days 5 and 10 were evaluated. High N resulted in a higher biomass in Chlorella MACC 438 and MACC 452 while MACC 555 produced a higher biomass in low N. MACC 555 (low N/day 5) had the highest phenolic content, and MACC 438 in low N/day 5 and high N/day 5 accumulated the highest flavonoids and condensed tannins, respectively. Iridoids were most abundant in MACC 452 on low N/day 10. Harvest time had the greatest effect on the phytochemical content with phenolics, flavonoids, and condensed tannins decreasing over time and iridoids increasing in low N and decreasing in high N conditions. Extracts were more active in β-carotene-linoleic acid model compared to 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. Most extracts had good antimicrobial activity. Extracts became less potent over time in the antioxidant, acetylcholinesterase inhibitory (AChE), and antimicrobial assays when growing in low N and more potent in the antioxidant and AChE assays when grown in high N. Thus, phytochemical content and biological activities of the three Chlorella strains were affected by N levels, harvest time, and strain.