Indigenous Algae Research Articles

Experimental evaluation of Scenedesmus javanensis, Halochlorella rubescens, and Chlorolobion braunii for lipid-rich biomass production and phycoremediation of dairy wastewater

Phycoremediation uses algae as an ecotechnological tool to recycle eutrophic and polluted wastewater from industries. It is vital for fostering a sustainable circular bioeconomy, as the resulting algal biomass can be utilized as a versatile industrial bioresource. This approach is especially pertinent for the dairy industry, which produces substantial amounts of nutrient-rich dairy wastewater (DWW). The effectiveness of phycoremediation of DWW depends on the knowledge of indigenous algae that can thrive in such conditions and rapidly produce lipid-rich or nutraceutically or otherwise valuable biomass. This study assessed the lab-scale phycoremediation of DWW, emphasizing the biomass production potential and quality of three fast-growing green microalgae: Chlorolobion braunii, Scenedesmus javanensis, and Halochlorella rubescens, which are recognized for their high lipid yield potential in growth media. We assessed nutrient and mineral removal efficiency, biomass yield, productivity, biomass quality, and the biodiesel properties of lipids from these algae after ten days of growth in various dilutions and 100 % DWW. C. braunii demonstrated the highest biomass productivity of 149.32 mg L−1 d−1 in 100 % DWW. All species significantly reduced biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total dissolved solids (TDS) of DWW, achieving complete removal of nutrients, along with 80–100 % removal of heavy metals after growth in DWW. C. braunii had a lipid productivity of 49.79 mg L−1 d−1 in 100 % DWW, and lipids from C. braunii and S. javanensis were suitable for biodiesel production, highlighting their potential for large-scale industrial phycoremediation of DWW while generating biodiesel-grade lipids and other valuable bioproducts.

Distribution, screening and biochemical characterization of indigenous microalgae for bio-mass and bio-energy production potential from three districts of Pakistan.

Trend of biofuel production from microalgal triacylglycerols is enhancing, because this substrate is a good sustainable and advantageous alternative to oil and gas fuel. In the present study, indigenous micro algal isolates were screened from water (n=30) and soil (n=30) samples collected from three districts of Punjab, Pakistan to evaluate their biofuel production potential. The samples were inoculated on BG - 11 agar medium plates by incubating at room temperature of 25°C providing 1000 lux for 16h light cycle followed by 8h of dark cycle for 15 d. Water samples were found to be rich in microalgae and 65.33% microalgae (49 isolates) were isolated from Faisalabad district. On the basis of microscopic morphology microalgal isolates (n=180) were selected and subjected to lipid detection by Nile red staining assay. Nile red positive isolates (n=23) were processed for biochemical (lipid, protein and carbohydrates) characterization. AIN63 isolate showed higher lipids (17.4%) content as detected by micro vanillin assay. Algal isolate AIN128 showed best protein contents (42.91%) detected by Bradford assay and AIN172 isolate showed higher carbohydrate contents (73.83%) as detected by anthrone assay. The selected algal isolates were also analyzed by Fourier transform infrared (FTIR) spectroscopy for confirmation of carbohydrate, protein and lipid analysis. These indigenous algae have the potential for in-vitro biofuel production from agricultural waste.

Soil health improvement by inoculation of indigenous microalgae in saline soil.

Using biological methods to improve saline soils is recognized as an eco-friendly and sustainable way. In this study, two indigenous algae YJ-1 and YJ-2 screened from salinized farmland were inoculated into saline soils with different salinization levels to investigate their potential in enhancing soil health by laboratory microcosm experiment. The results showed that individual inoculation of the two algae quickly resulted in the formation of algal crusts, and the chlorophyll content in the saline soils gradually increased with the incubation time. The soil pH decreased significantly from the initial 8.15-9.45 to 6.97-7.56 after 60-day incubation. The exopolysaccharides secretion and the activities of catalase, sucrase, and urease in saline soils also increased. Microalgal inoculation increased soil organic matter storage, while decreasing the available nutrient contents possibly due to the depletion of microalgal growth. PCA and PCC results identified that microalgal biomass as the predominant variable affecting soil quality. Overall, these data revealed the great potential of microalgae in the amelioration of saline soils, especially in pH reduction and enzyme activity enhancement. This study will provide the theoretical foundation for improving saline soils via algalization.

Bioaccumulation of metals by algae from acid mine drainage: a case study of Frongoch Mine (UK)

In Frongoch Mine (UK), it is unclear the distribution of metals on indigenous algae and whether these species of algae can accumulate metals. This study aimed to investigate the role of indigenous algae for metal removal from acid mine drainage and understand if metals can be adsorbed on the surface of algae or/and bioaccumulated in algae. A sequential extraction procedure was applied for algae samples collected from acid mine drainage (AMD) water to identify the forms in which metals are found in algae. Concentrations of Fe, Pb, Zn, Cu and Cd were evaluated in the algae and AMD samples were collected in June and October 2019. AMDs samples had a pH value ranging between 3.5 and 6.9 and high concentrations of Zn (351 mg/L) and Pb (4.22 mg/L) that exceeded the water quality standards (Water Framework Directive, 2015). Algae Ulothrix sp. and Oedogonium sp. were the two main species in the Frongoch AMDs. The concentrations of metals in algae ranged from 0.007 to 51 mg/g, and the bioconcentration factor of metals decreased in the following order: Fe > > Pb > > Cu > Cd > Zn. It was found that Zn, Cu and Cd were adsorbed onto the surface of and bioaccumulated in the algae, while Pb and Fe were mainly bioaccumulated in the algae. Indigenous algae can be considered as a biogeochemical barrier where metals are accumulating and can be used in bioremediation methods. Also, indigenous algae could be used as a bioindicator to assess water pollution at Frongoch Mine and other similar metal mines.

Insights into the potential impact of algae-mediated wastewater beneficiation for the circular bioeconomy: A global perspective

Algae-based technologies are one of the emerging solutions to societal issues such as accessibility to clean water and carbon-neutral energy and are a contender for the circular bioeconomy. In this review, recent developments in the use of different algal species for nutrient recovery and biomass production in wastewater, challenges, and future perspectives have been addressed. The ratio and bioavailability of nutrients in wastewater are vital parameters, which significantly impact nutrient recovery efficiency and algal biomass production. However, the optimum nutrient concentration and ratio may vary depending upon the microalgal species as well as cultivation conditions. The use of indigenous algae and algae-based consortia with other microorganisms has been proved promising in improving nutrient recovery efficiency and biomass production in pilot scale operations. However, environmental and cultivation conditions also play a significant role in determining the feasibility of the process. This review further focused on the assessment of the potential benefits of algal biomass production, renewable biofuel generation, and CO2 sequestration using wastewater in different countries on the basis of available data on wastewater generation and estimated nutrient contents. It was estimated that 5–10% replacement of fossil crude requirement with algal biofuels would require ~952–1903 billion m3 of water, 10–21 billion tons of nitrogen, and 2–4 billion tons of phosphorus fertilizers. In this context, coupling wastewater treatment and algal biomass production seem to be the most sustainable option with potential global benefits of polishing wastewater through nutrients recycling and carbon dioxide sequestration.

Evaluation of copper toxicity using site specific algae and water chemistry: Field validation of laboratory bioassays

Studies of metal toxicity to microalgae have predominantly been conducted using single non-target algae species and without due regard for the chemistry of the treated waters, leading to ineffective or excessive algaecide treatments. In this study, indigenous multi-algal species (Scenedesmus quadricauda, and Scenedesmus subspicatus and Oscillatoria agardhii) were used in laboratory toxicity bioassays under simulated field water chemistry (pH = 7.2, hardness = 196 mg L−1 as CaCO3, and alkalinity = 222 mg L−1 as CaCO3) to determine the optimum copper sulfate treatment dose to control algae growth in an irrigation canal. Toxicity bioassays were conducted using copper sulfate in chelated (with EDTA) and non-chelated (without EDTA) forms to assess the influence of the use of synthetic chelators in toxicity studies. Also, copper toxicity to the indigenous algae species was measured in the non-modified EPA test medium (pH = 7.5, hardness = 92 mg L−1 as CaCO3, alkalinity = 10 mg L−1 as CaCO3 and EDTA= 300 µg L−1) to assess the impact of the water chemistry on algae inhibitory algal dosages. Under simulated water chemistry conditions, lower toxicity was measured in the test flasks with the chelated form of copper (96 h- EC50= 386.67 µg L−1 as Cu) as compared to those with the non-chelated metal (96 h-EC50= 217.17 µg L−1 as Cu). In addition, higher copper toxicity was measured in the test flasks prepared with the non-modified EPA medium using chelated copper (96 h-EC50 = 65.93 µg L−1 as Cu) as compared to their analogous microcosms with modified water chemistry (96 h-EC50= 386.67 µg L−1 as Cu), the increased water hardness and alkalinity in the latter case contributing to the decrease of the metal bioavailability. Results from laboratory experiments showed good correlation with copper dosages used in a small scale field testing to control algae growth, increasing confidence in laboratory bioassays.

Evaluation of antioxidant activity and total phenol content of Gracilaria bursa-pastoris harvested in Nador lagoon for an enhanced economic valorization

BackgroundThe Gracilaria bursa-pastoris is an abundant alga that is responsible for the eutrophication in Nador lagoon in Morocco. Therefore, the lagoon is a deposit of bioresources whose economic value can be enhanced. Antioxidative properties of seaweed extracts have been studied in several geographic regions, but only a few studies have been performed on tropical seaweed species, and no research has been done to determine antioxidant activity and valorization of the indigenous algae in Nador lagoon in Morocco.MethodsThe present study evaluated the antioxidant potential of methanolic and aqueous extracts from Gracilaria bursa-pastoris by measuring the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and total content of phenolic, flavonoids and flavonols content in each extract.ResultsThis study showed that this macroalgae contained a high total phenolic content (142.26 and 79.43 mg GAE g−1 extract) for ethanolic and aqueous extracts, respectively. All extracts exhibited a DPPH radical scavenging activity, and the methanolic extracts demonstrated a great antioxidant potential with very low value of EC50 (0.085 mg/mL), significantly equivalent to EC50 (0,028 mg/mL) of commercial antioxidant ascorbic acid. These results suggest that the macroalgae have a great antioxidant potential which could be considered for future applications in medicine, food production or cosmetic industry in Morocco.ConclusionsThis work showed that the ethanolic extract was rich in phenolic compounds. This extract exhibited the highest antioxidant activity which may be explained by the presence of a large quantity of phenolic compounds. The Gracilaria bursa-pastoris can be utilized as a source of natural antioxidant compounds.

Evaluation of phenotype stability and ecological risk of a genetically engineered alga in open pond production

Genetically engineered (GE) algae offer the promise of producing food, fuel, and other valuable products with reduced requirements for land and fresh water. While the gains in productivity measured in GE terrestrial crops are predicted to be mirrored in GE algae, the stability of phenotypes and ecological risks posed by GE algae in large-scale outdoor cultivation remain unknown. Here, we describe the first US Environmental Protection Agency (EPA)-sanctioned experiment aimed at understanding how GE algae perform in outdoor cultivation. Acutodesmus dimorphus was genetically engineered by the addition of two genes, one for enhanced fatty acid biosynthesis, and one for recombinant green fluorescence protein (GFP) expression; both the genes and their associated phenotypes were maintained during fifty days of outdoor cultivation. We also observed that while the GE algae dispersed from the cultivation ponds, colonization of the trap ponds by the GE strain declined rapidly with increasing distance from the source cultivation ponds. In contrast, many species of indigenous algae were found in every trap pond within a few days of starting the experiment. When inoculated in water from five local lakes, the GE algae's effect on biodiversity, species composition, and biomass of native algae was indiscernible from those of the wild-type (wt) progenitor algae, and neither the GE nor wt algae were able to outcompete native strains. We conclude that GE algae can be successfully cultivated outdoors while maintaining GE traits, and that for the specific GE algal strain tested here they did not outcompete or adversely impact native algae populations when grown in water taken from local lakes. This study provides an initial evaluation of GE algae in outdoor cultivation and a framework to evaluate GE algae risks associated with outdoor GE algae production.

Effects of episodic sediment resuspension on phytoplankton in Lake Taihu: focusing on photosynthesis, biomass and community composition

Sediment resuspension is an important characteristic of large shallow lakes. To further understand the influence of sediment resuspension on the nutrients release, the algal photosynthetic activity, algal biomass and algal community composition, a 2 × 5 factorial (2 water types and 5 turbulence intensities) bioassay experiment was carried out for 2 weeks. 2 water types: one type water was filtered through GF/F filter to remove all indigenous algae (Filtered group) and the other type was source water without filtering through GF/F filter (Non-filtered group). 5 turbulence intensities in the experiment simulated the different intensity of the field wind-induced turbulence in Lake Taihu, with different turbidities (0, 30, 70, 150, 250 NTUs). Results showed that sediment resuspension had significant effects on the nutrients release that could be absorbed to support algae growing. Different turbulence intensities had no significant effects on the photosynthetic activities. The time variation of photosynthetic parameters in the Filtered and Non-filtered groups indicated that algae could moderate themselves to adapt to different intensities turbulence environment to be more in favor of photosynthesis. In addition, sediment resuspension also brought sediment-associated algae back into the water body increasing the algal biomass. The community composition in the Filtered group and Non-filtered group showed that the new phytoplankton community formed from the resuspended algae was similar to the original community. So, the research highlights the importance of sediment resuspension in long-term management goals and restoration efforts for these types of ecosystems.

Biostimulation of Oil Sands Process-Affected Water with Phosphate Yields Removal of Sulfur-Containing Organics and Detoxification.

The ability to mitigate toxicity of oil sands process-affected water (OSPW) for return into the environment is an important issue for effective tailings management in Alberta, Canada. OSPW toxicity has been linked to classical naphthenic acids (NAs), but the toxic contribution of other acid-extractable organics (AEOs) remains unknown. Here, we examine the potential for in situ bioremediation of OSPW AEOs by indigenous algae. Phosphate biostimulation was performed in OSPW to promote the growth of indigenous photosynthetic microorganisms and subsequent toxicity and chemical changes were determined. After 12 weeks, the AEO fraction of phosphate-biostimulated OSPW was significantly less toxic to the fission yeast Schizosaccharomyces pombe than unstimulated OSPW. Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) analysis of the AEO fraction in phosphate-biostimulated OSPW showed decreased levels of SO3 class compounds, including a subset that may represent linear arylsulfonates. A screen with S. pombe transcription factor mutant strains for growth sensitivity to the AEO fraction or sodium dodecylbenzenesulfonate revealed a mode of toxic action consistent with oxidative stress and detrimental effects on cellular membranes. These findings demonstrate a potential algal-based in situ bioremediation strategy for OSPW AEOs and uncover a link between toxicity and AEOs other than classical NAs.

Algae biomass cultivation in nitrogen rich biogas digestate.

Because microalgae are known for quick biomass growth and nutrient uptake, there has been much interest in their use in research on wastewater treatment methods. While many studies have concentrated on the algal treatment of wastewaters with low to medium ammonium concentrations, there are several liquid waste streams with high ammonium concentrations that microalgae could potentially treat. The aim of this paper was to test ammonium tolerance of the indigenous algae community of Lake Mälaren and to use this mixed consortia of algae to remove nutrients from biogas digestate. Algae from Lake Mälaren were cultivated in Jaworski's Medium containing a range of ammonium concentrations and the resulting algal growth was determined. The algae were able to grow at NH4-N concentrations of up to 200 mg L(-1) after which there was significant inhibition. To test the effectiveness of the lake water algae on the treatment of biogas digestate, different pre-cultivation set-ups and biogas digestate concentrations were tested. It was determined that mixing pre-cultivated suspension algae with 25% of biogas digestate by volume, resulting in an ammonium concentration of around 300 mg L(-1), produced the highest algal growth. The algae were effective in removing 72.8±2.2% of NH4-N and 41.4±41.4% of PO4-P.

Open pond cultures of indigenous algae grown on non-arable land in an arid desert using wastewater

The algae production on non-arable land in the al-Wusta region of the Sultanate of Oman was evaluated. Pre-cleaned production water (pPW) from the oil production was enriched with nutrients and used as growth medium. The indigenous isolate Scenedesmus sp. MKB was grown in open ponds under semi-continuous conditions. A productivity of 16.1 g/m2/day in 2013 and 15.4 g/m2/day in 2014 was reached during four different experiments during March and April of 2013 and 2014. Thereby, no influences of light intensity (maximum daily values in between 2400 and 3050 µmol photons/m2/s) or temperature (maximum daily temperatures were between 29.9 and 41.9 °C) on productivity were observed (correlation coefficient below ±0.5). Weed algae, mainly Cyanobacteria and diatoms were detected microscopically in all cultures by the first to seventh day of growth. The increase in weed algae had a negative influence on the maximum photosynthetic efficiency (Y). Y decreased after a weed algae concentration of ca. 2 % (cell/cell) was reached.

In situ biodegradation of naphthenic acids in oil sands tailings pond water using indigenous algae–bacteria consortium

In this study, the biodegradation of total acid-extractable organics (TAOs), commonly called naphthenic acids (NAs), was investigated. An indigenous microbial culture containing algae and bacteria was taken from the surface of a tailings pond and incubated over the course of 120days. The influence of light, oxygen and the presence of indigenous algae and bacteria, and a diatom (Navicula pelliculosa) on the TAO removal rate were elucidated. The highest biodegradation rate was observed with bacteria growth only (without light exposure) with a half-life (t1/2) of 203days. The algae–bacteria consortium enhanced the detoxification process, however, bacterial biomass played the main role in toxicity reduction. Principal component analysis (PCA) conducted on FT-IR spectra, identified functional groups and bonds (representing potential markers for biotransformation of TAOs) as follows: hydroxyl, carboxyl and amide groups along with CH, arylH, arylOH and NH bonds.

Bioethanol Production from Indigenous Algae

Enhanced rate of fossil fuel extraction is likely to deplete limited natural resources over short period of time. So search for alternative fuel is only the way to overcome this problem of upcoming energy crisis. In this aspect biofuel is a sustainable option. Agricultural lands cannot be compromised for biofuel production due to the requirement of food for the increasing population. Certain species of algae can produce ethanol during anaerobic fermentation and thus serve as a direct source for bioethanol production. The high content of complex carbohydrates entrapped in the cell wall of the microalgae makes it essential to incorporate a pre-treatment stage to release and convert these complex carbohydrates into simple sugars prior to the fermentation process. There have been researches on production of bioethanol from a particular species of algae, but this work was an attempt to produce bioethanol from easily available indigenous algae. Acid hydrolysis was carried out as pre-treatment. Gas Chromatographic analysis showed that 5 days’ fermentation by baker’s yeast had yielded 93% pure bioethanol. The fuel characterization of the bioethanol with respect to gasoline showed comparable and quite satisfactory results for its use as an alternative fuel.DOI: http://dx.doi.org/10.3126/ije.v4i1.12182International Journal of Environment Volume-4, Issue-1, Dec-Feb 2014/15, page: 112-120

Effect of pH and Temperature on the Efficiency of Indigenous Algae to Remove Contaminants from Artificial Wastewaters

A series of Lab incubation experiments were conducted to assess the effect of different pHs (5.5., 7.0 and 8.5) and temperature ranges (25, 30 and 35 0 C) on the ability of indigenous algal species for removal of contaminants and other heavy metals, from artificial contaminated water during 2012-13. For this purpose, algal samples were collected from different areas in district Buner. Artificial contaminated waters were prepared and amended to pH 5.5, 7.0 or 8.5 using dilute alkali or acid and then each set was inoculated with mix culture of Microspora, Navicula, Chaetophora, Spirogyra, Apanothece, and Hydrodictyon as these were most abundant and common algal species in Buner. After inoculation, each set was incubated at 25, 30 or 35 o C for 10 days. The results obtained on the efficiency of indigenous algae collected from Buner to remove contaminants and other heavy metals from artificial wastewaters under different pH levels (5.5, 7.0 and 8.5) and temperature ranges (25, 30 and 35 0 C) showed that a mix culture of algae viz., Microspora, Navicula, Chaetophora, Spirogyra, Apanothece, and Hydrodictyon removed variable amount of heavy metals ranged from 37 % in case of Cu up to 96 % in case of Ni from wastewaters. The results revealed that change in pH between 5.5 and 8.5 and in temperature between 25 and 35 0 C had no remarkable influence on the efficiency of algae to remove these elements from contaminated water.

Assessing the toxicity of organophosphorous pesticides to indigenous algae with implication for their ecotoxicological impact to aquatic ecosystems

This study aimed to determine the toxicity of three organophosphorous pesticides, chlorpyrifos, terbufos and methamidophos, to three indigenous algal species isolated from local rivers and algal mixtures. The diatom Nitzschia sp. (0.30–1.68 mg L−1 of EC50 -the estimated concentration related to a 50% growth reduction) and the cyanobacteria Oscillatoria sp. (EC50 of 0.33–7.99 mg L−1) were sensitive to single pesticide treatment and the chlorophyta Chlorella sp. was the most tolerant (EC50 of 1.29–41.16 mg L−1). In treatment with the mixture of three pesticides, Chlorella sp. became the most sensitive alga. The antagonistic joint toxic effects on three indigenous algae and algal mixtures were found for most of the two pesticide mixtures. The results suggested that mixture of pesticides might induce the detoxification mechanisms more easily than the single pesticide. The synergistic interactions between terbufos and methamidophos to algal mixtures and between methamidophos and chlorpyrifos to Nitzschia sp. indicated methamidophos might act as a potential synergist. Differential sensitivity of three families of algae to these pesticides might result in changes in the algal community structures after river water has been contaminated with different pesticides, posing great ecological risk on the structure and functioning of the aquatic ecosystem.

Ultrasound Frequency Impacts on the Removal of Indigenous Blue-Green Algae Taken from Lake Taihu

This paper studied the ultrasonic removal of indigenous blue-green algae taken from Lake Taihu. The results showed that higher ultrasound frequency benefited the removal of indigenous algae. But in consideration of complex condition of the natural lakes and reservoirs such as the lack of powerful electrical supply system, low sound frequency is more suitable. Because of slightly improvement in the algae removal rate constants among the low frequency range (20-100 kHz), 20 kHz is the best ultrasound frequency for indigenous algae removal. Moreover, little change in the microcystins concentration was found with sonication at 20 kHz, 2W for 60s, which was compared with the increased microcystins from 2.67 to 2.851 mg/L after sonication at 1000 kHz, 2W for 60s. the concentration of chlorophyll.

Indigenous algae for local bioresource production: Phycoprospecting

Photosynthetic algae represent a large and diverse group of organisms that have only a limited history of characterization and exploitation. The application of resource production from algae is relatively untapped, with the potential to produce fuels, food, fibers and nutraceuticals on a large scale. Methods to screen for indigenous species of algae have improved and can allow communities to prospect for algae suited to regional needs. When cultured locally, indigenous algae are adapted to the prevailing regional abiotic and biotic factors. Native algae commonly inhabit local waste resources and pose no risk of becoming noxious invasives. Methods for culturing algae can utilize anthropogenic waste resources including wastewater nutrients and CO 2 from fossil fuel combustion. While genetic engineering may have a role in helping future algae production succeed, the majority of algae species have yet to be identified or characterized and the genetic diversity of these unknown species may offer significant but currently unknown benefits for bioresource production. Recalcitrant problems of culture stability, biomass density, harvesting, and product refining may be overcome by exploring native biological material. Selecting indigenous algae with intrinsic characteristics amenable to bioresource production and waste mitigation – phycoprospecting – is the most sustainable path forward for widespread algae-based bioresource development. Our recent efforts in phycoprospecting of local habitats revealed a diversity of algae with significant lipid content.

Cultivation of algae with indigenous species – Potentials for regional biofuel production

The massive need for sustainable energy has led to an increased interest in new energy resources, such as production of algae, for use as biofuel. There are advantages to using algae, for example, land use is much less than in terrestrial biofuel production, and several algae species can double their mass in 1 day under optimized conditions. Most algae are phototrophs and some are nitrogen-fixing. Algae production therefore requires only small amounts of amendments such as carbon sources and nutrients. In the present paper an experiment was performed using water sampled from Lake Mälaren in Sweden. The lake water is considered nutrient rich, has relatively neutral pH and is rich in organic compounds and suspended solids. The idea behind this research was to enhance indigenous algae production rather than inoculate new species into the system. A simple experimental setup was designed where algae biomass growth was measured regularly over a 13 day period. FT-IR absorption spectra were evaluated in order to determine protein, lipid, carbohydrate and silicate contents of the algae. The algae community structure was characterized throughout the production cycle. Furthermore, the potential for energy supply for the transportation sector in the Mälardalen region from algae cultivated as tested in the experiment was evaluated.

Isolation and Characterization of Taiwanese Heterotrophic Microalgae: Screening of Strains for Docosahexaenoic Acid (DHA) Production

Marine heterotrophic microalgal species which are potentially rich in docosahexaenoic acid (DHA, C22:6n-3) have been found in Taiwan; however, there was a lack of detailed analysis and characterization of these indigenous algae which is needed for the development of commercial applications. Hence, the objective of this study was to screen DHA-rich heterotrophic microalgae species indigenous to Taiwan for commercial purposes. Heterotrophic microalgae from a variety of marine habitats were isolated, cultivated, and then identified according to their 18S rRNA gene sequences and morphological characteristics. A comparison was made of their fatty acid profiles, fatty acid content, and amount of biomass. For the strain with highest DHA yield, the optimal growth conditions were determined in order to establish the best fermentation conditions for scale-up. In this study, 25 heterotrophic microalgal strains were successfully isolated from marine habitats around Taiwan. All of the isolated strains showed a close phylogenic relationship with the Thraustochytriaceae family according to their 18S rRNA gene sequences. GC/MS analysis discerned seven distinctive fatty acid profiles of these strains, with the production of eicosapentaenoic acid (C20:5n-3) ranging from 0.02 to 2.61 mg L(-1), and DHA ranging from 0.8 to 18.0 mg L(-1). An Aurantiochytrium strain BL10 with high DHA production was subsequently chosen for further manipulation. Under optimal growth conditions it could produce up to 59.0 g of dry biomass per liter of culture, with dry biomass containing 73% total fatty acid and 29% DHA, revealing BL10 as an excellent source of microbial DHA.