Algae are fast growing biomass and can be converted to Biodiesel fuel. The demand of biodiesel is growing worldwide. Microalgae need a light:dark regime for productive photosynthesis. Light conditions and Temperature affect directly the growth rate of microalgae (duration and intensity).Literature review of some Green algae species Chlorella, Spirogyra, Chlamydomonas, Botryococcus, Scenedesmus, Neochloris, Haematococcus, Nannochloropsis, Ulva species and few species of brown algae, red algae, blue green algae were chosen to study the effect of temperature and light intensity on their growth. Optimum temperature range 20 °C to30 °C was observed for growth of different algae species. Light irradiance varies between 33 µmol m−2 s−1 to 400 µmol m−2 s−1. Maximum growth rate was found 1.73 d−1 for Selenastrum minutum at 35 °C and 420 µmol m−2 s−1 irradiance. Minimum growth rate (0.10 d−1) was reported for Botryococcus braunii KMITL 2 strain at temperature 25 °C, photoperiod 24:0 and 200 µmol m−2 s−1 irradiance.

Effect of temperature and light on the growth of algae species: A review

Omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) provide significant health benefits and this has led to an increased consumption as dietary supplements. Omega-3 fatty acids EPA and DHA are found in animals, transgenic plants, fungi and many microorganisms but are typically extracted from fatty fish, putting additional pressures on global fish stocks. As primary producers, many marine microalgae are rich in EPA (C20:5) and DHA (C22:6) and present a promising source of omega-3 fatty acids. Several heterotrophic microalgae have been used as biofactories for omega-3 fatty acids commercially, but a strong interest in autotrophic microalgae has emerged in recent years as microalgae are being developed as biofuel crops. This paper provides an overview of microalgal biotechnology and production platforms for the development of omega-3 fatty acids EPA and DHA. It refers to implications in current biotechnological uses of microalgae as aquaculture feed and future biofuel crops and explores potential applications of metabolic engineering and selective breeding to accumulate large amounts of omega-3 fatty acids in autotrophic microalgae.

https://researchonline.jcu.edu.au/28112/1/Microalgal_biofactories_a_promising_approach.pdf

Microalgal biofactories: a promising approach towards sustainable omega-3 fatty acid production

Microalgae represent a potential source of renewable nutrition and there is growing interest in algae-based dietary supplements in the form of whole biomass, e.g., Chlorella and Arthrospira, or purified extracts containing omega-3 fatty acids and carotenoids. The commercial production of bioactive compounds from microalgae is currently challenged by the biorefinery process. This review focuses on the biochemical composition of microalgae, the complexities of mass cultivation, as well as potential therapeutic applications. The advantages of open and closed growth systems are discussed, including common problems encountered with large-scale growth systems. Several methods are used for the purification and isolation of bioactive compounds, and many products from microalgae have shown potential as antioxidants and treatments for hypertension, among other health conditions. However, there are many unknown algal metabolites and potential impurities that could cause harm, so more research is needed to characterize strains of interest, improve overall operation, and generate safe, functional products.

Microalgae for High-Value Products Towards Human Health and Nutrition.

http://www.everythingconnects.org/uploads/7/0/3/5/7035190/jellyfish_blooms_in_china.pdf

Jellyfish blooms in China: dominant species, causes and consequences.

The production, characterization, and antioxidant capacity of the carotenoid fucoxanthin from the marine diatom Odontella aurita were investigated. The results showed that low light and nitrogen-replete culture medium enhanced the biosynthesis of fucoxanthin. The maximum biomass concentration of 6.36 g L−1 and maximum fucoxanthin concentration of 18.47 mg g−1 were obtained in cultures grown in a bubble column photobioreactor (O 3.0 cm inner diameter), resulting in a fucoxanthin volumetric productivity of 7.96 mg L−1 day−1. A slight reduction in biomass production was observed in the scaling up of O. aurita culture in a flat plate photobioreactor, yet yielded a comparable fucoxanthin volumetric productivity. A rapid method was developed for extraction and purification of fucoxanthin. The purified fucoxanthin was identified as all-trans-fucoxanthin, which exhibited strong antioxidant properties, with the effective concentration for 50% scavenging (EC50) of 1,1-dihpenyl-2-picrylhydrazyl (DPPH) radical and 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radical being 0.14 and 0.03 mg mL−1, respectively. Our results suggested that O. aurita can be a natural source of fucoxanthin for human health and nutrition.

https://www.mdpi.com/1660-3397/11/7/2667/pdf

Production, Characterization, and Antioxidant Activity of Fucoxanthin from the Marine Diatom Odontella aurita

A new chrysolaminarin, named CL2, with a molecular mass of 7.75 kDa, was purified from the marine diatom, Odontella aurita, using DEAE-52 cellulose anion-exchange chromatography and Sephadex G-200 gel-filtration chromatography. The monosaccharide and structural analysis revealed that CL2 was a glucan mainly composed of glucose, which was linked by the β-d-(1→3) (main chain) and β-d-(1→6) (side chain) glycosidic bond, demonstrated by infrared spectroscopy (IR) and nuclear magnetic resonance (NMR). The antioxidant activity tests revealed that the CL2 presented stronger hydroxyl radical scavenging activity with increasing concentrations, but less was effective on reducing power analysis and scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The influences of nitrogen concentration and light intensity on chrysolaminarin production of O. aurita were further investigated in a glass column photobioreactor, and a record high chrysolaminarin productivity of 306 mg L−1 day−1 was achieved. In conclusion, the chrysolaminarin CL2 from O. aurita may be explored as a natural antioxidant agent for application in aquaculture, food and pharmaceutical areas.

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Preliminary Characterization, Antioxidant Properties and Production of Chrysolaminarin from Marine Diatom Odontella aurita

Effects of temperature, salinity and irradiance on the growth of the harmful dinoflagellate Prorocentrum donghaiense Lu.

The marine diatom Phaeodactylum tricornutum is a polymorphological, ecologically significant, and well-studied model of unicellular microalga. This diatom can accumulate diverse important metabolites. Herein, we cultured P. tricornutum in an internally installed tie-piece flat-plate photobioreactor under 14.5 m mol L−1 (high nitrogen, HN) and 2.9 m mol L−1 (low nitrogen, LN) of KNO3 and assessed its time-resolved changes in biochemical compositions. The results showed that HN was inductive to accumulate high biomass (4.1 g L−1). However, the LN condition could accelerate lipid accumulation in P. tricornutum. The maximum total lipid (TL) content under LN was up to 42.5% of biomass on day 12. Finally, neutral lipids (NLs) were 63.8% and 75.7% of TLs under HN and LN, respectively. The content of EPA ranged from 2.3% to 1.5% of dry weight during the growth period under the two culture conditions. Peak volumetric lipid productivity of 128.4 mg L−1d−1 was achieved in the HN group (on day 9). The highest volumetric productivity values of EPA, chrysolaminarin, and fucoxanthin were obtained in the exponential phase (on day 6) under HN, which were 9.6, 93.6, and 4.7 mg L−1d−1, respectively. In conclusion, extractable amounts of lipids, EPA, fucoxanthin, and chrysolaminarin could be obtained from P. tricornutum by regulating the culture conditions.

Co-production of lipids, eicosapentaenoic acid, fucoxanthin, and chrysolaminarin by Phaeodactylum tricornutum cultured in a flat-plate photobioreactor under varying nitrogen conditions

The cultivation of microalgae is a high energy consumption process, which consumes a large amount of water, nutrients, electric energy and manpower. Thus, comprehensive utilization of algal biomass is a key to achieving cost-effective industrial production of bioproducts. In this paper, an integrated biorefinery process was conducted on Phaeodactylum tricornutum biomass to produce three valuable bioactive compounds via stepwise extraction using different solvent systems. Fucoxanthin, highly concentrated eicosapentaenoic acid (EPA), and chrysolaminarin were successively purified, concentrated, and characterized from P. tricornutum with a series of separation and identification technologies, and the yield (the weight of the purified compounds/the absolute weight in algal biomass, %) of these active compounds were 34.03 ± 0.72%, 23.00 ± 0.29%, and 43.54 ± 0.91%, respectively. Moreover, the fucoxanthin extraction conditions were also optimized, and ethanol and microwave-assisted treatments of 1 min provided the best fucoxanthin yield. In conclusion, this study suggested an effective biorefinery process for the production of fucoxanthin, EPA, and chrysolaminarin from the same P. tricornutum biomass.

An integrated biorefinery process: Stepwise extraction of fucoxanthin, eicosapentaenoic acid and chrysolaminarin from the same Phaeodactylum tricornutum biomass

Storage triacylglycerol accumulated by oleaginous microalgae have been utilized as optimal feedstock for biodiesel production. Nitrogen limitation is one of the most effective approaches in inducing oil accumulation in microalgae. However, the mechanism underlying this process is not well established. The aim of the present study was to determine changes in morphology, growth, biochemical composition, and photosynthetic performance of Chlorella vulgaris JNU13 under low nitrogen supply (LN, 3.5 mM) and high nitrogen supply (HN, 17.6 mM). The results showed that LN repressed cell division and cell weight gain. C. vulgaris under HN showed higher lipid levels compared to those subjected to LN. LN showed a decrease in photosynthetic capacity [relative electron transport rate (rETR), photosynthetic oxygen evolution rate (P-n), and utilization efficiency of light energy (alpha)], ratio of PS I to PS II, dark respiration rate (R-d), and the proportion of z-scheme electron transport pathway. Inversely, LN increased the proportion of the alternative electron transport pathway and non-photochemical quenching (NPQ). The damaged photosystems during limited nitrogen conditions negatively affected lipid accumulation in oleaginous C. vulgaris JNU13. It is therefore essential to maintain a balance between low nitrogen stress and high photosynthetic capacity by regulating the initial nitrogen supply to maximize lipid yield. The results of the present study may be used as a reference for regulating the initial nitrogen supply to enhance oil productivity. (C) 2016 Published by Elsevier B.V.

Morphology, growth, biochemical composition and photosynthetic performance of Chlorella vulgaris (Trebouxiophyceae) under low and high nitrogen supplies

Chengwu Zhang

Papers

Preliminary Characterization, Antioxidant Properties and Production of Chrysolaminarin from Marine Diatom Odontella aurita

Effects of temperature, salinity and irradiance on the growth of the harmful dinoflagellate Prorocentrum donghaiense Lu.

Co-production of lipids, eicosapentaenoic acid, fucoxanthin, and chrysolaminarin by Phaeodactylum tricornutum cultured in a flat-plate photobioreactor under varying nitrogen conditions

An integrated biorefinery process: Stepwise extraction of fucoxanthin, eicosapentaenoic acid and chrysolaminarin from the same Phaeodactylum tricornutum biomass

Morphology, growth, biochemical composition and photosynthetic performance of Chlorella vulgaris (Trebouxiophyceae) under low and high nitrogen supplies