Microalgae and some of their uses

 

      Microalgae refer to a large group of fast-growing unicellular or simple multicellar microorganisms that use photosynthesis to transform CO2 and sunlight into biomass with oxygen and water vapor as byproducts. Microalgae cells in general have a high content of lipids and can be the sustainable source of microalgae oil. To pursue new and high-value applications of microalgae oil will be beneficial to the microalgae industry.Three fabrication methods are adopted, and the formation of vesicles/carriers or nanoemulsions from microalgae oil is confirmed. By using a mechanical dispersion method, vesicles with well controlled sizes and high physical stability can be fabricated from microalgae oil. The applicability of the fabrication method is revealed by using microalgae oils with different fatty acid compositions as the raw materials. Encapsulation ability of the microalgae oil-based vesicles is then demonstrated by using lutein, which is an unsaturated polyenic hydrocarbons, composed of eight isoprene residues forming the carbon chain with 40 carbon atoms and two hydroxyl groups in β-ion rings (lutein is physiologically delivered to the retina, and it has been thought to protect the retina by reducing the cytotoxic influence of light stimuli by blocking blue light and by suppressing ROS as an antioxidant. However, whether lutein administration reduces ROS in the retina under disease conditions that are independent of light exposure was unclear until the report of Sasaki et al..Sasaki et al. showed that, in the STZ-induced diabetes model, including lutein as a constant component of the diet significantly reduced the intensity of DHE(dihydroethidium) staining in the neural retina, without reducing the blood sugar level, as the model nutritious supplement. With the probe sonication method, stable microalgae oil-based carriers can be easily prepared even at a low temperature of 20°C. Encapsulation capability of the microalgae oil-based carriers is then shown by using vitamin E acetate as the model compound. Microalgae oil-based nanoemulsions with high physical stability can be fabricated by adopting a homogenization-extrusion method with the potential of being scaled up.

      Microalgae harvesting methods are generally not efficient and cost-effective due to the inherent characteristics of microalgae. These problems can be addressed by membrane technology for effective microalgae harvesting and nutrient removal. Microalgae are commonly rich in lipids, protein, and carbohydrates. Many of them are cultivated for feed, food, and biofuel production. Appropriate pre-treatment including wall-breaking, separation, and extraction, must first be adopted to extract protein, lipids, and polysaccharides from microalgae cells, so as to fully use the microalgal biomass. Operational parameters (i.e., hydraulic retention time, light conditions, etc.) should be optimized to obtain better performance. Alginate-immobilized microalgae beads and solid carriers accelerate microalgae growth and mitigate membrane fouling by the adsorption and degradation of foulants. A membrane bioreactor combined with microalgae photobioreactor effectively treats various types of wastewaters and enhances microalgae cultivation. Membrane modification and in situ physical cleaning methods (i.e., patterned membrane, turbulent jet-assisted microfiltration, etc.) remove foulants from the membrane surface and improve membrane permeability, thereby reducing the specific energy demand and harvesting cost. Microalgae culture using wastewater and exhausts can achieve the dual purpose of improving the environment and obtaining high value-added microalgae biomass, which has a promising application prospect such as in the field of sewage treatment and carbon emission reduction, and has already been the focus of people’s attention.

 

Reference

Microalgae oil-based drug delivery systems: Fabrication and applications, Biomass, Biofuels, and Biochemicals

Lutein and Oxidative Stress-Mediated Retinal Neurodegeneration in Diabetes, Diabetes: Oxidative Stress and Dietary Antioxidants