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Energy security has become a serious global issue and a lot of research is being carried out to look for economically viable and environment-friendly alternatives. The only solution that appears to meet futuristic needs is the use of renewable energy. Although various forms of renewable energy are being currently used, the prospects of producing carbonneutral biofuels from microalgae appear bright because of their unique features such as suitability of growing in open ponds required for production of a commodity product, high CO 2 -sequestering capability, and ability to grow in wastewater/seawater/brackish water and high-lipid productivity. The major process constraint in microalgal biofuel technology is the cost-effective and efficient extraction of lipids. The objective of this article is to provide a comprehensive review on various methods of lipid extraction from microalgae available, to date, as well as to discuss their advantages and disadvantages. The article covers all areas of lipid extraction procedures including solvent extraction procedures, mechanical approaches, and solvent-free procedures apart from some of the latest extraction technologies. Further research is required in this area for successful implementation of this technology at the production scale.

An economic and environmentally friendly approach of overcoming the problem of fossil CO 2 emissions would be to reuse it through fixation into biomass. Carbon dioxide (CO 2 ), which is the basis for the formation of complex sugars by green plants and microalgae through photosynthesis, has been shown to significantly increase the growth rates of certain microalgal species. Microalgae possess a greater capacity to fix CO 2 compared to C 4 plants. Selection of appropriate microalgal strains is based on the CO 2 fixation and tolerance capability together with lipid potential, both of which are a function of biomass productivity. Microalgae can be propagated in open raceway ponds or closed photobioreactors. Biological CO 2 fixation also depends on the tolerance of selected strains to high temperatures and the amount of CO 2 present in flue gas, together with SO x and NO x . Potential uses of microalgal biomass after sequestration could include biodiesel production, fodder for livestock, production of colorants and vitamins. This review summarizes commonly employed microalgal species as well as the physiological pathway involved in the biochemistry of CO 2 fixation. It also presents an outlook on microalgal propagation systems for CO 2 sequestration as well as a summary on the life cycle analysis of the process.

Enzymatic and non-enzymatic antioxidant potentials of Chlorella vulgaris have gained considerable importance in recent decades. C. vulgaris strain highly tolerant to extreme pH variations was isolated and mass-cultivated in the wastewater from a confectionery industry. C.vulgaris showed better growth in wastewater than in improvised CFTRI medium. The microalgal biomass was then screened for the following antioxidants: peroxidase, superoxide dismutase, polyphenol oxidase, glutathione peroxidase, chlorophyll a, ascorbic acid, α-tocopherol and reduced glutathione. The total polyphenol content of the strain was also studied. The strain showed a high degree of enzymatic antioxidant activity (0.195 × 10(-5) ± 0.0072 units/cell peroxidase, 0.04125 × 10(-5) ± 0.001 units/cell superoxide dismutase, 0.2625 × 10(-5) ± 0.003 units/cell polyphenol oxidase and 0.025 × 10(-5) ± 0.003 glutathione peroxidase). The microalgal biomass also showed, per milligram weight, 0.2182 ± 0.005 μg of ascorbic acid, 0.00264 ± 0.001 μg of α-tocopherol and 0.07916 ± 0.004 μg of reduced glutathione. These results represent the possibility of using C. vulgaris grown in confectionery industry wastewater as a source of nutritious supplement, which is highly promising in terms of both economic and nutritional point of view.