Microalgae are used as food, feed, and fodder and also used to produce a wide range of metabolites such as, proteins, carbohydrates, lipids, carotenoids, vitamins, fatty acids, sterols, etc. They are able to enhance the nutritional content of conventional food and feed preparations and hence positively affect humans and animal health including aquaculture animals. They also provide a key tool for phycoremediation of toxic metals and nanometal production. The use of microalgae in nanotechnology is a promising fi eld of research with a green approach. The use of genetically modifi ed algae for better production of different biotechnological compounds of interests is popular nowadays. Microalgal biomass production for sustainable biofuel production together with other high-value compounds in a costeffective way is the major challenge of algal biotechnologists. Microalgal biotechnology is similar to conventional agriculture but has received quite a lot of attention over the last decades, because they can reach substantially higher productivities than traditional crops and can use the wastelands and the large marine ecosystem. As history has shown, research studies on microalgae have been numerous and varied, but they have not always resulted in commercial applications. The aim of this review is to summarize the commercial applications of microalgae.

A short term laboratory feeding trial was conducted to evaluate the importance of algae based value added feed for the popular ornamental fish Carassius auratus (Gold fish). The feed was tested against Daphnia -the conventional feed used for Goldfish. Fresh algal biomass of Nostoc ellipsosporum and Navicula minima were mixed with daphnia to formulate the value added feed and proximate composition of feeds were analyzed. The experimental feed showed significantly higher protein (71.24% ±0.3), lipid (33.47%±0.2), and carotenoid (6.41%±0.13) (Pd"0.05), and increased level of amino acids (4.2%±0.1) and carbohydrate (14.72%±0.2) content than the control feed. Similarly the fishes fed with experimental feed showed 2 fold increase in protein, glycogen and carotenoid level as compared to the control fishes. Morphometric study also showed significant Body weight Gain (3.52%±1.2) and Specific growth rate (0.87±0.41) together with high Protein Productive value (0.051±0.14), Protein effficiency ratio (0.074±0.05) and low Feed conversion ratio (0.024±0.03) in experimental fishes which signifies better utilization of feed by the fishes. The VAF (Value added feed) fed fishes showed positive results in both morphometry and carcass proximate composition. Differences in body weight gain and Feed conversion ratio together with increased protein, glycogen and carotenoid K O LK ATA RESEARCH ARTICLE levels were significant than the control fishes. The colouration of the gold fishes induced by algal carotenoids was more bright and vibrant indicating high market value.

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