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Omega-3 fatty acids containing microalgae are considered a promising feedstock for food and nutraceutical applications. To meet the commercial and nutritional demands of essential omega-3 fatty acids, different strategies are being implemented, including supplementation of plant growth regulators (PGRs). In the present study the effects of selected, PGRs, i.e., gibberellic acid (GA), and salicylic acid (SA), and malic acid (MA; TCA cycle intermediate), were studied on growth, lipid, and omega-3 fatty acid synthesis of Nannochloropsis oceanica CASA CC201. Significant increase in growth (10 ppm GA), a 1.9-fold increase in lipid production (40 ppm MA), and a 4-fold increase in EPA production by treatment with 10 ppm MA were found. To understand the mechanism behind significant changes in growth and metabolite production, we had analyzed the generation of oxidative stress, targeted metabolite, and amino acid profile of N. oceanica under PGR treatment. To elucidate the physiological role of key metabolic pathways and contribution to lipid synthesis, the targeted metabolites were selected from glycolysis, citric acid cycle, and pentose phosphate pathway. Metabolomics analysis revealed that there is a significant increase in ATP, NADPH, NADP, and NADH at cultures treated with high concentrations of selected PGRs and significant elevation of these metabolites are associated with increased lipid production.

Microalgae are unicellular photosynthetic organisms capable of producing high-value metabolites like carbohydrates, lipids, proteins, polyunsaturated fatty acids, vitamins, pigments, and other high-value metabolites. Microalgal biomass gained more interest for the production of nutraceuticals, pharmaceuticals, therapeutics, food supplements, feed, biofuel, bio-fertilizers, etc. due to its high lipid and other high-value metabolite content. Microalgal biomass has the potential to convert trapped solar energy to organic materials and potential metabolites of nutraceutical and industrial interest. They have higher efficiency to fix carbon dioxide (CO2) and subsequently convert it into biomass and compounds of potential interest. However, to make microalgae a potential industrial candidate, cost-effective cultivation systems and harvesting methods for increasing biomass yield and reducing the cost of downstream processing have become extremely urgent and important. In this review, the current development in different microalgal cultivation systems and harvesting methods has been discussed.

The aim of this study is to analyze the effect of two plant growth regulators on selective modulation of nutraceutically important fatty acids. Exogenous application of methyl jasmonate (MeJA) promoted microalgal growth compared to control. Treatment with 10 ppm salicylic acid (SA) induced significantly higher lipid production of 475 mg/L (2.2 fold). Interestingly treatment with higher doses of MeJA promoted monounsaturated fatty acid production, particularly oleic acid (C18:1) at early stationary growth phase, while treatment with SA induces essential omega 3 fatty acid production (EPA, C20:5). This significant modification of fatty acid compositions was correlated with the oxidative stress in terms of total reactive oxygen species production and endogenous growth hormone levels. Taken together, the results indicated that treatment with stress associated plant hormones significantly increased high value metabolite accumulation specifically MUFA and PUFA production by modulating stress mechanisms and endogenous growth hormone levels.

Two functionally different plant growth regulators, Kinetin and GA3, were evaluated individually or in combination for its effect on growth, lipid yield, PUFAs and EPA accumulation in Nannochloropsis oceanica CASA CC201 . It was observed that the treatment with 0.215 ppm Kinetin resulted in high cell number of 521 × 10 6 cells per mL than the control (398 × 10 6 cells per mL), but GA3 had an adverse effect on cell number. Kinetin increases the specific growth rate to 0.24/day and doubling time to 2.86 days than control (4.38 days). Treatment with GA3 at a concentration of 50 ppm gives the highest cellular lipid accumulation of 61.5% DCW than the control (35.5% DCW). The combination of Kinetin and GA3 exhibited a synergistic effect on total lipid yield of 246.25 mg/L compared with control (121.5 mg/L). The addition of Kinetin increases the percentage of EPA 4 times as compared to the control.

This review illustrated the role of metal-binding proteins (MBPs) and microbial interaction in assisting the phytoremediation of industrial wastewater polluted with heavy metals. MBPs are used to increase the accumulation and tolerance of metals by microorganisms via binding protein synthesis. Microbes have various protection mechanisms to heavy metals stress like compartmentalization, exclusion, complexity rendering, and the synthesis of binding proteins. MBPs include phytochelatins, metallothioneins, Cd-binding peptides (CdBPs), cysteines (gcgcpcgcg) (CP), and histidines (ghhphg)2 (HP). In comparison with other physico-chemical methods, phytoremediation is an eco-friendly and safe method for the society. The present review concentrated on the efficiency of phytoremediation strategies for the use of MBPs and microbe-assisted approaches.

The present study aims to evaluate the effect of different concentration of natural auxin, Indole-3 acetic acid (IAA) on growth, lipid yield, PUFA and EPA accumulation in Nannochloropsis oceanica CASA CC201. It was observed that the, treatment with 10ppm concentration of IAA resulted in high cell number 579.5×106cells/ml than the control (215.5×106cells/ml). Treatment with IAA at a concentration of 40ppm gives the highest cellular lipid accumulation of 60.9% DCW than the control 31.05% DCW). Lipid yield is also found to be increased by the addition of 40ppm IAA (319.5mg/L) compared with the control (121.5mg/L). EPA percentage is increased to 10.76% by the addition of 40ppm IAA compared to the control (1.87%).

Considering the rapid increase of world population and shrinking of arable land, algae could potentially serve as an alternate to supplement proteins and nutrients derived from terrestrial plants. Microalgae are rich in variety of nutritionally important compounds like proteins, pigments, carbohydrates, polyunsaturated fatty acids, dietary fibers and bioactive compounds with wide range of health benefits. Eicosapentaenoic acid and docosahexaenoic acid serve as wonder molecules by reducing the risk of cardiac diseases like arrhythmia, stroke, rheumatoid arthritis, and high blood pressure. Besides being used as nutritional source, microalgae are also widely used as natural colorant, pleasant aroma, and carrier molecules. Considering the health benefits of microalgae, World Health Organization declared Spirulina as one of the greatest superfood on the globe. This chapter presents the different nutraceuticals of micro- and macroalgae origin, its biochemical properties, and health benefits in a comprehensive manner.