A Review on the Assessment of Stress Conditions for Simultaneous Production of Microalgal Lipids and Carotenoids

Abstract

Microalgal species are potential resource of both biofuels and high-value metabolites, and their production is growth dependent. Growth parameters can be screened for the selection of novel microalgal species that produce molecules of interest. In this context our review confirms that, autotrophic and heterotrophic organisms have demonstrated a dual potential, namely the ability to produce lipids as well as value-added products (particularly carotenoids) under influence of various physico-chemical stresses on microalgae. Some species of microalgae can synthesize, besides some pigments, very-long-chain polyunsaturated fatty acids (VL-PUFA,>20C) such as docosahexaenoic acid and eicosapentaenoic acid, those have significant applications in food and health. Producing value-added by-products in addition to biofuels, fatty acid methyl esters (FAME), and lipids has the potential to improve microalgae-based biorefineries by employing either the autotrophic or the heterotrophic mode, which could be an offshoot of biotechnology. The review considers the potential of microalgae to produce a range of products and indicates future directions for developing suitable criteria for choosing novel isolates through bioprospecting large gene pool of microalga obtained from various habitats and climatic conditions.

An overview of the utilisation of microalgae biomass derived from nutrient recycling of wet market wastewater and slaughterhouse wastewater

“…and Scenedesmus sp. had an increased production of carbohydrates under similar conditions (Minhas et al 2016). Hence, to optimise the production of biomass alongside with high lipid yields, microalgae should be cultivated in nitrogen rich conditions for high production of biomass yield and then transferred to low nitrogen conditions for lipid production.…”

“…Riano et al (2016) indicated that C.sorokinianabiomass produced 3.0-4.5% dry matter from nitrogen uptakes, whereas the nitrogen content in biomass cells ranged from 27 to 40%. The nitrogen levels in wastewater affect microalgae lipid production and growth rates by 1-10% (Minhas et al 2016) as high concentrations of nitrogen might increase the quantity of microalgae biomass. In contrast, the production of lipid and carbohydrates increases when there is nitrogen deficiency.…”

“…Moreover, pH factor is one of the many factors, which has more influence on microalgae growth. For example, temperature is a vital factor which has a linear relationship with microalgae growth, because it is able to modify growth rates and bio-product productivity (Huang et al 2008;Ras et al 2013;Minhas et al 2016). Effects of temperature include cellular chemical composition, rate of photosynthesis, nutrient uptake, CO 2 fixation, and respiration intensity (Tan et al 2009).…”

Exploitation of Microalgae Species for Nutraceutical Purposes: Cultivation Aspects

“…However, most microalgae prefer glucose as it can easily be assimilated and produce energy-rich compounds such as neutral lipids. Glucose-grown microalgae showed higher growth rates compared to those grown on acetate and fructose [68]. The yield of lutein was found to be increased with the increase in glucose concentration in C. protothecoides [69].…”

“…However, to reduce the cost and also to recycle industrial CO 2 , the microalgae cultivation facility should not be far away from the CO 2 source. (2) Heterotrophic cultivation: The organisms capable of heterotrophic cultivation lack the photosynthetic machinery and hence cannot generate energy through inorganic compounds oxidation [68]. Heterotrophic cultivation requires organic carbon (glucose, fructose, sucrose, lactose, galactose, mannose, acetate, glycerol, etc.)…”