Abstract
Microalgae are important microorganisms which produce potentially valuable compounds. Astaxanthin, a group of xanthophyll carotenoids, is one of the most powerful antioxidants mainly found in microalgae, yeasts, and crustaceans. Environmental stresses such as intense light, drought, high salinity, nutrient depletion, and high temperature can induce the accumulation of astaxanthin. Thus, this research aims to investigate the effect of black light, also known as long-wave ultraviolet radiation or UV-A, as a stressor on the accumulation of astaxanthin as well as to screen the antioxidant property in two tropical green algal strains isolated from Malaysia, Coelastrum sp. and Monoraphidium sp. SP03. Monoraphidium sp. SP03 showed a higher growth rate (0.66 day−1) compared to that of Coelastrum sp. (0.22 day−1). Coelastrum sp. showed significantly higher accumulation of astaxanthin in black light (0.999 g mL culture−1) compared to that in control condition (0.185 g mL−1). Similarly, Monoraphidium sp. SP03 showed higher astaxanthin content in black light (0.476 g mL culture−1) compared to that in control condition (0.363 g mL culture−1). Coelastrum sp. showed higher scavenging activity (30.19%) when cultured in black light condition, indicating a correlation between the antioxidant activity and accumulation of astaxanthin. In this study, black light was shown to possess great potential to enhance the production of astaxanthin in microalgae.
Highlights
Microalgae are important microorganisms which produce potentially valuable compounds
The results indicated that both Coelastrum sp. (Fig. 5A) and Monoraphidium sp
Coelastrum sp. that belong to the family of Scenedesmacea and Monoraphidium sp
Summary
Microalgae are important microorganisms which produce potentially valuable compounds. Microalgae can be classified as prokaryotic and eukaryotic organisms that are mostly found in the aquatic environment These organisms possess unique characteristics of higher plants (oxygenic photosynthesis) combined with biotechnological attributes such as fast growth rates, ease of cultivation and the ability to accumulate primary and secondary m etabolites[1,2]. Astaxanthin, a group of xanthophyll carotenoids is recognized as one of the most powerful antioxidants found in nature that has been noted to surpass those of β-carotene and α-tocopherol (vitamin E)[5] It is a red fat-soluble pigment found mainly in microalgae, yeast, and some crustaceans and gained. Antioxidants are compounds that can neutralize the reactive oxygen species (ROS) and other free radicals that generated by various metabolic processes and environmental stresses such as smoke, air pollution and UV damage
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