Abstract
The aim of this study was to investigate the potential role of the microalga Chlamydomonas reinhardtii as an antioxidant source of enriched biomass. This microalga is a model organism deeply investigated for physiological studies, particularly considering carotenoid synthesis in response to stress, to counteract the effects of the formation of free radicals. Less attention has been paid to the profile characterization of other antioxidant compounds, such as polyphenols, which can be synthesized, concomitantly with carotenoids, under photooxidative stress, especially high light. The cultures of C. reinhardtii were exposed to three different light intensities, 70, 800 and 1500 µmoles photons m−2 s−1. The increasing light intensity symmetrically induced the increasing accumulation of both carotenoids and phenolic compounds. The results showed that exposure to high light intensities caused the accumulation of electrons in the electron transport chain, with a reduction in photosynthetic activity. In the same cultures, high light intensity induced the strong increment of polyphenols such as gallic, chlorogenic and coumaric acids, which resulted 6.2-fold, 4-fold and 3.7-fold higher, respectively, than in cells exposed to the lowest intensities. As expected, at the highest light intensity, the strong induction of the xanthophyll cycle and the largest increment of loroxanthin, lutein, α-carotene and ß-carotene could be detected. Antioxidant properties doubled with respect to the initial time, both in acetone and methanol cellular extracts of these cultures, revealing a new potential role for biotechnological application of this microalga.
Highlights
IntroductionInterest in the employment of antioxidants from natural sources is increasing considerably, due to the growing market demand for natural compounds and possible difficulties in the utilization of synthetic antioxidants and their possible toxic effects.Among the founts of natural compounds, microalgae biomass represents a good source of antioxidants, as microalgae are capable of high production of these metabolites (phenolic compounds, carotenoids, polyunsaturated fatty acids) under stress conditions, making increasingly important to focus attention on studying the physiology of these microorganisms [1,2,3]
Interest in the employment of antioxidants from natural sources is increasing considerably, due to the growing market demand for natural compounds and possible difficulties in the utilization of synthetic antioxidants and their possible toxic effects.Among the founts of natural compounds, microalgae biomass represents a good source of antioxidants, as microalgae are capable of high production of these metabolites under stress conditions, making increasingly important to focus attention on studying the physiology of these microorganisms [1,2,3]
Results showed that concerning the chlorophyll content, the most relevant and significant changes could be detected in C2 culture, as chlorophyll a, chlorophyll b and total chlorophyll concentrations were increased by 84%, 69%, and 79%, respectively
Summary
Interest in the employment of antioxidants from natural sources is increasing considerably, due to the growing market demand for natural compounds and possible difficulties in the utilization of synthetic antioxidants and their possible toxic effects.Among the founts of natural compounds, microalgae biomass represents a good source of antioxidants, as microalgae are capable of high production of these metabolites (phenolic compounds, carotenoids, polyunsaturated fatty acids) under stress conditions, making increasingly important to focus attention on studying the physiology of these microorganisms [1,2,3]. Under stress conditions— exposure to high light, nutrient limitation, or starvation—the photosynthetic efficiency decreases, with an increase in the reduction level of the electron transport chain. This condition promotes the photo-oxidative stress and 4.0/). Accumulation of excess energy, which induces photo-protective mechanisms, with the synthesis of antioxidants. Carotenoids are one of the most studied compounds, as they act both as a light-harvesting complex (LHC) and as photo-protectors. As xanthophylls and ß-carotene, are involved in photo-protection through the de-excitation of singlet chlorophyll (Chl), which accumulates in the LHC, especially under high light intensity, a well-studied mechanism in C. reinhardtii [4,5,6]
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