Chlorophyll Oxidative Metabolism During the Phototrophic and Heterotrophic Growth of Scenedesmus obliquus

Abstract

Different cultivation strategies have been developed with the aim of increasing the production rate of microalgal pigments. Specifically, biotechnological approaches are designed to increase antioxidant metabolites as chlorophyll and carotenoids. However, although significant advances have been built up, available information regarding both the chlorophyll metabolism and their oxidative reactions in photobioreactors is scarce. To unravel such processes, the detailed chlorophyll and carotenoid fraction of Scenedesmus obliquus has been studied by HPLC-ESI/APCI-hrTOF-MS from phototrophic and heterotrophic cultures. Scenedesmus is provided with a controlled strategy of interconversion between chlorophyll a and b to avoid the formation of reactive oxygen species (ROS) at high irradiances in addition to the photoacclimation of carotenoids. Indeed, precise kinetics of 132-hydroxy- and 151-hydroxy-lactone chlorophyll metabolites shows the existence of a chlorophyll oxidative metabolism as a tool to manage the excess of energy at high light conditions. Unexpectedly, the oxidation under phototrophy favored chlorophyll b metabolites over the chlorophyll a series, while the heterotrophic conditions exclusively induced the formation of 132-hydroxy-chlorophyll a. In parallel, during the first 48 h of growth in the dark, the chlorophyll fraction maintained a promising steady state. Although future studies are required to resolve the biochemical reactions implied in the chlorophyll oxidative metabolism, the present results agree with phytoplankton metabolism.

Antioxidants: Classification, Natural Sources, Activity/Capacity Measurements, and Usefulness for the Synthesis of Nanoparticles

“…However, efficient extraction and purification are required for the recovery of phycobiliproteins on an industrial scale [ 249 ]. In 2019, the Special Issue of Antioxidants focused on recent investigations concerning marine algal antioxidants and specific antioxidant networks functioning in algae [ 248 , 249 , 250 , 251 , 252 , 253 , 254 , 255 , 256 , 257 , 258 , 259 ].…”

Coffee (Coffea arabica L.) by-Products as a Source of Carotenoids and Phenolic Compounds—Evaluation of Varieties With Different Peel Color

“…Identification of carotenoids was performed by comparing their UV/Vis and APcI(+)-MS1 spectra with data published previously (Britton, 1995;de Rosso and Mercadante, 2007;Maroneze et al, 2019).…”

“…de Castro and Marraccini, 2006). These primary photosynthetic pigments were identified in our work by their protonated molecules [M+H] + at m/z 892 and 906, respectively, and their corresponding absorption maxima, according to Maroneze et al (2019). Table 5 compiles the criteria for identification of the remaining carotenoids and the corresponding references.…”

Marine Algal Antioxidants

“…Together with carotenoids, chlorophylls and their derivatives are also of interest for biotechnological applications [13]. Enhancing the production of chlorophylls per biomass unit in microalgae and understanding the biosynthetic and degradation pathways of such molecules is therefore biotechnologically relevant.…”

“…Enhancing the production of chlorophylls per biomass unit in microalgae and understanding the biosynthetic and degradation pathways of such molecules is therefore biotechnologically relevant. The study by Maroneze and collaborators [13] reported and discussed the modulation of the chlorophyll and carotenoid contents in the model species Scenedesmus obliquus with respect to the growth phase and the presence/absence of light, turning growth from autotrophy to heterotrophy. The authors demonstrated that the content and chemical forms of these compounds are affected by growth conditions, laying the foundation for up-scaling and massive production for industrial application.…”