Biocompounds from an endosymbiotic dinoflagellate: genesis, composition, biological activities and sustainability

Abstract

Modern baselines that make up the paradigm of sustainable development of aquaculture highlight microalgae as promising organisms for the suitable fish production growth. Microalgae biomass offers opportunities of processes and products not only for aquaculture sector, but also for human nutrition, wastewater treatment, bioenergy, biosensors, and new drugs development. For this latter application, marine dinoflagellates have emerged considerably in recent years due to the chemodiversity of secondary metabolites produced by them. However, a number of challenges are related to dinoflagellate cultivation, for example: sensitivity to shear stresses, nutritional complexity, sensitivity to thermal fluctuations, non-growth under sub-optimal conditions, etc. In view of this, the present thesis was built aimed at contributing to the improvement of marine dinoflagellates cultivation, in particular, for the endosymbiotic dinoflagellate Durusdinium glynnii. This thesis is organized into two main sections, the first one consisting of three review articles, and the second organized over three of research articles. In the first article, global dinoflagellate research output was analyzed based on a scientometric approach using the Scopus database published between 1970 and 2020. The historical data proven that dinoflagellate research is an active research area, highlighting the themes of "harmful algal blooms" and "symbiosis with coral reefs". In analyzing data from the last decade of research, it was possible to identify a potential interest in cultivation and biotechnology of dinoflagellate. In the second article, some of the main genera of dinoflagellates (i.e., Alexandrium, Amphidinium, Gymnodinium, Karlodinium, and dinoflagellates of the family Symbiodiniaceae) with potential for cultivation were presented and reviewed. This article applications of dinoflagellates in aquaculture were also pointed out. Finally, in the third article, the potential of microalgae to achieve the important Sustainable Development Goals proposed by the United Nations was reviewed. In this article, the main challenges and the sustainable techniques used in the upstream and downstream processing of the microalgae production chain were presented. In the fourth article an investigation of the effects of irradiance on growth and biochemical composition of D. glynnii was conducted. Under optimal growth conditions, D. glynnii accumulated high levels of docosahexaenoic acid (DHA), while the accumulation of the carotenoid peridinin occurred when exposed to high irradiance – proving a photoprotective role of this carotenoid. Additionally, extracts of D. glynnii biomass showed potential scavenging free radicals by means of antioxidant activity assays. In the fifth article, nutritional strategies, based on nitrogen source and concentration, were evaluated as a way to alleviate thermal and light stress – two important parameters for productive scale-up of dinoflagellates. For light stress, the use of sodium nitrate as a nitrogen source was more suitable, while for thermal stress, only urea in high concentrations was able to allow D. glynnii cell division. Furthermore, some ecological implications of the findings of this study were demonstrated towards contribute to the knowledge of the phenomena related with the resistance of certain coral reefs to temperature rise. Finally, in the last article, a holistic approach for the production of antibacterial compounds using wastewater from shrimp production was proven. D. glynnii showed better growth performance using aquaculture wastewater than using a traditional culture medium, and the biomass produced in the wastewater was able to inhibit two Vibrio strains. These findings contribute to the development of circularity in aquaculture. In conclusion, dinoflagellate research is associated with several important issues for society in terms of social, economic, and public health issues. Recent advances in cultivation and biotechnology of dinoflagellates can help to understand the occurrence of harmful blooms in natural environments, as well as in the development of new sustainable products and processes.