Microalgal secondary metabolites: effect of climatic variables, seasons, and photocycles on the biogeneration of volatile organic compounds (VOCs)

Abstract

Microalgae produce many metabolites with diversified structures that play important roles in their development. This work evaluated the effects of different climatic variables, seasons, and light/dark phases in the production of volatile organic compounds by Scenedesmus obliquus CPCC05, focusing on the simulation of climatic variables (average temperature, maximum light intensity, and light hours per day) of the extreme geographical positions of Brazil based on tropical Am, tropical Aw, and subtropical Cfa climates found in Joao Pessoa-PB, Rio Branco-AC, Boa Vista-RR, and Rio Grande-RS, in summer and winter seasons. For the best condition in this first step, the light/dark phases together with the residence time of the culture were evaluated. A total of 45 compounds were identified in all conditions studied. The main volatile groups found were hydrocarbons, aldehydes, ketones, alcohols, and terpenes identified in both geographic locations. Among these, hydrocarbons were the main biomarkers of the subtropical Cfa climate, while the ketone group was produced mainly in warmer climates, such as the Aw tropical climate. In the experiments of light/dark phases, a total of 34 compounds were identified. 2-Pentenol and decanal were only produced in the light phase, while 1-pentanol and 2-ethyl hexanol were only found in the dark phase. The main volatile compound found was 3-methylbutanol reaching a total area abundance of 14.10%. The major compounds detected during the cultures were originated and derived from the terpenoid pathways, fatty acids, and amino acid derivates.