Effects of different cultivation conditions on the production of β-cyclocitral and β-ionone in Microcystis aeruginosa

Background: Cyanobacteria blooms have become a major environmental problem and concern because of secondary metabolites produced by cyanobacteria released into the water. Cyanobacteria produce volatile organic compounds (VOCs), such as the compounds beta-cyclocitral and beta-ionone, which comprise odors, off-flavors, defense compounds, as well as growth regulators. Therefore, the general objective of this work was to evaluate the VOCs produced by two strains of Microcystis aeruginosa, differing in their ability to produce microcystins (LTPNA 01-non-producing and LTPNA 08-toxin-producing). The analysis of VOC production was carried out in (1) normal culture conditions, (2) under different light intensities (LI), and (3) after the external application of beta-ionone in both cultures. Results: The results showed that beta-cyclocitral and beta-ionone are produced in all growth phases of LTPNA 01 and LTPNA 08. Both strains were producers of beta-cyclocitral and beta-ionone in normal culture conditions. It was observed that the beta-cyclocitral concentration was higher than beta-ionone in all light intensities investigated in this study. Additionally, the strain LTPNA 01 produced more beta-cyclocitral than LTPNA 08 at almost all times and Lls analyzed. However, the strain LTPNA 08 produced more beta-ionone, mainly at the initial times. In addition, the experiment results with the external addition of beta-ionone in the cultures showed that the strain LTPNA 01 produced more beta-cyclocitral in control conditions than in treatment. Nonetheless, beta-ionone production was higher in treatment conditions in LTPNA 08, indicating that the addition of beta-ionone may favor the production of these compounds and inhibit the production of beta-cyclocitral. Conclusion: Our results showed that some abiotic factors, such as different light intensities and external application of beta-ionone, can be triggers that lead to the production of VOCs.