Photoproduction of Acetaldehyde from Bacteria-Derived Dissolved Organic Matter

We explored the photoproduction of oxygenated volatile organic compounds (OVOCs) from marine bacteria-derived dissolved organic matter (B-DOM). B-DOM was obtained from the growth phase to the stationary phase in a culture experiment with marine bacteria in coastal seawater. B-DOM composition was evaluated through chromophoric dissolved organic matter (CDOM) and fluorescent dissolved organic matter (FDOM) (e.g., amino acid-like, humic-like). Photoproduced OVOCs from B-DOM were measured using Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-ToF-MS). Acetaldehyde was photoproduced from B-DOM in proportion to light exposure time, with photoproduction rates of 0.20-0.51 nM h^-1. However, no direct quantitative relationship between the acetaldehyde photoproduction rates and the levels of CDOM or FDOM was observed. Since acetaldehyde photoproduction was highest during the growth phase of the bacterial culture, it was suggested that the fraction of B-DOM susceptible to microbial degradation contributes to the source of acetaldehyde. In contrast, the photoproduction of acetone from B-DOM was minimal, implying sources other than B-DOM are responsible for acetone on the marine surface. These findings suggest that B-DOM has the potential to generate acetaldehyde upon solar exposure, with implications for understanding the contribution of microbial-derived organic matter to the production of these compounds in the marine environment.