Single and combined exposure to MC-LR and BMAA confirm suitability of Aegagropila linnaei for use in green liver systems(®)-A case study with cyanobacterial toxins.

The filamentous green algae Aegagropila linnaei was tested for its uptake capacity of the cyanobacterial toxins microcystin-LR (MC-LR) and β-N-methylamino-l-alanine (BMAA) in order to approve the suitability of its use in the Green Liver System(®). Uptake into the algae and toxin reduction in the medium were analyzed by LC-MS/MS after static exposure for one week to 20μgL(-1) MC-LR, 80μgL(-1) BMAA, and 20μgL(-1) MC-LR together with 80μgL(-1) BMAA, respectively. BMAA was effectively removed by A. linnaei within 5 days compared to only around 35% removal of the initial exposure concentration in the case of MC-LR, independent of the application mode, in single or in a mixture. However, differences were found for BMAA amounts taken up into the tissue in that it was higher if applied in combination with MC-LR. Additionally, physiological responses such as the activity of biotransformation enzyme glutathione S-transferase (GST), antioxidant enzymes peroxidase (POD) and catalase (CAT) as well as the development of the reactive oxygen species hydrogen peroxide (H2O2) were compared between the different treatment groups in order to determine possible harmful effects of the toxin exposure on the algae. In contrast to the toxin exposure to a single toxin with no significant enzymatic response, exposure to the toxin mixture provoked an immediate increase in GST and CAT activity after one day as well as after longer exposure for one week, hinting on an enhanced need for prevention against exposure derived reactive oxygen species as well as putative biotransformation attempts in a mixture exposure scenario.