Degradation of Multiple Peptides by Microcystin-Degrader Paucibacter toxinivorans (2C20)

Since conventional drinking water treatments applied in different countries are inefficient at eliminating potentially toxic cyanobacterial peptides, a number of bacteria have been studied as an alternative to biological filters for the removal of microcystins (MCs). Here, we evaluated the degradation of not only MCs variants (-LR/DM-LR/-RR/-LF/-YR), but also non-MCs peptides (anabaenopeptins A/B, aerucyclamides A/D) by Paucibactertoxinivorans over 7 days. We also evaluated the degradation rate of MC-LR in a peptide mix, with all peptides tested, and in the presence of M. aeruginosa crude extract. Furthermore, biodegradation was assessed for non-cyanobacterial peptides with different chemical structures, such as cyclosporin A, (Glu1)-fibrinopeptide-B, leucine-enkephalin, and oxytocin. When cyanopeptides were individually added, P. toxinivorans degraded them (99%) over 7 days, except for MC-LR and -RR, which decreased by about 85 and 90%, respectively. The degradation rate of MC-LR decreased in the peptide mix compared to an individual compound, however, in the presence of the Microcystis extract, it was degraded considerably faster (3 days). It was noted that biodegradation rates decreased in the mix for all MCs while non-MCs peptides were immediately degraded. UPLC–QTOF–MS/MS allowed us to identify two linear biodegradation products for MC-LR and MC-YR, and one for MC-LF. Furthermore, P. toxinivorans demonstrated complete degradation of non-cyanobacterial peptides, with the exception of oxytocin, where around 50% remained after 7 days. Thus, although P. toxinivorans was previously identified as a MC-degrader, it also degrades a wide range of peptides under a range of conditions, which could be optimized as a potential biological tool for water treatment

A paradigm-shift in water treatment: In-reservoir UV-LED-driven TiO2 photocatalysis for the removal of cyanobacteria – a mesocosm study

Potentially harmful cyanobacteria challenge potable water treatment with high biomass events and dissolved toxic and nuisance metabolites globally. Retrofitting existing water treatment infrastructure is often impractical, if not impossible, and often prohibitively expensive. In a paradigm-shifting move we propose in-reservoir pre-treatment of cyanobacteria-contaminated raw waters to ease the burden on existing water treatment infrastructure. In an iterative design approach over three years, treatment modules have been designed, refined, and optimised in bench and pilot-scale studies for in-reservoir deployment. TiO2-coated beads made from recycled glass are employed in conjunction with UV-light emitting diodes (LEDs) to create highly reactive hydroxyl radicals that preferably remove cyanobacteria and subsequently released cyanotoxins from raw water. In a mesocosm study in a drinking water reservoir in Brazil water quality parameters were markedly improved within 72h of deployment and cyanobacterial presence was decreased by over 90% without affecting other phytoplankton communities. The treatment system is virtually plastic-free, low cost, utilises recycled materials and could ultimately be powered by renewable energies, thus providing a true green treatment option. We have conclusively demonstrated that a paradigm-shift towards in-reservoir treatment is not only possible but feasible and can provide a valuable addition to conventional water treatment methods