Next, we tested various common mediators in laccase-mediated reactions for degrading ATR, namely 1-hydroxybenzotriazole (HBT), 2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPO), guaiacol (GA), and syringaldehyde (SA). Mediators are a class of compounds that can be oxidized by laccase into intermediates early in the reaction, which then react with the nonphenolic groups of the substrates. Of the four mediators examined, the HBT group in the BNNS-Arg@Lac system achieved the highest ATR removal (~96%), followed by GA (~52%), SA (~10%), and TEMPO (~5%). nLaccase showed the same order for ATR removal efficiency (HBT>GA>SA>TEMPO). However, even with the addition of mediators, nlaccase mostly showed a lower reduction in ATR concentration. By adding only HBT, ATR and HBT can also conjugate together, decreasing the ATR concentration (Figure ). Although mediators like HBT can improve ATR degradation (for example for BNNS-Arg@Lac, with HBT, an ~96% degradation rate was achieved versus ~69% without it), the addition of HBT caused toxicity to chlorophyll a synthesis in the model organism, C. vulgaris (Figure ). ATR, HBT, and their mixture all showed inhibition to chlorophyll a synthesis compared with the control group in normal algal growth. Conversely, chlorophyll a synthesis was not significantly impacted when treated with BNNS-Arg@Lac and natural laccase in the presence of HBT, suggesting that they can alleviate the inhibitory effects of HBT. Nonetheless, mediators can complicate the degradation system and pose potential environmental concerns for practical applications.