Photosensitization optimization in Chlorella: Driving the acclimation-enhanced degradation of sulfonamide antibiotics

The proliferation of sulfonamide antibiotics (SAs) in aquatic ecosystems poses a severe threat to environmental integrity and human well-being. This research employs an acclimation strategy using Chlorella pyrenoidosas to enhance the photo-sensitized degradation efficacy of sulfamethoxazole (SMX) and sulfisoxazole (SIZ). The acclimated Chlorella exhibits remarkable degradation capabilities, with improvements of approximately 9.7 times for SMX and 4.2 times for SIZ, respectively, compared to non-acclimated strains. These improvements are linked to increased growth rates, higher chlorophyll levels, enhanced extracellular organic matter (EOM) production, and elevated antioxidant enzyme activities. The enhanced performance is attributed to refined enzymatic and metabolic processes promoting photosynthesis, energy conversion, and the degradation of SAs. Through response surface methodology, this approach is refined to achieve optimal water remediation results, attaining a degradation rate of 78.04 %. The EOM content increases by up to 68.33 %, while growth rates improve by 1.06 to 1.14 times, indicating superior tolerance. A biphasic response to antibiotic concentrations is also observed, where low concentrations facilitate degradation while high concentrations have an inhibitory effect. This characteristic is reflected by significant increases in antioxidant enzyme activities, particularly in the case of glutathione reductase (GR) and catalase (CAT) at concentrations below 1 mg/L.