Efficiency of Imazapic Degradation: an Assessment of LacMeta Treatments Utilizing Whole Cell

The extensive use of herbicides such as imazapic, from the imidazolinone class, raises environmental concerns due to its persistence and toxicity in ecosystems and subsequent crops. Enzymatic bioremediation emerges as a sustainable alternative for the mitigation of these contaminants. This study investigated the potential of the metagenomic laccase, LacMeta, expressed in Escherichia coli BL21 (DE3), to degrade imazapic using a whole-cell approach. LacMeta expression was optimized with CuSO₄, which proved to be four times more effective than IPTG. The E. coli + LacMeta cells demonstrated high tolerance to the herbicide, maintaining cell viability even at high doses (350 g/ha). Notably, the enzymatic activity of LacMeta was not inhibited by imazapic; on the contrary, it was stimulated, reaching a specific activity nearly three times higher in the presence of the herbicide compared to the control. Degradation was confirmed by UV-Visible spectroscopy, which showed the disappearance of imazapic’s characteristic peaks (200–280 nm) over 15 days. ¹H-NMR and FTIR analyses corroborated the degradation, indicating structural changes in the herbicide molecule, particularly in the aromatic ring region (signals at 8.25 and 8.50 ppm). Phytotoxicity assays with lettuce seeds (Lactuca sativa) confirmed that treatment with the LacMeta-containing supernatant cell free significantly reduced the toxicity of imazapic in the soil. The results demonstrate that LacMeta has high potential for the bioremediation of imazapic, and the whole-cell approach represents a promising and cost-effective strategy for the decontamination of environments impacted by this herbicide.