Enzyme and biosurfactant production as strategy for bis(2-ethylhexyl) phthalate degradation by Fusarium culmorum: Metabolic pathway proposal using quantum chemical investigation.

Bis(2-ethylhexyl) phthalate is a globally used plastic additive that can exhibit toxic effects on environmental and human health. In this study, Fusarium culmorum was grown on BEHP (3000 mg/L), used as a sole carbon source, in liquid fermentation. A glucose medium was used as a control. Growth kinetics, protein content, and esterase activity were determined. BEHP biodegradation compounds were detected through GC-MS, and a metabolic pathway was proposed using quantum chemical modeling to predict the stability of the generated products. F. culmorum had a μ value 1.6-fold more in the control medium (0.032 h-1) than in the BEHP-supplemented medium (0.02 h-1). The maximum volumetric esterase activity was 63-fold more in the BEHP-supplemented cultures (6007.5 U/L) than that in the control cultures (95.7 U/L). Five (28.4, 34.5, 47.9, 84, and 178.2 kDa approx.) and two (33 and 49.5 kDa approx.) esterase isoenzymes were detected in BEHP-supplemented and in the control cultures, respectively, indicating that the BEHP supplementation significantly induced esterase production. The GC-MS revealed that F. culmorum degraded BEHP and synthesized compounds, including oleic acid, lauric acid, palmitic acid, and palmitoleic acid, that can be converted into natural surfactants, which make the substrate bioavailable (through micelles formation) for uptake and metabolism. To the best of our knowledge, this is the first study suggesting a microorganism-mediated degradation of a plasticizer (i.e. phthalate ester) associated with a concomitant natural surfactant production.