Concerted action of extracellular and cytoplasmic esterase and urethane-cleaving activities during Impranil biodegradation by Alicycliphilus denitrificans BQ1.

Abstract

The concerted action of commercial esterases, proteases and amidases has been demonstrated to be relevant in polyurethane (PU) degradation by in vitro experiments. However, the spatial and temporal dynamics of these activities during PU biodegradation by PU-degrading bacteria have not been addressed. Here, we examined the capability of Alicycliphilus denitrificans BQ1 to biodegrade the polyester (PS)-PU Impranil, analyzed the temporal and spatial coordination between the extracellular and cytoplasmic esterase and urethane-cleaving activities, and their independent and combined effects on Impranil biodegradation. A. denitrificans BQ1 grew in Impranil, and its clearing was correlated with the cleavage of ester and urethane groups since early times, with decrements of some Impranil compounds and the appearance of biodegradation products. While extracellular esterase was active at early times with its maximum at 18h, urethanase appeared at this time and increased up to the end of the analysis (48h), with the cytoplasmic activities behaving similarly but with lower levels than the extracellular ones. Both enzymatic activities exhibited distinct substrate specificity depending on their cellular localization and cultivation times, suggesting they cleave differentially located groups. As the urethane cleavage occurred since early times, when no urethane-cleaving activity was detected, different proteins should be acting at early and late times. In vitro experiments with independent or combined cellular protein fractions supported the previous deduction and confirmed the concerted action of extracellular and cytoplasmic esterase and urethane-cleaving activities. A two-stage process for Impranil degradation by A. denitrificans BQ1 is proposed.