Biodegradation of 17α-Ethinylestradiol in Sediment/Water Systems Affected by Two Different Rhamnolipidic Homologues

The shake flask aerobic biodegradation experiment was used to study the effect on biodegradation of 17α-ethinylestradiol (EE2) in the sediment/water system affected by mono-rhamnolipid (RL-F1) and di-rhamnolipid (RL-F2). The results showed that RL-F1 and RL-F2 had no inhibitory effect on EE2 biodegradation. The effect of RL-F1 on enhanced biodegradation of EE2 was larger than that of RL-F2. In 6 mM and 10 mM of the rhamnolipidic functioned systems, EE2 biotransformation rates affected by RL-F1 were respectively 7.6 and 8.2 times of those of RL-F2 corresponding systems. The accumulation and change rule of the intermediate metabolites M.1 with the polarity greater than EE2 and M.3 with the polarity weaker then EE2 in the biodegradation process were analyzed. In the RL-F2 systems, the time for the accumulative amounts of M.1 and M.3 up to the peak was correspondingly lagged and their output was relatively lower. The testing result of rhamnolipids in the sample showed that RL-F1 was more biodegradable than RL-F2. The bioavailability of di-rhamnolipidic micelle solubilized with EE2 was inferior to that of mono-rhamnolipid, making the organic uptake and metabolism process of microorganisms slow down.