**1. Introduction**

Acetaminophen (N-acetyl-*p*-aminophenol; ACE) is a widely used representative medicine. As a nonsteroidal anti-inflammatory drugs (NSAIDs), ACE exhibits analgesic and antipyretic properties and acts via inhibition of cyclooxygenase enzymes [1]. The reported concentrations of ACE range from 0.003 to 30 mg L−<sup>1</sup> in stream water, sewage treatment plant influents and e ffluents [2–4]. The frequent detection of ACE in aquatic environments has raised concerns regarding its potential deleterious e ffects on the environments [5–8].

Mangrove ecosystems along the coastlines of tropical and subtropical regions are important intertidal estuary wetlands that considered to be significant sinks of pollutants from contaminated tidal water and discharges from freshwater [9]. The mangroves of Guandu and Bali are located on the banks of the Danshui River, one of the most polluted rivers in northern Taiwan. The concentrations and degradation of nonylphenol, sulfonamides and polycyclic aromatic hydrocarbons in the mangrove sediments have been reported [10–13].

Physicochemical methods such as primarily advanced oxidation processes (AOPs), homogeneous and heterogeneous photocatalysis, Fenton and Fenton like reactions, ozonation, and methods involving ultrasound and microwave treatments, or electrochemical processes are not appropriate for treating ACE in mangrove sediments [14]. Biodegradation is an effective strategy to remove organic pollutants from sediments. Most studies on pharmaceutical biodegradation are focused on their removal during wastewater treatment processes [15]. Some investigations evaluated the microbial degradation of drugs and artificial compounds in freshwater [16] as well as in ocean and estuary waters [17]. The microbial degradation of drugs depends on the prevailing oxygen availability and redox conditions in sediments. However, little is known regarding the aerobic and anaerobic biodegradation potential of ACE in mangrove sediments.

Biodegradation is believed to be an effective strategy for eliminating contaminating ACE in environments. To enhance the efficiency of degradation, three remedial strategies have been proposed: natural attenuation, bioaugmentation and biostimulation [18]. Microbial degradation of ACE has been observed in bacterial strains. *Pseudomonas aeruginosa* strain HJ1012 was isolated on ACE as a sole carbon [19]. *Pseudomonas moorei* KB4 can metabolize ACE, with *p*-aminophenol and hydroquinone identified as degradation products [14]. Two ACE-metabolizing strains, *Delftia tsuruhatensis* and *Pseudomonas aeruginosa*, were isolated from the membrane bioreactor [20]. White rot fungus *Pleurotus eryngii* is one of the most widespread mushrooms consumed in the world. spent mushroom compost (SMC) is a mushroom industry waste which contains extracellular enzymes with organic pollutant degradation ability [21]. The addition of enzyme containing microcapsules (MC) was found to be effective for aerobic degradation of organic pollutants [12] and the aerobic degradation of tetracyclines in the river sediments [22]. Addition of NaHCO3, Na2SO4, andNaNO3 could create methanogenic conditions, sulfate-reducing conditions and nitrate-reducing conditions, respectively, as well as enhance anaerobic degradation of organic pollutants [13]. Therefore, the addition of ACE-degrading bacteria, MC and electron acceptors such as NaNO3, Na2SO4 and NaHCO3 were used to promote ACE degradation in this study.

The aim of this study is to evaluate strategies for enhancing biodegradation of ACE in mangrove sediments under aerobic and anaerobic conditions. Three strategies, including addition of MC, addition of ACE-degrading bacterial strains isolated from sediments and addition of electron acceptors (NaNO3, Na2SO4 or NaHCO3). The microbial communities involved in aerobic and anaerobic degradation of ACE in the mangrove sediments were investigated.

#### **2. Materials and Methods**
