Impact of biogenic substrates on sulfamethoxazole biodegradation kinetics by Achromobacter denitrificans strain PR1

Abstract

Pure cultures have been found to degrade pharmaceutical compounds. However, these cultures are rarely characterized kinetically at environmentally relevant concentrations. This study investigated the kinetics of sulfamethoxazole (SMX) degradation by Achromobacter denitrificans strain PR1 at a wide range of concentrations, from ng/L to mg/L, to assess the feasibility of using it for bioaugmentation purposes. Complete removal of SMX occurred for all concentrations tested, i.e., 150 mg/L, 500 µg/L, 20 µg/L, and 600 ng/L. The reaction rate coefficients (k) for the strain at the ng/L SMX range were: 63.4 ± 8.6, 570.1 ± 15.1 and 414.9 ± 124.2 L/g[Formula: see text]·day), for tests fed without a supplemental carbon source, with acetate, and with succinate, respectively. These results were significantly higher than the value reported for non-augmented activated sludge (0.41 L/(g [Formula: see text]·day) with hundreds of ng/L of SMX. The simultaneous consumption of an additional carbon source and SMX suggested that the energetic efficiency of the cells, boosted by the presence of biogenic substrates, was important in increasing the SMX degradation rate. The accumulation of 3-amino-5-methylisoxazole was observed as the only metabolite, which was found to be non-toxic. SMX inhibited the Vibrio fischeri luminescence after 5 min of contact, with EC values of about 53 mg/L. However, this study suggested that the strain PR1 still can degrade SMX up to 150 mg/L. The results of this work demonstrated that SMX degradation kinetics by A. denitrificans PR1 compares favorably with activated sludge and the strain is a potentially interesting organism for bioaugmentation for SMX removal from polluted waters.

Selecting Bacteria Candidates for the Bioaugmentation of Activated Sludge to Improve the Aerobic Treatment of Landfill Leachate

“…The successful colonization of a bioreactor by inoculated bacteria is challenging as they are likely to encounter the following obstacles within the biological unit, i.e., environmental pressure due to protozoan grazing and/or competition with indigenous microorganisms as well as fluctuations of the abiotic factors such as temperature, pH, salinity, the hydrodynamic conditions, organic loading rate, and the availability of nutrients and oxygen, which causes them to die or to wash out of the system along with the effluent [23][24][25][26]. A versatile degradation capacity towards a variety of compounds is often reported as being a pivotal competence of potential candidates for bioaugmentation [27,28]. However, adding bacteria with the desirable catabolic capabilities into the AS does not always guarantee an enhanced biodegradation of the compounds in wastewater [29,30].…”

Bioaugmentation of activated sludge with Achromobacter denitrificans PR1 for enhancing the biotransformation of sulfamethoxazole and its human conjugates in real wastewater: Kinetic tests and modelling

“…We previously showed that the presence of a biogenic substrate, e.g. acetate or succinate, provided for an 8-fold increase of SMX biotransformation kinetics by PR1 [14]. In the current study, the initial concentration of acetate was approximately 137 to 152 mg COD L -1 , supplemented with preclarified wastewater to (i) the bioaugmented reactor (A4) (Fig.…”

“…Pure culture biotransformation tests had previously shown that the A.denitrificans PR1 is capable of biotransformation of SMX under both aerobic [14] and anoxic conditions (data not shown). Hence the extent of SMX removal under anoxic conditions was also assessed and compared to those obtained in aerobic conditions.…”

“…2d). By using the obtained parameters k bio,AS , q bio_AS from the A1 test, k bio,PR1 (56.20 ± 3.70 L gTSS d -1 ) from our previous study [14], fitting of measured data in the substrate depletion phase using cometabolic model as described in Table 2 resulted in estimation of q bio,PR1 = 528.39 ± 6.78 L gTSS -1 d -1 . This q bio,PR1 value is consistent with rate constants (k bio,PR1 = 445.6 -570.1 L gTSS -1 d -1 ) previously obtained with PR1 when acetate was supplemented as a biogenic substrate to enhance the biotranforamtion rate of SMX in pure culture biodegradation tests [14].…”

“…Previously, we showed that a pure culture of Achromobacter denitrificans PR1 could exhibit faster biotransformation kinetics (up to two to three orders of magnitude higher) of SMX compared to AS alone [14], even at the low SMX concentrations typical of wastewater effluents. Given its ability to degrade SMX in the presence and/or absence of other additional carbon sources (acetate and succinate) at environmentally relevant concentrations (typical of e.g., wastewater effluents), the strain likely has potential for treating SMX in wastewater upon bioaugmentation.…”