Biodegradation of 3-chlorobenzoate and 3-hydroxybenzoate by polyurethane foam immobilized cells of Bacillus sp. OS13

Due to widespread use, persistence and toxicity, 3-chlorobenzoate (3-CBA) is well-known as an environmental pollutant. Bacillus sp. OS13, isolated as a 2-nitrotoluene tolerant, has the ability to utilize 3-CBA (4 mM) as a sole source of carbon and energy. Nevertheless, this organism has also simultaneously utilized the 4-chlorophthalate, 3-hydroxybenzoate, protocatechuate and 2-chlorobenzoate as a growth substrate. In order to achieve our study objective, firstly we followed the response surface methodology (RSM), and assessed the optimal growth conditions of pH (7.20) and temperature (33 degrees C) for Bacillus sp. OS13 to degrade the 3-CBA. We also determined the two major degradation products (i.e., 3-hydoxybenzoate and protocatechuate) of 3-CBA by using HPLC and GC-MS. Additionally, the activities of 3-hydroxybenzoate-4-hydroxylase and protocatechuate 3,4-dioxygenase enzymes in the cell-free extract were also observed. Thus, in Bacillus sp. OS13, 3-CBA was transformed into protocatechuate via 3-hydroxybenzoate with the release of chloride ions and thereby enter into the ortho-cleavage pathway. In addition, there was complete degradation of 3-CBA (4 mM) and 3-hydroxybenzoate (4 mM) by the polyurethane foam (PUF)-immobilized cells of Bacillus sp. within 60 h. Furthermore, when the initial concentrations of both substrates were increased to 10 mM, the same PUF-immobilized cells were degraded approximately 98% of both substrates within 60 h. Our findings would be very useful towards the environmental management of 3-CBA in the surrounding contaminated environment. (C) 2016 Elsevier Ltd. All rights reserved.