title: Decolourisation of Acid Orange 7 recalcitrant auto-oxidation coloured by-products using an acclimatised mixed bacterial culture.
abstract: This study focuses on the biodegradation of recalcitrant, coloured compounds resulting from auto-oxidation of Acid Orange 7 (AO7) in a sequential facultative anaerobic-aerobic treatment system. A novel mixed bacterial culture, BAC-ZS, consisting of Brevibacillus panacihumi strain ZB1, Lysinibacillus fusiformis strain ZB2, and Enterococcus faecalis strain ZL bacteria were isolated from environmental samples. The acclimatisation of the mixed culture was carried out in an AO7 decolourised solution. The acclimatised mixed culture showed 98 % decolourisation within 2 h of facultative anaerobic treatment using yeast extract and glucose as co-substrate. Subsequent aerobic post treatment caused auto-oxidation reaction forming dark coloured compounds that reduced the percentage decolourisation to 73 %. Interestingly, further agitations of the mixed culture in the solution over a period of 48 h significantly decolourise the coloured compounds and increased the decolourisation percentage to 90 %. Analyses of the degradation compounds using UV-visible spectrophotometer, Fourier transform infrared spectroscopy (FTIR) and high performance liquid chromatography (HPLC) showed complete degradation of recalcitrant AO7 by the novel BAC-ZS. Phytotoxicity tests using Cucumis sativus confirmed the dye solution after post aerobic treatment were less toxic compared to the parent dye. The quantitative real-time PCR revealed that E. faecalis strain ZL was the dominant strain in the acclimatised mix culture.
authors.affiliation: Department of Biosciences and Health Sciences, Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310, Skudai, Johor, Malaysia.
authors.forename: Hui Han
authors.initials: HH
authors.lastname: Bay
authors.forename: Chi Kim
authors.initials: CK
authors.lastname: Lim
authors.forename: Thuan Chien
authors.initials: TC
authors.lastname: Kee
authors.forename: Ismail
authors.initials: I
authors.lastname: Ware
authors.forename: Giek Far
authors.initials: GF
authors.lastname: Chan
authors.forename: Shafinaz
authors.initials: S
authors.lastname: Shahir
authors.forename: Zaharah
authors.initials: Z
authors.lastname: Ibrahim
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001391:Azo Compounds / Q000378:metabolism* / Q000633:toxicity; D056449:Bacillales / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001557:Benzenesulfonates / Q000378:metabolism* / Q000633:toxicity; D001673:Biodegradation, Environmental; D004396:Coloring Agents / Q000378:metabolism* / Q000633:toxicity; D018553:Cucumis sativus / Q000187:drug effects / Q000254:growth & development; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D013293:Enterococcus faecalis / Q000235:genetics / Q000378:metabolism*; D018525:Germination / Q000187:drug effects; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D060888:Real-Time Polymerase Chain Reaction; D012639:Seeds / Q000187:drug effects; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001391:Azo Compounds; D001557:Benzenesulfonates; D004396:Coloring Agents; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; C014722:2-naphthol orange