TEXTILE DYE DEGRADATION USING HALOPHILIC OXIDASES

Abstract

Mostly synthetic dyes are used by the textile industry, which uses 10,000 different dyes to print and colour different kinds of fabrics and controls 75% of the global market for azo dyes. In current study, halophilic bacterium Lentibacillus salarius BPIITR was found to produce extracellular oxidase enzyme in submerged fermentation. The bacterial growth reached maximum optical density of 10.2 ± 0.45 at 42 hours of incubation. Among different substrates studied for their affinities, 9.85 ± 0.35, 7.07 ± 0.12, 1.92 ± 0.11, 28.90 ± 0.48 IU/mL activities were achieved with 4-methoxybenzaldehyde, 4-methoxybenzyl alcohol, 4-hydroxybenzyl alcohol, guaiacol and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid, respectively. At different ABTS concentrations, the relative increase of 36.47 % was observed at 0.4 mM, whereas it further increased to 72.65 % at 0.6 mM. The highest enzyme activity was observed at 5 minutes of incubation, however 85.48 %, 58.81 % and 33.71 % relative activity was observed at 2, 10, 15 minutes of incubation. At 50 °C, enzyme activity reached a maximum of 37 ± 0.18 IU/mL and it further declined to 28±0.22 IU/mL at 55°C. Furthermore, The residual activity declined drastically after 90 minutes at 50 °C to 70.89%, whereas the residual activity remained significantly high at lower studied temperatures. In addition, change in the buffer composition at same pH affected the enzyme activity. For instance, at pH 8, with sodium phosphate buffer and sodium glycine buffer 29.33 and 8.88 IU/mL of activity was observed, respectively. Different dyes mainly methyl orange (MOλ464), Reactive Black 5 (RB5λ665), Coomassie brilliant blue R-250 (CBBRλ549), Coomassie brilliant blue G-250 (CBBGλ577), Bromophenol Blue (BPBλ665), Acid Blue 147 (AB147λ615), Congo Red (CRλ497), were degraded using halophilic oxidase under the optimum reaction conditions. Among these dyes methyl orange found to degrade up to 67.73% at 6 hours of incubation. In addition, it was found that enzyme can degrade methyl orange up to 89.14 % in 10 hours. Further acetone precipitated enzymes were crosslinked with glutaraldehyde. Cross-linked enzymes aggregates exhibited specific activity of 31.19 IU/mg at 0.1mM glutaraldehyde concentration.