The microbial decolourisation of textile dyes

Kennerley, V.M., 2000. The microbial decolourisation of textile dyes. PhD, Nottingham Trent University.

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Bacterial decolourisation of textile dyes, primarily Reactive Black 5, was studied using Enterococcus faecalis and a range of environmental isolates. Textile dye decolourising strains of Shewanella, Pseudomonas and Clostridium were isolated from a textile company effluent. The environmental isolates decolourised a wider range of dyes (17/18) than E. faecalis (8/18).

Dye decolourisation rates were determined using Clostridium butyricum and E. faecalis with the four reactive dyes: Reactive Black, Procion Navy, Procion Crimson and Procion Yellow. Glucose was supplied as electron donor and the dyes were tested in their parent and hydrolysed forms. The azoreductase activity ranged from 0.8 to 51.7mg dye/h/g dry cell weight fox E. faecalis and 2.3 to 102.7mg dye/h/g dry cell weight for C. butyricum. The rates decreased in the order Reactive Black > Procion Yellow > Procion Navy > Procion Crimson, in both parent and hydrolysed forms. The initial decolourisation rate for hydrolysed Reactive Black was higher than for the parent dye (E faecalis-. 51.7 and 21.2 mg dye/h/g dry cell wt, C. butyricum: 102.7 and 59.0 mg dye/h/g dry cell wt for hydrolysed and parent dye respectively). This was probably due to differences in degree of sulphonation. Bacterial decolourisation of Reactive Black proceeded via an intermediate, most likely the hydrazo, to produce di-amino H-acid and a vinyl sulphone side chain.

Azoreductase was detected in cell free extracts of E. faecalis using non-denaturing gel electrophoresis. Two bands of azo reduction were observed on Reactive Black stained PAGE gels. One band had a molecular weight of 114.4 kDa, whereas the second band was probably chemical in origin. Both decolourisation bands were oxygen insensitive and required the addition of NADH for visualisation.

Toxic effects were apparent in the Vibrio fischeri Microtox test for decolourised Reactive Black (parent EC50 1.7-4.9ppm and hydrolysed EC50 0.15-0.25ppm). HPLC fractionation of decolourised hydrolysed Reactive Black samples demonstrated that the toxicity was due to the hydrolysed vinyl sulphone side chain which had an EC50 of 0.34ppm.

Item Type: Thesis
Creators: Kennerley, V.M.
Date: 2000
ISBN: 9781369316216
Divisions: Schools > School of Science and Technology
Record created by: Linda Sullivan
Date Added: 25 Sep 2020 13:55
Last Modified: 23 Aug 2023 13:17

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