1.Structural insights into 2,2'-azino-Bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)-mediated degradation of reactive blue 21 by engineered Cyathus bulleri Laccase and characterization of degradation products.
Kenzom T1, Srivastava P1, Mishra S2. Appl Environ Microbiol. 2014 Dec;80(24):7484-95. doi: 10.1128/AEM.02665-14. Epub 2014 Sep 26.
Advanced oxidation processes are currently used for the treatment of different reactive dyes which involve use of toxic catalysts. Peroxidases are reported to be effective on such dyes and require hydrogen peroxide and/or metal ions. Cyathus bulleri laccase, expressed in Pichia pastoris, catalyzes efficient degradation (78 to 85%) of reactive azo dyes (reactive black 5, reactive orange 16, and reactive red 198) in the presence of synthetic mediator ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)]. This laccase was engineered to degrade effectively reactive blue 21 (RB21), a phthalocyanine dye reported to be decolorized only by peroxidases. The 816-bp segment (toward the C terminus) of the lcc gene was subjected to random mutagenesis and enzyme variants (Lcc35, Lcc61, and Lcc62) were selected based on increased ABTS oxidizing ability. Around 78 to 95% decolorization of RB21 was observed with the ABTS-supplemented Lcc variants in 30 min.
2.Anaerobic biodecolorization of textile reactive anthraquinone and phthalocyanine dyebaths under hypersaline conditions.
Lee YH1, Matthews RD, Pavlostathis SG. Water Sci Technol. 2005;52(1-2):377-83.
The biological decolorization of two industrial, spent textile reactive dyebaths was investigated using a suspended-growth, halophilic mixed culture fed with glucose. Dyebath I contained mainly Reactive Blue 19 (RB19), an anthraquinone dye, whereas dyebath II contained mainly Reactive Blue 21 (RB21), a phthalocyanine dye. Batch assays under anaerobic conditions with the two neutralized dyebaths resulted in 87 and 37% extent of decolorization for dyebaths I and II, respectively. The rate of glucose utilization and the extent of acetate production were impacted in the presence of each dyebath as compared to the control culture. However, dyebath decolorization occurred despite moderate culture inhibition. Reuse of a biologically renovated RB19-containing dyebath in the dyeing process resulted in reproducible but not identical cotton fabric shades as compared to a standard dyeing (i.e., control) using fresh water. This difference is attributed to a variable degree of RB19 aggregation during the dyeing process and is not related to the efficiency of the biodecolorization process.
3.Decolorization of a mixture of textile dyes using Bjerkandera sp. BOL-13.
Nordström F1, Terrazas E, Welander U. Environ Technol. 2008 Aug;29(8):921-9. doi: 10.1080/09593330802131628.
The white-rot fungus Bjerkandera sp. BOL-13 was evaluated regarding decolorization of four textile dyes Reactive blue 21, Reactive black 5, Reactive orange 13 and Reactive yellow 206. Experiments were performed in batch and continuous modes. The total dye concentration in all experiments was 100 mg l(-1). The results of the batch experiments showed that the fungus decolorized all dyes but at different rates. There was, however, an increase in the ultraviolet (UV) absorbance when a medium with a low concentration of nitrogen was used. No increase in UV range was observed when the nitrogen concentration was increased. A continuous experiment was performed to study the decolorization of a mixture of three of the dyes Reactive blue 21, Reactive black 5 and Reactive orange 13. Scanning of inlet and outlet samples showed that the absorbance at the peaks in the visible range decreased by 60-66%. The UV absorbance of the outlet increased during the first days of operation after which it decreased again to reach the same level as the inlet.
4.Biopolymer capped silver nanoparticles with potential for multifaceted applications.
Vanamudan A1, Sudhakar PP2. Int J Biol Macromol. 2016 May;86:262-8. doi: 10.1016/j.ijbiomac.2016.01.056. Epub 2016 Jan 19.
A sustainable, green and low cost method for the synthesis of silver nanoparticles at room temperature has been developed using guargum as a reducing and stabilizing agent. The synthesized silver nanoparticles (GAg) were characterized by UV-vis spectroscopy, FTIR, EDS, Raman, XRD and TEM. The interaction of the functional groups present in the biopolymer Guargum (G) with the silver nanoparticles (GAg) were responsible for the nanoparticle surface to function as active substrates for Surface Enhanced Raman Spectroscopic (SERS) detection of cationic and anionic dyes. The catalytic degradation of a copper phthalocyanine based dye- Reactive blue - 21(RB-21), an azo dye- Reactive red 141(RR-141) and a xanthene dye- Rhodamine - 6G(Rh-6G) as well as binary mixtures of the three dyes was evaluated using the synthesized nanoparticles. The catalyst also caused a significant reduction in Total Organic Carbon (TOC) suggesting the formation of smaller degraded products.