2. Introduction
Dyes are organic chemical compounds, which impart colour to other
materials by saturating them in aqueous solution. Synthetic dyes
have a wide application in the food, pharmaceutical, textile, leather,
cosmetics and paper industries due to their ease of production,
fastness and variety in colour compared to natural dyes. Dyes are
designed to remain stable and long-lasting colorants which are
usually not easily biodegraded.
Azo dyes are considered as electron-
deficient xenobiotic compounds because they possess azo bond
(R1–N=N–R2) and other electron-withdrawing groups, generating
electron deficiency in the molecule and making the compound less
susceptible to oxidative catabolism by bacteria. As a consequence,
azo dyes tend to persist under aerobic environmental conditions.
Abhishek Jaiswal
3. Objectives
• To study the mediated decolourization of RV5 by
Stenotrophomonas maltophilia.
• To optimize physico-chemical parameter for efficient AQS-mediated
RV5 decolourization.
• To determine quinone reductase in Stenotrophomonas maltophilia
grown in presence of dye and AQS.
• To demonstrate degradation of RV5 by Stenotrophomonas
maltophilia using thin layer chromatography.
Abhishek Jaiswal
4. Materials and methods
Stenotrophomonas maltophilia was already isolated in our laboratory and
maintained on Luria Bertani (LB) medium. Decolorization of reactive violet 5
(RV5) was performed in modified Bushnell and Hass Mineral (BHM).
Overnight grown culture of S. maltophilia was
inoculated in 100 mL liquid medium in 250 mL Erlenmeyer flasks and
incubated at 37 o
C under static condition. 2 mL of samples were withdrawn
at regular time interval up to complete dye decolorization. Growth of culture
was measured at 660 nm and RV5 color was measured at 558 nm. The
percent decolorization and decolorization rate were calculated as follow:
Decolorization (%) = (Initial dye concentration – final dye concentration) × 100
Initial dye concentration
Decolorization rate (mg/L.h) = Initial dye concentration – Final dye concentration (mg/L)
Time withdrawn for decolorization (h)
Abhishek Jaiswal
15. Effect of RV5 and glucose on AQS mediated RV5 decolorization
Abhishek Jaiswal
16. Effect of RV5 and yeast extract (YE) on AQS-mediated RV5
decolorization
Abhishek Jaiswal
17. Quinine reductase activity of Stenotrophomonas maltophilia
grown in presence and absence of AQS (1mM) and RV5 (50 mg/L)
Abhishek Jaiswal
18. Thin Layer Chromatogram of RV5 and degraded metabolites of
RV5 (L1: Abiotic RV5 control, L2: Decolorized RV5)
L1 L2
Abhishek Jaiswal
19. Summary and conclusion
• Mediated decolorization of reactive violet 5 by Stenotrophomonas
maltophilia under static condition was investigated. Different redox
mediators used during this work were anthraquinone-2-sulphonate,
anthraquinone-2, 6-disulphonate, lawsone and ethyl viologen in
which AQS was found to be most suitable for efficient dye
decolorization.
• The maximum decolorization rate of RV5 by S. maltophilia was
observed in presence of 2 mM AQS in medium containing 0.05 %
(w/v) glucose, 0.05 % (w/v) yeast extract, 20 mM KNO3 as inorganic
nitrogen source, initial pH 7.5 and an inoculum size of 0.1 O.D.660 nm
under static incubation at 37 ºC.
• Increase in intracellular quinine reductase activity was observed in
presence of AQS, suggesting its role in reduction of AQS to AQSH2,
which may be ultimately involved in reduction of RV5.
• Degradation of RV5 could be demonstrated by silica gel thin layer
chromatography.
Abhishek Jaiswal
