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Pseudomonas extremorientalis BU118: a new salt-tolerant laccase-secreting bacterium with biotechnological potential in textile azo dye decolourization

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ABSTRACT

The present investigation focused on screening of a new potent strain for laccase production and optimizing the process parameters to achieve the maximum enzymatic decolourization of textile azo dye Congo red. Seven hydrocarbonoclastic bacterial strains were selected as positive in laccase production in solid medium using 2,6 dimethoxyphenol as an enzyme activity indicator. The best enzyme producer Pseudomonasextremorientalis BU118 showed a maximum laccase activity of about 7000 U/L of wheat bran under solid-state conditions. The influence of different concentrations of dye, enzyme, salt and various incubation times on Congo red decolourization was studied using response surface methodology to find the optimum conditions required for maximum decolourization by P.extremorientalis laccase. The enzyme exhibited a remarkable colour removal capability over a wide range of dye and salt concentrations. The above results show the potential use of this bacterial laccase in the biological treatment of the textile effluent.

No MeSH data available.


Contour and response surface plots of Congo red decolourization by P.extremorientalis laccase as a function of: a enzyme concentration (X1) and dye concentration (X2) levels at midlevel of NaCl concentration (2.5 %) and incubation time (14 h); b enzyme concentration (X1) and NaCl concentration (X3) levels at midlevel of dye concentration (150 mg/l) and incubation time (14 h); c dye concentration (X2) and NaCl concentration (X3) levels at midlevel of enzyme concentration (0.6 U/ml) and incubation time (14 h); d dye concentration (X2) and incubation time (X4) levels at midlevel of enzyme concentration (0.6 U/ml) and NaCl concentration (2.5 %)
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Fig3: Contour and response surface plots of Congo red decolourization by P.extremorientalis laccase as a function of: a enzyme concentration (X1) and dye concentration (X2) levels at midlevel of NaCl concentration (2.5 %) and incubation time (14 h); b enzyme concentration (X1) and NaCl concentration (X3) levels at midlevel of dye concentration (150 mg/l) and incubation time (14 h); c dye concentration (X2) and NaCl concentration (X3) levels at midlevel of enzyme concentration (0.6 U/ml) and incubation time (14 h); d dye concentration (X2) and incubation time (X4) levels at midlevel of enzyme concentration (0.6 U/ml) and NaCl concentration (2.5 %)

Mentions: Interactions between the studied variables for Congo red dye decolourization are shown in 3D and 2D contour plots (Fig. 3a–d). These plots show the Congo red decolourization as function of two factors, while the others were fixed at zero level. 3D and 2D contour plots for the interaction effect of enzyme and dye concentrations towards dye decolourization are shown in Fig. 3a. The results indicate that the response increased on increasing the enzyme concentration and decreasing the dye concentration. The decreasing dye decolourization at higher concentrations was probably a result of possible enzyme inactivation at such high dye levels. The behaviour of percentage decolourization with respect to changes in enzyme and salt concentrations is shown in Fig. 3b. These two parameters showed positive influence on dye decolourization. The percentage dye decolourization increased with increase in salt concentration and enzyme concentration until a certain level, where further increases in both parameters led to nonsignificant change in dye decolourization. Figure 3c represents the effect of varying NaCl and dye concentrations at fixed levels of enzyme concentration and incubation time. The response plot revealed that an increase in salt concentration increased the decolourization level. However, the rate of decolourization decreased with the increase in dye concentration. Figure 3d represents the effect of varying concentrations of dye at different incubation times on Congo red decolourization under 0.6 U/L enzyme and 1.1 mM salt concentrations. The results indicate globally that the response increased with the increase in the reaction time and decrease in the dye concentration and vice versa.Fig. 3


Pseudomonas extremorientalis BU118: a new salt-tolerant laccase-secreting bacterium with biotechnological potential in textile azo dye decolourization
Contour and response surface plots of Congo red decolourization by P.extremorientalis laccase as a function of: a enzyme concentration (X1) and dye concentration (X2) levels at midlevel of NaCl concentration (2.5 %) and incubation time (14 h); b enzyme concentration (X1) and NaCl concentration (X3) levels at midlevel of dye concentration (150 mg/l) and incubation time (14 h); c dye concentration (X2) and NaCl concentration (X3) levels at midlevel of enzyme concentration (0.6 U/ml) and incubation time (14 h); d dye concentration (X2) and incubation time (X4) levels at midlevel of enzyme concentration (0.6 U/ml) and NaCl concentration (2.5 %)
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Related In: Results  -  Collection

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Fig3: Contour and response surface plots of Congo red decolourization by P.extremorientalis laccase as a function of: a enzyme concentration (X1) and dye concentration (X2) levels at midlevel of NaCl concentration (2.5 %) and incubation time (14 h); b enzyme concentration (X1) and NaCl concentration (X3) levels at midlevel of dye concentration (150 mg/l) and incubation time (14 h); c dye concentration (X2) and NaCl concentration (X3) levels at midlevel of enzyme concentration (0.6 U/ml) and incubation time (14 h); d dye concentration (X2) and incubation time (X4) levels at midlevel of enzyme concentration (0.6 U/ml) and NaCl concentration (2.5 %)
Mentions: Interactions between the studied variables for Congo red dye decolourization are shown in 3D and 2D contour plots (Fig. 3a–d). These plots show the Congo red decolourization as function of two factors, while the others were fixed at zero level. 3D and 2D contour plots for the interaction effect of enzyme and dye concentrations towards dye decolourization are shown in Fig. 3a. The results indicate that the response increased on increasing the enzyme concentration and decreasing the dye concentration. The decreasing dye decolourization at higher concentrations was probably a result of possible enzyme inactivation at such high dye levels. The behaviour of percentage decolourization with respect to changes in enzyme and salt concentrations is shown in Fig. 3b. These two parameters showed positive influence on dye decolourization. The percentage dye decolourization increased with increase in salt concentration and enzyme concentration until a certain level, where further increases in both parameters led to nonsignificant change in dye decolourization. Figure 3c represents the effect of varying NaCl and dye concentrations at fixed levels of enzyme concentration and incubation time. The response plot revealed that an increase in salt concentration increased the decolourization level. However, the rate of decolourization decreased with the increase in dye concentration. Figure 3d represents the effect of varying concentrations of dye at different incubation times on Congo red decolourization under 0.6 U/L enzyme and 1.1 mM salt concentrations. The results indicate globally that the response increased with the increase in the reaction time and decrease in the dye concentration and vice versa.Fig. 3

View Article: PubMed Central - PubMed

ABSTRACT

The present investigation focused on screening of a new potent strain for laccase production and optimizing the process parameters to achieve the maximum enzymatic decolourization of textile azo dye Congo red. Seven hydrocarbonoclastic bacterial strains were selected as positive in laccase production in solid medium using 2,6 dimethoxyphenol as an enzyme activity indicator. The best enzyme producer Pseudomonasextremorientalis BU118 showed a maximum laccase activity of about 7000 U/L of wheat bran under solid-state conditions. The influence of different concentrations of dye, enzyme, salt and various incubation times on Congo red decolourization was studied using response surface methodology to find the optimum conditions required for maximum decolourization by P.extremorientalis laccase. The enzyme exhibited a remarkable colour removal capability over a wide range of dye and salt concentrations. The above results show the potential use of this bacterial laccase in the biological treatment of the textile effluent.

No MeSH data available.