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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.

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a Petriplate showing Pseudomonasextremorientalis BU118 grown in 2,6-dimethoxyphenol-supplemented solid medium. The production of an intense brown colour is considered as a positive reaction for the presence of laccase activity. b Phylogenetic analysis of 16S rRNA gene sequence of bacterial isolate P.extremorientalis strain BU118 based on 16S rDNA partial sequences. Phylogenetic dendrogram was evaluated by performing bootstrap analysis of 1000 data sets using MEGA 6.06 software. 16S rRNA sequence accession numbers of the reference strains are indicated in parentheses
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Fig1: a Petriplate showing Pseudomonasextremorientalis BU118 grown in 2,6-dimethoxyphenol-supplemented solid medium. The production of an intense brown colour is considered as a positive reaction for the presence of laccase activity. b Phylogenetic analysis of 16S rRNA gene sequence of bacterial isolate P.extremorientalis strain BU118 based on 16S rDNA partial sequences. Phylogenetic dendrogram was evaluated by performing bootstrap analysis of 1000 data sets using MEGA 6.06 software. 16S rRNA sequence accession numbers of the reference strains are indicated in parentheses

Mentions: Hydrocarbonoclastic bacteria previously isolated from petroleum-contaminated sediments in Tunisia (Mahjoubi et al. 2013) were screened for laccase activity on solid media containing DMP as an indicator compound (YunYang et al. 2008). The formation of brown colour around the colonies after incubation at 30 °C for 4 days indicated the presence of the laccase enzyme. The colour intensity varies due to the variability in the concentration of laccase production (Amutha and Abhijit 2015). On the basis of this screening, seven potential species belonging to six genera designated as Achromobacterxylosoxidans BU22, Acinetobactervenetianus BU19, Acinetobacterbeijerinckii BU45, Luteibacterrhizovicinus BU33, Gordoniaamicalis BU147, Ochrobactrumgrignonense BU72 and P.extremorientalis BU118, showed positive laccase activities. Out of seven, the laccase-positive isolate, P.extremorientalis BU118, was found to be the most potential isolate producing laccase on the basis of DMP oxidation in the plate screening test (Table 2; Fig. 1a). Therefore, BU118 was selected for further investigation based on the highest enzyme activity. The phylogenetic tree obtained when the 16s RNA gene sequence of the organism was analysed is shown in Fig. 1b. Bacterial laccase producers belonging to the Pseudomonas species have been previously described for P.putida (McMahon et al. 2007; Kuddus et al. 2013), P.fluorescens (Vandana and Peter 2014), P.aeruginosa (Peter and Vandana 2014) and P. desmolyticum (Kalme et al. 2009).Table 2


Pseudomonas extremorientalis BU118: a new salt-tolerant laccase-secreting bacterium with biotechnological potential in textile azo dye decolourization
a Petriplate showing Pseudomonasextremorientalis BU118 grown in 2,6-dimethoxyphenol-supplemented solid medium. The production of an intense brown colour is considered as a positive reaction for the presence of laccase activity. b Phylogenetic analysis of 16S rRNA gene sequence of bacterial isolate P.extremorientalis strain BU118 based on 16S rDNA partial sequences. Phylogenetic dendrogram was evaluated by performing bootstrap analysis of 1000 data sets using MEGA 6.06 software. 16S rRNA sequence accession numbers of the reference strains are indicated in parentheses
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835423&req=5

Fig1: a Petriplate showing Pseudomonasextremorientalis BU118 grown in 2,6-dimethoxyphenol-supplemented solid medium. The production of an intense brown colour is considered as a positive reaction for the presence of laccase activity. b Phylogenetic analysis of 16S rRNA gene sequence of bacterial isolate P.extremorientalis strain BU118 based on 16S rDNA partial sequences. Phylogenetic dendrogram was evaluated by performing bootstrap analysis of 1000 data sets using MEGA 6.06 software. 16S rRNA sequence accession numbers of the reference strains are indicated in parentheses
Mentions: Hydrocarbonoclastic bacteria previously isolated from petroleum-contaminated sediments in Tunisia (Mahjoubi et al. 2013) were screened for laccase activity on solid media containing DMP as an indicator compound (YunYang et al. 2008). The formation of brown colour around the colonies after incubation at 30 °C for 4 days indicated the presence of the laccase enzyme. The colour intensity varies due to the variability in the concentration of laccase production (Amutha and Abhijit 2015). On the basis of this screening, seven potential species belonging to six genera designated as Achromobacterxylosoxidans BU22, Acinetobactervenetianus BU19, Acinetobacterbeijerinckii BU45, Luteibacterrhizovicinus BU33, Gordoniaamicalis BU147, Ochrobactrumgrignonense BU72 and P.extremorientalis BU118, showed positive laccase activities. Out of seven, the laccase-positive isolate, P.extremorientalis BU118, was found to be the most potential isolate producing laccase on the basis of DMP oxidation in the plate screening test (Table 2; Fig. 1a). Therefore, BU118 was selected for further investigation based on the highest enzyme activity. The phylogenetic tree obtained when the 16s RNA gene sequence of the organism was analysed is shown in Fig. 1b. Bacterial laccase producers belonging to the Pseudomonas species have been previously described for P.putida (McMahon et al. 2007; Kuddus et al. 2013), P.fluorescens (Vandana and Peter 2014), P.aeruginosa (Peter and Vandana 2014) and P. desmolyticum (Kalme et al. 2009).Table 2

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.


Related in: MedlinePlus