R software package based statistical optimization of process components to simultaneously enhance the bacterial growth, laccase production and textile dye decolorization with cytotoxicity study.

Sunil Bhavsar,Pravin Dudhagara,Shantilal Tank,Rafael Vazquez-Duhalt

doi:10.1371/journal.pone.0195795

Sunil Bhavsar, Pravin Dudhagara + Show 2 more

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https://doi.org/10.1371/journal.pone.0195795

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Journal: PloS one	Publication Date: May 2, 2018
Citations: 23	License type: CC BY 4.0

Affiliation: Veer Narmad South Gujarat University

Abstract

The thermophilic bacterium, Bacillus licheniformis U1 is used for the optimization of bacterial growth (R1), laccase production (R2) and synthetic disperse blue DBR textile dye decolorization (R3) in the present study. Preliminary optimization has been performed by one variable at time (OVAT) approach using four media components viz., dye concentration, copper sulphate concentration, pH, and inoculum size. Based on OVAT result further statistical optimization of R1, R2 and R3 performed by Box–Behnken design (BBD) using response surface methodology (RSM) in R software with R Commander package. The total 29 experimental runs conducted in the experimental design study towards the construction of a quadratic model. The model indicated that dye concentration 110 ppm, copper sulphate 0.2 mM, pH 7.5 and inoculum size 6% v/v were found to be optimum to maximize the laccase production and bacterial growth. Whereas, maximum dye decolorization achieved in media containing dye concentration 110 ppm, copper sulphate 0.6 mM, pH 6 and inoculum size 6% v/v. R package predicted R2 of R1, R2 and R3 were 0.9917, 0.9831 and 0.9703 respectively; likened to Design-Expert (Stat-Ease) (DOE) predicted R2 of R1, R2, and R3 were 0.9893, 0.9822 and 0.8442 respectively. The values obtained by R software were more precise, reliable and reproducible, compared to the DOE model. The laccase production was 1.80 fold increased, and 2.24 fold enhancement in dye decolorization was achieved using optimized medium than initial experiments. Moreover, the laccase-treated sample demonstrated the less cytotoxic effect on L132 and MCF-7 cell lines compared to untreated sample using MTT assay. Higher cell viability and lower cytotoxicity observed in a laccase-treated sample suggest the impending application of bacterial laccase in the reduction of toxicity of dye to design rapid biodegradation process.

Highlights

Synthetic dyes and dyestuff extensively use in textile, paper, cosmetic and pharmaceutical industries
Anaerobic azo dye reduction resulting in the formation of toxic aromatic amines which are not mineralized anaerobically [10], except a few toxic aromatic amines substituted with hydroxyl and carboxyl groups degrade under methanogen conditions [11]
The first step takes in reductive cleavage of the dyes azo linkages, resulting in the formation of usually colourless but potentially hazardous aromatic amines remains which degraded in a second step [30]

Summary

Introduction

Synthetic dyes and dyestuff extensively use in textile, paper, cosmetic and pharmaceutical industries. Textile industries in developing countries showed a significant increase in the use of synthetic organic dyes as the coloring agent. Anaerobic azo dye reduction resulting in the formation of toxic aromatic amines which are not mineralized anaerobically [10], except a few toxic aromatic amines substituted with hydroxyl and carboxyl groups degrade under methanogen conditions [11]. Azo dyes are resistant to bacterial attack under aerobic condition [13,14,15,16,17] because the presence of oxygen usually inhibits azo bond reduction activity. The first step takes in reductive cleavage of the dyes azo linkages, resulting in the formation of usually colourless but potentially hazardous aromatic amines remains which degraded in a second step [30]

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