Abstract
The application of microorganisms in azo dye remediation has gained significant attention, leading to various published studies reporting different methods for obtaining the best dye decolouriser. This paper investigates and compares the role of methods and media used in obtaining a bacterial consortium capable of decolourising azo dye as the sole carbon source, which is extremely rare to find. It was demonstrated that a prolonged acclimation under low substrate availability successfully isolated a novel consortium capable of utilising Reactive Red 120 dye as a sole carbon source in aerobic conditions. This consortium, known as JR3, consists of Pseudomonas aeruginosa strain MM01, Enterobacter sp. strain MM05 and Serratia marcescens strain MM06. Decolourised metabolites of consortium JR3 showed an improvement in mung bean’s seed germination and shoot and root length. One-factor-at-time optimisation characterisation showed maximal of 82.9% decolourisation at 0.7 g/L ammonium sulphate, pH 8, 35 °C, and RR120 concentrations of 200 ppm. Decolourisation modelling utilising response surface methodology (RSM) successfully improved decolourisation even more. RSM resulted in maximal decolourisation of 92.79% using 0.645 g/L ammonium sulphate, pH 8.29, 34.5 °C and 200 ppm RR120.
Highlights
Azo dyes account for 70% of the 9.9 million tons of industrial dye used annually, with a global turnover valued at USD 30.42 billion [1,2]
This result is in agreement with the previously reported Reactive Red 120 (RR120) maximum absorbance, which is within the range of 525 ± 10 nm [26,30]
This study illustrates that a long period of slow acclimation process led to the isolation of bacterial strains capable of utilising RR120 as a sole carbon source without the presence of additional carbon or co-substate
Summary
Azo dyes account for 70% of the 9.9 million tons of industrial dye used annually, with a global turnover valued at USD 30.42 billion [1,2]. Most of the dyes synthesised contain azo compounds and are predominantly used in textile, paper, food, printing, cosmetic and leather industries [3]. Certain azo dyes contain chemical groups, which have a high affinity for metal ions [5]. These enhanced properties provide a high degree of chemical, biological and photocatalytic stability. Reactive Red 120 (RR120) is one of the widely used dyes in the textile industry due to it providing a high degree of chemical, biological and photocatalytic stabilities [1]. Their resistance to breakdown due to time, exposure to sunlight, detergents, water and microorganisms results in poor degradation in the environment [6]
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