Abstract
Simple SummaryAn efficient immobilized bacterial consortium of Raoultella planticola, Ochrobactrum thiophenivorans, Bacillus flexus, and Staphylococcus xylosus was used to degrade MO under high salinity conditions. The biodegradation efficiency was confirmed by UV−visible spectrophotometric analysis, FTIR, and the assaying of degradative enzymes. The cytotoxicity of such metabolic byproducts was evaluated on two human normal cell lines. In addition, the immobilized consortium showed the synergistic interaction between immobilized consortium and indigenous microorganism for degrading MO in artificially contaminated agricultural and industrial effluents.Methyl orange (MO) is categorized among the recalcitrant and refractory xenobiotics, representing a significant burden in the ecosystem. To clean-up the surrounding environment, advances in microbial degradation have been made. The main objective of this study was to investigate the extent to which an autochthonous consortium immobilized in alginate beads can promote an efficient biodegradation of MO. By employing response surface methodology (RSM), a parametric model explained the interaction of immobilized consortium (Raoultella planticola, Ochrobactrum thiophenivorans, Bacillus flexus and Staphylococcus xylosus) to assimilate 200 mg/L of MO in the presence of 40 g/L of NaCl within 120 h. Physicochemical analysis, including UV-Vis spectroscopy and FTIR, and monitoring of the degrading enzymes (azoreductase, DCIP reductase, NADH reductase, laccase, LiP, MnP, nitrate reductase and tyrosinase) were used to evaluate MO degradation. In addition, the toxicity of MO-degradation products was investigated by means of phytotoxicity and cytotoxicity. Chlorella vulgaris retained its photosynthetic performance (>78%), as shown by the contents of chlorophyll-a, chlorophyll-b and carotenoids. The viability of normal lung and kidney cell lines was recorded to be 90.63% and 99.23%, respectively, upon exposure to MO-metabolic outcomes. These results reflect the non-toxicity of treated samples, implying their utilization in ferti-irrigation applications and industrial cooling systems. Moreover, the immobilized consortium was employed in the bioremediation of MO from artificially contaminated agricultural and industrial effluents, in augmented and non-augmented systems. Bacterial consortium remediated MO by 155 and 128.5 mg/L in augmented systems of agricultural and industrial effluents, respectively, within 144 h, revealing its mutual synergistic interaction with both indigenous microbiotas despite differences in their chemical, physical and microbial contents. These promising results encourage the application of immobilized consortium in bioaugmentation studies using different resources.
Highlights
The genetic diversity and wealthy nature of microbial metabolism are considered the paramount agents in its governing several vital medical, pharmaceutical, agricultural, environmental and industrial applications
The current study focused on the biodegradation of Methyl orange (MO), as one of the most extensively used hazardous anionic azo dyes [45]
MO was assimilated by the examined consortium and 30% of it was eliminated during 7 days of incubation at the basal mineral salt medium (MSM), where it consumed MO as a carbon source and attacked its structure to obtain enough energy for survival and proliferation
Summary
The genetic diversity and wealthy nature of microbial metabolism are considered the paramount agents in its governing several vital medical, pharmaceutical, agricultural, environmental and industrial applications. Either bacterial [1] or mycoremediation [2], several man-made complicated xenobiotic compounds are degraded to simpler inorganic constituents or even mineralized into water and carbon dioxide Such a naturally occurring phenomenon offers many advantages over physical and chemical methods, including eco-friendliness, cost-effectiveness and less sludge generation or incomplete degraded byproducts, which represent additional environmental burdens [3,4]. Bioaugmentation is the addition of exogenous microorganisms, characterized by their biodegradation capacities, to indigenous or in situ microbial populations for improving the treatment process of pollutants [7]. The success in this task is mostly based on the proliferative and competitional proficiency of the introduced microbes [8]. Adjusting and monitoring some parameters such as temperature, pH, dissolved oxygen, nutrition availability, toxicity and microbial pressures during the treatment process contributes to its success; otherwise, it fails, as revealed in [10]
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