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Textile effluent generated during the dyeing process of textiles is a huge supplier to water toxicity all over the world. Textile dyes are the main toxic component found in the effluent sample which is difficult to treat. A bacterial consortium capable of decolourizing and degrading the textile dye acid orange is reported in this research article. The bacterial consortium was identified by 16 S rDNA sequence and phenotypic characteristics. It is composed of four strains i.e., Pseudomonas stutzeri (MW219251), Bacillus tequilensis (MW110471), Bacillus flexus (MW131645), Kocuria rosea (MW132411). The consortium was able to cause decolorization of azo dye acid orange (30 mg/L) in 23 h, when kept under static laboratory conditions. The optimal pH and temperature for color removal were pH 7.5 and 32°C, respectively. The decolorization of dye before and after was checked by UV-Visible absorption spectra. This gives evidence that decolorization was caused due to biodegradation. This was further assured by studying the reduction of biological oxygen demand (BOD5 (96%), chemical oxygen demand (COD) (79%), and TOC (total organic carbon) (54%) of the bacterial-treated water sample. The Fourier transform-infrared spectroscopy (FT-IR) spectroscopy and gas chromatography-mass spectroscopy (GC-MS) results confirmed the mineralization of the dye. The results indicate the effectiveness of the bacterial consortium SPB92 in the biodegradation of acid orange dye. This demonstrates that the consortium has immense potential and will serve as an important contributor to the treatment of textile wastewater.

Heavy metal polluted wastewater from industries is currently one of the major environmental concerns leading to insufficient supply of clean water. Several strategies have been implemented to overcome this challenge including the use of microalgae as heavy metal bio-removers. However, there are still limitations that prevent microalgae to function optimally. Synthetic biology is a new biological discipline developed to solve challenging problems via bioengineering approaches. To date, synthetic biology has no universally affirmed definitions; however, it is uncontroversial that synthetic biology utilizes a constructive library of genetic standardized parts to create new biological systems or to redesign existing ones with improved characteristics. In this mini-review, we present state-of-the-art synthetic biology-based approaches that can be used to enhance heavy metal bio-removal from wastewater effluents by microalgae with a narrative synthetic biology workflow (Design-Build-Test-Learn cycle) to guide future developments of more advanced systems. We also provide insights into potent genes and proteins responsible for the bio-removal processes for stepwise developments of more advanced systems. A total of 49 unique genes and proteins are listed based on their eight heavy metals (Mn, Fe, Cu, Zn, As, Cd, Hg, and Pb) bio-removal functions in transport system, cellular tolerance, synthesis of key players in heavy metal bio-removal, biotransformation of heavy metals, and gene expression regulation. Thus, with our library, genetic parts are ready to be recruited for any synthetic biology-based designs. Thereby, this mini-review identifies potential avenues of future research and maps opportunities to unleash more potential of microalgae as heavy metal bio-removers with synthetic biology.

Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.