Wasteful Azo Dyes as a Source of Biologically Active Building Blocks

Abstract

In this work, an environment-friendly enzymatic strategy was developed for the valorisation of dye-containing wastewaters. We set up biocatalytic processes for the conversion of azo dyes representative of the main classes used in the textile industry into valuable aromatic compounds: aromatic amines, phenoxazinones, phenazines, and naphthoquinones. First, purified preparations of PpAzoR azoreductase efficiently reduced mordant, acid, reactive, and direct azo dyes into aromatic amines, and CotA-laccase oxidised these compounds into phenazines, phenoxazinones, and naphthoquinones. Second, whole cells containing the overproduced enzymes were utilised in the two-step enzymatic conversion of the model mordant black 9 dye into sodium 2-amino-3-oxo-3H-phenoxazine-8-sulphonate, allowing to overcome the drawbacks associated with the use of expensive purified enzymes, co-factors, or exquisite reaction conditions. Third, cells immobilised in sodium alginate allowed recycling the biocatalysts and achieving very good to excellent final phenoxazine product yields (up to 80%) in water and with less impurities in the final reaction mixtures. Finally, one-pot systems using recycled immobilised cells co-producing both enzymes resulted in the highest phenoxazinone yields (90%) through the sequential use of static and stirring conditions, controlling the oxygenation of reaction mixtures and the successive activity of azoreductase (anaerobic) and laccase (aerobic).

Rationally Guided Improvement of NOV1 Dioxygenase for the Conversion of Lignin-Derived Isoeugenol to Vanillin

“…Remarkably, the k cat of the S283F variant for isoeugenol is 2–10 times higher than the values previously reported for isoeugenol oxygenases, ,,, further endorsing this enzyme as a superior biocatalyst at nonlimiting substrate concentrations, typical of industrial setups. We set up time-course bioconversion assays using whole cells that overproduced the S283F variant to reduce the costs associated with enzyme purification (Figure B,C). , Our results revealed that excellent molar conversion yields (>99%) were achievable within 24 h of reaction using ≤100 mM isoeugenol in the presence of small amounts (3.5%) of ethanol, a biosolvent, in the whole cell catalysis mixture.…”

Genotoxicity of Synthetic Food Colors on Nitrogen-Fixing Bacteria in Agricultural Lands Irrigated with Wastewater of Corresponding Industries

“…Several confectioners also contain unidentified colors, such as textile dyes [2]. In addition, different industrial wastewater contains synthetic dyes or food colors in which almost 70% of azo dyes contain one or more azo bonds (R 1 -N-N-R 2 ) in their chemical structure [61]. Some synthetic food colors are reported to contain carcinogenic chemicals, such as β-naphthylamine (which is also known as 2-naphthylamine), carrying the amino group at position two [62,63].…”

Analysis of the feasibility of using biopolymers of different viscosities as immobilization carriers for laccase in synthetic dye removal

“…-N = N-, = C = O, C-NH, CH = N-, C-S) in their structures (Islam et al 2021). Most dyes are toxic, mutagenic and carcinogenic to living organisms (Fernandes et al 2021), highlighting the pressing need for sustainable water management practices, including water reuse and the adoption of circular economy principles to eliminate of toxic compounds, including dyes (Al-Tohamy et al 2022). Notably, dyes commonly used in industrial applications, such as indigo carmine (IC) and methylene blue (MB), among others, are of particular concern.…”