Textile effluent biodegradation potentials of textile effluent-adapted and non-adapted bacteria

Environmental pollution has been recognized as one of the major problems of the modern world. The increasing demand for water and the dwindling supply has made the treatment and reuse of industrialeffluents an attractive option. Textile effluents are of concern because they colour the drains and ultimately the water bodies. They also diminish the water quality. The ability of microorganisms todegrade and metabolize a wide variety of compounds has been recognized and exploited in various biotreatment processes. This study investigated the potential of bacteria isolated from textile industrieswastewater and drains (textile effluent adapted bacteria) and isolates from a municipal landfill (effluent non-adapted bacteria). We discovered effluent adapted strains of Acinetobacter, Bacillus and Legionellawith potentials for colour removal and strains of Acinetobacter, Bacillus and Pseudomonas with chemical oxygen demand (COD) removal activities. Only strains of Bacillus with potentials for use incolour and COD removal were isolated from the landfill. Plasmid screening did not reveal the presence of plasmids in the isolates. Thus the involvement of extra-chromosomal genes is not suggested. Inconclusion, as a preliminary step in the development of textile effluent biotreatment using indigenous microbes, we have discovered some strains with potency to decolourize and/or remove COD

Characterization of an Alkali- and Halide-Resistant Laccase Expressed in E. coli: CotA from <i>Bacillus clausii</i>

The limitations of fungal laccases at higher pH and salt concentrations have intensified the search for new extremophilic bacterial laccases. We report the cloning, expression, and characterization of the bacterial cotA from Bacillus clausii, a supposed alkalophilic ortholog of cotA from B. subtilis. Both laccases were expressed in E. coli strain BL21(DE3) and characterized fully in parallel for strict benchmarking. We report activity on ABTS, SGZ, DMP, caffeic acid, promazine, phenyl hydrazine, tannic acid, and bilirubin at variable pH. Whereas ABTS, promazine, and phenyl hydrazine activities vs. pH were similar, the activity of B. clausii cotA was shifted upwards by ~0.5-2 pH units for the simple phenolic substrates DMP, SGZ, and caffeic acid. This shift is not due to substrate affinity (K(M)) but to pH dependence of catalytic turnover: The k(cat) of B. clausii cotA was 1 s⁻¹ at pH 6 and 5 s⁻¹ at pH 8 in contrast to 6 s⁻¹ at pH 6 and 2 s⁻¹ at pH 8 for of B. subtilis cotA. Overall, k(cat)/K(M) was 10-fold higher for B. subtilis cotA at pH(opt). While both proteins were heat activated, activation increased with pH and was larger in cotA from B. clausii. NaCl inhibited activity at acidic pH, but not up to 500-700 mM NaCl in alkaline pH, a further advantage of the alkali regime in laccase applications. The B. clausii cotA had ~20 minutes half-life at 80°C, less than the ~50 minutes at 80°C for cotA from B. subtilis. While cotA from B. subtilis had optimal stability at pH~8, the cotA from B. clausii displayed higher combined salt- and alkali-resistance. This resistance is possibly caused by two substitutions (S427Q and V110E) that could repel anions to reduce anion-copper interactions at the expense of catalytic proficiency, a trade-off of potential relevance to laccase optimization

Single-route delaminated clay composites for efficient visible-light photo-mineralization of antibiotic-resistant bacteria and associated genes in water

Drinking water contaminated with antibiotic resistant bacteria could result in loss of antibiotic effectiveness in humans, increased healthcare cost and ultimately death. New delaminated photocatalytic composite (DPC) has been prepared. DPC doped with Cu/Zn kept multidrug resistant (MDR) E. coli and its sulphonamide resistance genes in contaminated water at log reduction >6 for 36 h in two disinfection steps under visible-light using fixed-bed mode (downward flow). In contrast, fluoroquinolone resistance genes persisted in treated water after the first disinfection step and were significantly reduced after the second disinfection step. Surface oxygen vacancies were mainly responsible for photoactivity of DPC. No bacteria re-growth was observed in treated water stored in light/dark for 7 days. A 95 % photo-mineralisation of MDR E. coli and its genes was achieved via the release of superoxide radical (in dark/light). Shelf-life study of DPC vs non-delaminated photocatalytic composite over 7 months suggests that the former remained far more efficient than the latter