Solar-light-active mesoporous Cr-TiO2 for photodegradation of spent wash: an in-depth study using QTOF LC-MS.

A dark-coloured effluent called "spent wash" is generated as an unwanted product in sugarcane-based alcohol distilleries. Most distilleries discharge this effluent into soil or water without any treatment, causing water and soil pollution. Herein, we report chromium-doped TiO2 (Cr-TiO2) as a photocatalyst for the degradation of spent wash colour under natural sunlight. Cr-doped TiO2 nanoparticles were prepared using an aqueous titanium peroxide-based sol-gel method with titanium isopropoxide as the Ti precursor and chromium nitrate as the Cr precursor. To observe the effect of dopant on sol-gel behaviour and physicochemical properties, the Cr concentration was varied in the range 0.5-5 wt%. The crystallization temperature and time were optimized to obtain the required phase of Cr-TiO2. The physicochemical characteristics of the Cr-doped TiO2 catalyst were determined using X-ray diffraction, FE-SEM, FETEM, TG, XPS, the Brunauer-Emmett-Teller (BET) method, FT-IR, Raman, PL, ICP-MS, and UV visible spectroscopy. A shift in the absorption edge of TiO2 by doping with chromium suggested an increase in visible light absorption due to a decrease in the effective band gap. The application potential of the Cr-TiO2 catalyst was studied in the degradation of sugar-based alcohol distillery waste under natural sunlight, and the results were compared with those of undoped TiO2 and Degussa P25 TiO2. Degradation of the spent wash solution was monitored using UV-visible, gel permeation chromatography (GPC), and QTOF LC-MS. GPC and LC-MS showed significant changes in the molecular weight of spent wash colour-forming compounds due to the degradation reaction. QTOF LC-MS analysis suggested that acids, alcohols, glucosides, ketones, lipids, peptides, and metabolites were oxidized to low-molecular-weight counterparts. From the results, 5% Cr-TiO2 showed the highest degradation rate among all Cr-TiO2 samples, undoped TiO2, and Degussa P25 TiO2 under identical reaction conditions, with nearly 68-70% degradation achieved in 5 h.

Batch and continuous biodegradation of Amaranth in plain distilled water by P. aeruginosa BCH and toxicological scrutiny using oxidative stress studies.

Bacterium Pseudomonas aeruginosa BCH was able to degrade naphthylaminesulfonic azo dye Amaranth in plain distilled water within 6 h at 50 mg l(-1) dye concentration. Studies were carried out to find the optimum physical conditions and which came out to be pH 7 and temperature 30 °C. Amaranth could also be decolorized at concentration 500 mg l(-1). Presence of Zn and Hg ions could strongly slow down the decolorization process, whereas decolorization progressed rapidly in presence of Mn. Decolorization rate was increased with increasing cell mass. Induction in intracellular and extracellular activities of tyrosinase and NADH-DCIP reductase along with intracellular laccase and veratryl alcohol oxidase indicated their co-ordinate action during dye biodegradation. Up-flow bioreactor studies with alginate immobilized cells proved the capability of strain to degrade Amaranth in continuous process at 20 ml h(-1) flow rate. Various analytical studies viz.--HPLC, HPTLC, and FTIR gave the confirmation that decolorization was due to biodegradation. From GC-MS analysis, various metabolites were detected, and possible degradation pathway was predicted. Toxicity studies carried out with Allium cepa L. through the assessment of various antioxidant enzymes viz. sulphur oxide dismutase, guaiacol peroxidase, and catalase along with estimation of lipid peroxidation and protein oxidation levels conclusively demonstrated that oxidative stress was generated by Amaranth.

Efficient microbial conversion of L-tyrosine to L-DOPA by Brevundimonas sp. SGJ.

L-DOPA (3,4-dihydroxyphenyl-L-alanine), the most widely used drug for the treatment of Parkinson's disease, was produced in buffer using biomass of Brevundimonas sp. SGJ. The effects of enhancers, such as carrageenan, diatomaceous earth, and activated charcoal, on the L-DOPA production were evaluated to obtain the maximum yield. The optimal process conditions found were pH 8, 2 g l⁻¹ cell mass, 2 g l⁻¹ L-tyrosine, 0.04 g l⁻¹ CuSO4, 0.02 g l⁻¹ L-ascorbic acid, 0.5 g l⁻¹ carrageenan, and 40 °C temperature. In addition, repeated use of cells resulted in the highest yield of 3.81 g l⁻¹ (95.2%) of L-DOPA with utilization of 4 g l⁻¹ L-tyrosine, and the highest tyrosinase activity (9,201 U mg⁻¹) was observed at 18 h of incubation. Furthermore, the produced L-DOPA was confirmed by high-performance thin-layer chromatography, high-performance liquid chromatography, and gas chromatography-mass spectroscopy. Kinetic studies showed significant values of Y (p/s), Q (s), and q (s) after optimization of the process. Thus, Brevundimonas sp. SGJ could be an eventual new source for large-scale production of L-DOPA.