Enhanced removal of dibutyl phthalate in a laccase-mediator system: Optimized process parameters, kinetics, and environmental impact.

The persistence and recalcitrance of endocrine-disrupting chemicals (EDCs) in the environment have raised momentous concerns due to their carcinogenic, teratogenic, genotoxic, and cytotoxic effects on humans, animals, and plants. Unarguably, dibutyl phthalate (DBP) is one of the most ubiquitous EDCs because of its bioavailability in water, soil, and atmosphere. This study aims to investigate the efficiency of Agaricus bisporus laccase in the degradation of dibutyl phthalate (DBP) in laccase-mediator system. Here, enhanced removal efficiency was recorded during DBP degradation in laccase-mediator systems than in reaction medium containing laccase only. About 98.85% of 30 mg L-1 DBP was efficiently removed in a medium containing 1.3 U mL-1, 0.045 mM Syringaldehyde (SYR) at incubation temperature 30 aC and pH 5 within 24 h. This finding was further corroborated by the synergistic interplay of the optimal parameters in the laccase-SYR system done using response surface methodology (Box-Behnken Design). Furthermore, the addition of 1.5 mM of metal ions in the laccase-SYR system further promoted the enhanced removal of DBP in the following order: Cr3+> Pb2+> Ca2+> Al3+>Zn2+ > Cu2+. A significant decrease in DBP degradation was observed at higher concentrations of metal ions above 1.5 mM due to the inhibition of laccase active sites. The coefficient of correlation (R2 = 0.9885) recorded in the Lineweaver bulk plot affirmed that the removal efficiencies are highly dependent on DBP concentration in the laccase-SYR system. The Gas-Chromatography Mass Spectrometry (GC-MS) analyses affirmed that the ortho-cleavage due to hydrolysis of DBP in the reaction system led to the formation of two metabolic degradation products (MBP and PA). The phytotoxicity assessment affirmed the detoxified status of DBP after treatment with significant improvement (90 and 91%) in the growth of Lens culinaris and Sorghum bicolor. This is the first report on DBP degradation in the laccase-SYR reaction system, underscoring the unique, eco-friendly, economical, and promising alternative to known conventional methods.

Novel laccase from Xylaria polymorpha and its efficiency in the biotransformation of pharmaceuticals: Optimization of operational conditions, comparative effect of redox-mediators and toxicity studies.

The promising potentials of biocatalytic treatment processes in the removal of micropollutants whilst eliminating health and environmental hazards have attracted great attention in recent years. This current work investigated the biotransformation efficiency of a novel laccase from Xylaria polymorpha (XPL) in comparison with commercial laccases from Trametes versicolor (TVL) and Aspergillus sp. (ASL). XPL exhibited better oxidation performance (95.7%) on AMX than TVL (92.8%) and ASL (90.5%). Optimization of operational conditions revealed that AMX was best oxidized at pH 5, temperature (30 °C), and concentration (1.0 mg L-1). The investigation carried out to determine the effect of redox mediators revealed violuric acid (VLA) as the best redox mediator. The laccase stability experiments elucidated that the oxidation of AMX is time and mediator concentration dependent with ABTS exhibiting highest deactivation of XPL active sites. Two metabolic products; amoxicillin penilloic acid and 5-hydroxy-6-(4-hydroxyphenyl)- 3-(1,3-thiazolidin-2-yl)piperazin-2-one of AMX were obtained through Liquid Chromatography-Mass Spectrometry (LC-MS) analyses. The toxicity assessments carried out after oxidation of AMX by XPL showed 94% and 97% reduced toxicity on Artemia salina and Aliivibrio fischeri respectively. The study further underscored the efficiency of biocatalytic-mediator technology in the transformation of complex micropollutants into less toxic substances in an eco-friendly way.

Impacts of rice-husk biochar on soil microbial biomass and agronomic performances of tomato (Solanum lycopersicum L.).

Tomato is beneficial to human health because it contains valuable vitamins such as vitamins A, C and several minerals. However, to meet up with the demands of the ever increasing population, there is need to improve tomato production. This research, thus, investigated the impact of rice-husk biochar on the agronomic performances of tomato plant and microbial biomass of carbon, nitrogen and phosphorus in different tomato growth stages. The rice husk biochar pyrolyzed at 350 °C was amended with soil at four different application rates: 0, 2.5, 5.0 and 7.5 t/ha. Physicochemical property of soil was conducted using Mid Infrared Reflectance Spectroscopy method. Impact of biochar on Microbial Biomass Carbon, Microbial Biomass Nitrogen and Microbial Biomass Phosphorous was conducted using fumigation extraction method and monitored at three functional stages. Biochar application appreciably increase the soil physicochemical properties such as pH, Ca, Na, H+, S, P, B, C, Zn and cation exchangeable capacity in comparison with the control. Biochar amended soil significantly enhanced tomato height, stem girth, leaf area, flowers, fruit yields and weight. Although, B3 recorded the lowest leaf area, it possessed the highest number of fruits and fruit weight of 3 and 40%, respectively. The ratio of Microbial biomass C:N:P for biochar amended soil at 7.5 t/ha (B3) was 302.30:18.81:11.75 µg/g, compared to control, which was 242.12:18.30:11.49 µg/g. This study revealed that biochar amendments significantly (p < 0.05) increased the yields and microbial biomass of tomato plants. Conclusively, the application of rice-husk biochar (7.5 t/ha) to soil is considered as a suitable approach to improve tomato growth and yield.