Glyphosate and aminomethylphosphonic acid degradation in biomixtures based on alfalfa straw, wheat stubble and river waste.

The aim of the work was to evaluate novel biomixtures for their use on biopurification systems (BPS) in Argentina also called biobeds. Glyphosate and aminomethylphosphonic acid (AMPA) degradation was evaluated on biomixtures containing local materials: alfalfa straw (As), wheat stubble (Ws), river waste (Rw) and soil. Glyphosate, AMPA concentrations and biological activity were followed with time. Soil was used as control. Glyphosate initial concentration was 1000 mg kg-1. Glyphosate disappeared almost completely after 63 days in all tested biomixtures. For Ws, WsRw and AsRw glyphosate degradation was around 99% and for As 85%. The biomixture Ws showed the highest glyphosate degradation rate. In all cases AMPA was formed and degraded to concentrations between 60 and 100 mg kg-1. In the control with only soil, glyphosate was degraded 53% and AMPA concentration at the end of the test was 438 mg kg-1. We conclude that alfalfa straw, wheat stubble and river waste are local materials that can be used in the preparation of biomixtures since they showed higher glyphosate degradation capacity and less AMPA accumulation compared to the soil alone. Also, the presence of river waste did enhance the water retention capacity.

Degradation of polycyclic aromatic hydrocarbons by free and nanoclay-immobilized manganese peroxidase from Anthracophyllum discolor.

Manganese peroxidase (MnP) produced by Anthracophyllum discolor, a Chilean white rot fungus, was immobilized on nanoclay obtained from volcanic soil and its ability to degrade polycyclic aromatic hydrocarbons (PAHs) compared with the free enzyme was evaluated. At the same time, nanoclay characterization was performed. Nanoclay characterization by transmission electronic microscopy showed a particle average size smaller than 100 nm. The isoelectric points (IEP) of nanoclay and MnP from A. discolor were 7.0 and 3.7, respectively, as determined by micro electrophoresis migration and preparative isoelectric focusing. Results indicated that 75% of the enzyme was immobilized on the nanoclay through physical adsorption. As compared to the free enzyme, immobilized MnP from A. discolor achieved an improved stability to temperature and pH. The activation energy (Ea) value for immobilized MnP (51.9 kJ mol(-1)) was higher than that of the free MnP (34.4 kJ mol(-1)). The immobilized enzyme was able to degrade pyrene (>86%), anthracene (>65%), alone or in mixture, and to a less extent fluoranthene (<15.2%) and phenanthrene (<8.6%). Compared to free MnP from A. discolor, the enzyme immobilized on nanoclay enhanced the enzymatic transformation of anthracene in soil. Overall results indicate that nanoclay, a carrier of natural origin, is a suitable support material for MnP immobilization. In addition, immobilized MnP shows an increased stability to high temperature, pH and time storage, as well as an enhanced PAHs degradation efficiency in soil. All these characteristics may suggest the possible use of nanoclay-immobilized MnP from A. discolor as a valuable option for in situ bioremediation purposes.