Improving bagasse degradability and enzymatic activity of a Cd-polluted soil by inoculation with Phanerochaete chrysosporium

Abstract

Phanerochaete chrysosporium was used to investigate the degradation of bagasse and the activities of cellulase and β-glucosidase in a Cadium (Cd) contaminated soil. The soil was treated with sugarcane bagasse (5%) and the experiment was performed as a repeated measures design with three factors, a Cd treatment (0, 20 and 40mg Cd kg−1), addition of fungi (inoculation with P chrysosporium and uninoculated) and experimental duration (sampling at days 1, 20, 50 and 90) with three replicates. At the end of the experiment, the concentration of Lignocellulosic compounds, carbon fractions, Cd availability, biological properties and β-glucosidase and cellulase activity were measured. A higher Cd bioavailability (40mg Cd kg−1 compared to 20mg Cd kg−1 with a control) resulted in lower enzyme activity, lower carbon fractions (cold and hot water extractable and peroxidizable carbon), lower soil biological properties (soil respiration and soil microbial carbon) and lower degradation of bagasse (higher amount of cellulose, hemicellulose and lignin). Fungal inoculation and incubation time resulted in these properties being modified to some extent. Lignocellulosic compounds decreased during the incubation and in fungus-inoculated treatments, indicating bagasse degradation. The activity of enzymes was higher in fungus-inoculated treatments (7.12μg PNG g−1 soil−1 h−1 for β-glucosidase and 0.17μmol min−1 for cellulase) than in uninoculated treatments (6.39μg PNG g−1 soil−1 h−1 for β-glucosidase and 0.13μmol min−1 for cellulase). P chrysosporium effectively degraded sugarcane bagasse, even in Cd polluted soil. However, a decrease in Cd availability occurred from day 1 to day 90, but the activity of the different enzymes did not increase as much as might have been expected. For each Cd level, the concentration of lignocellulosic compounds probably had more of an effect on enzyme activity than the bioavailability of Cd.