Combined effect of enzyme inducers and nitrate on selective lignin degradation in wheat straw by Ganoderma lobatum

• Published in: Environmental science and pollution research international 2017-09, Vol.24 (27), p.21984-21996
• Main Authors: Hermosilla, Edward, Schalchli, Heidi, Mutis, Ana, Diez, María Cristina
• Format: Article
• Language: English
• Subjects: Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Biodegradation; Biodegradation, Environmental; Cellulose; Confocal microscopy; Degradation; Design optimization; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; Enzyme Induction; Enzymes; Fungi; Ganoderma - enzymology; Ganoderma - metabolism; Hemicellulose; Iron; Lignin; Lignin - metabolism; Ligninolytic enzymes; Lignocellulose; Manganese; Nitrates; Nitrates - metabolism; Organic compounds; Research Article; Rot; Scanning microscopy; Selectivity; Straw; Triticum; Waste Water Technology; Water Management; Water Pollution Control; Wheat; Wheat straw
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-017-9841-4

Lignin is one of the main barriers to obtaining added-value products from cellulosic fraction of lignocellulosic biomass due to its random aromatic structure and strong association with cellulose and hemicellulose. Inorganic and organic compounds have been used as enzyme inducers to increase the ligninolytic potential of white-rot fungi, without considering their effect on the selectivity of degradation. In this study, the selective lignin degradation in wheat straw by Ganoderma lobatum was optimized using a central composite design to evaluate the combined effect of Fe 2+ and Mn 2+ as inducers of ligninolytic enzymes and NO 3 − as an additional nitrogen source. Selective lignin degradation was promoted to maximize lignin degradation and minimize weight losses. The optimal conditions were 0.18 M NO 3 − , 0.73 mM Fe 2+ , and 1 mM Mn 2+ , which resulted in 50.0% lignin degradation and 18.5% weight loss after 40 days of fungal treatment. A decrease in absorbance at 1505 and 900 cm −1 in fungal-treated samples was observed in the FTIR spectra, indicating lignin and cellulose degradation in fungal-treated wheat straw, respectively. The main ligninolytic enzymes detected during lignin degradation were manganese-dependent and manganese-independent peroxidases. Additionally, confocal laser scanning microscopy revealed that lignin degradation in wheat straw by G. lobatum resulted in higher cellulose accessibility. We concluded that the addition of enzyme inducers and NO 3 − promotes selective lignin degradation in wheat straw by G. lobatum .