Molecular Characterization of Trichoderma asperellum and Lignocellulolytic Activity on Barley Straw Treated with Silver Nanoparticles

Abstract

Silver nanoparticles (AgNPs) have been applied as an antifungal agent, which results in AgNPs contamination of agricultural waste that interferes with the lignocellulosic enzymes produced by fungi. Therefore, this study examined the production of carboxymethylcellulase (CMCase) and manganese-dependent lignin peroxidase (MnPase), using barley straw treated with AgNPs. Trichoderma asperellum growth was not inhibited at 25 ppm AgNPs, while negligible growth inhibition was observed at 50 ppm AgNPs, which was not observed with Aspergillus terreus and Curvularia lunata. T. asperellum was the highest producer of CMCase and MnPase using barley straw with or without 25 ppm AgNPs versus A. terreus or C. lunata. AgNPs addition to barley straw before T. asperellum inoculation played a role in repressing enzyme activities (CMCase 156.33 U/mL and MnPase 1.28 U/mL); however, addition of AgNPs (50 ppm) after 10 days of incubation showed the highest activity (CMCase 160.67 and 1.35 U/mL MnPase). Optimum temperature for enzyme production by T. asperellum using untreated and treated barley straw was 35 °C and 30 °C, respectively. Enzyme activities increased with increasing polyoxyethylenesorbitan monooleate surfactant concentrations up to 0.25 mL/g substrate without AgNPs, whereas the activity decreased with AgNPs (25 ppm). The exception to this observed trend was at low concentrations of the surfactant (0.10 mL/g substrate).