Enhanced Lignin Degradation in Tobacco Stalk Composting with Inoculation of White-Rot Fungi Trametes hirsuta and Pleurotus ostreatus

Abstract

Tobacco stalk contained large amount of lignin, which is resistant to microbial degradation and limit the composting efficiency during composting. The purpose of this study is to enhance the lignin degradation efficiency, and consequently improve the composting efficiency and product quality. Lignin degrading microorganisms (LDMs) were screened and inoculated to tobacco stalk compost, lignin degradation enzyme activities and lignin degradation rate were measured to evaluate the lignin degradation efficiency, other physico-chemical characters were determined as well to evaluate the composting efficiency and product quality. Two white-rot fungi Trametes hirsuta S13 and Pleurotus ostreatus S18 were screened as LDM according to their high lignin degradation efficiency. After inoculation, lignin peroxidase, manganese peroxidase and laccase were raised from (U g−1) 105.9, 372.9 and 460.68 to 374.7, 1095.6 and 1420.8, respectively. Consequently, lignin degradation rate increased nearly 2-fold (from 23.7 to 41.1%). In addition, organic matter degradation rate was increased from 26.5 to 31.2% with the addition of fungal inoculants. Degree of polymerization, humification index and germination index were also elevated, from 2.0, 17.8% and 108.3% to 3.5, 24.2% and 123.8%, respectively. In this study, T. hirsuta S13 and P. ostreatus S18 were used as LDM and inoculated to tobacco stalk composting. After inoculation, the lignin degradation rate was increased, with the composting efficiency and the quality of composting product was improved as well.