Abstract
Hydroxyl radical ((OH)-O-center dot) is a radical species highly destructive for lignin during solid-state fermentation (SSF) of straw with Phanerochaete chrysosporium (Pc). The production of (OH)-O-center dot at different initial Pb2+ concentrations during SSF of straw with Pc was investigated. The results showed that a modest amount (under 200 mgkg(-1)) of Pb2+ could enhance the production of (OH)-O-center dot, while a higher Pb2+ concentration resulted in inhibition. The content of (OH)-O-center dot reached the peak value at day 12 in the whole tested samples, and the maximal content of (OH)-O-center dot was obtained at initial Pb2+ concentration of 100 mg kg(-1). It was also found that the production of (OH)-O-center dot was connected to enzymatic activity and oxalate content in some degree, in particular, a significant positive correlation was found between oxalate concentration and production of (OH)-O-center dot. We found that low concentration of Pb2+ can promote the degradation of lignin, and the higher initial Pb2+ concentration (400 mg kg(-1)) resulted in inhibition. In addition, it appeared that there was no significant correlation between lignin degradation rate and the production of (OH)-O-center dot when Pb2+ concentration was taken into account. (C) 2014 Elsevier B.V. All rights reserved.