Effect of Pb2+ on the production of hydroxyl radical during solid-state fermentation of straw with Phanerochaete chrysosporium

•Low concentration of Pb2+ could enhance the production of OH.•OH production declined when the initial Pb2+ concentration reached 400 mg kg−1.•A remarkable correlation was found between OH content and oxalate concentration.•No obvious relationship was found between OH content and lignin degradation rate.

Hydroxyl radical (OH) is a radical species highly destructive for lignin during solid-state fermentation (SSF) of straw with Phanerochaete chrysosporium (Pc). The production of OH at different initial Pb2+ concentrations during SSF of straw with Pc was investigated. The results showed that a modest amount (under 200 mg kg−1) of Pb2+ could enhance the production of OH, while a higher Pb2+ concentration resulted in inhibition. The content of OH reached the peak value at day 12 in the whole tested samples, and the maximal content of OH was obtained at initial Pb2+ concentration of 100 mg kg−1. It was also found that the production of OH 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.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 when Pb2+ concentration was taken into account.