Hydrothermal reaction of sulfuric acid lignin generated as a by-product during bioethanol production using lignocellulosic materials to convert bioactive agents

To utilize the by-product lignin (SAL) that is generated by bioethanol production systems that use lignocellulosic materials with a sulfuric acid catalyst, the antioxidant activity, reducing power, and acetylcholinesterase inhibitory activity of SAL were investigated. Hydrothermal treatment effectively increased the total phenolic content (TPC) and had positive effects on the antioxidant activity and reducing power. By using model compounds, the reaction mechanism of the increase in TPC by hydrothermal treatment was determined. The antioxidant activity, reducing power, and acetylcholinesterase inhibitory activity of hydrothermalized SAL were insensitive to the methoxy group content, molecular weight, and differences in nucleus species (such as guaiacyl or syringyl). This suggests that the species of lignocellusic materials have little relationship to the potential utilization of SAL as a bioactive agent.

► The by-product lignin was converted to bioactive agents by hydrothermal reaction.
► The reaction mechanism was investigated by using model compounds.
► Many types of lignocellulosic materials can be used for the conversion reaction.