Nowadays, thermochemical modification has been mainly studied, focusing on production of phenolic compounds from lignin. However, thermochemical modification leads to also polymerization of lignin because of harsh conditions such as high temperature and pressure. Accordingly, new approach is necessary for lucrative lignin application.
This study tried to introduce two-step modification process, thermochemical and biological process for depolymerization of lignin. At first, ethanol organosolv lignin (EOL) separated from yellow poplar was treated under the supercritical condition, 350°Cfor 40 min with ethanol. Characteristics of lignin oil produced from EOL were followings: weight- average molecular weight (Mw) was 1,000, and it contained 55.93 mg/g of EOL of monomers. And then, biological treatment by Abortiporus biennis was carried out with addition of reducing agent and enzyme mediator.
A. biennis polymerized lignin oil with increase of molecular weight. Mw of lignin oil by fungus was 1,162 on incubation day 7, and monomer content was decreased. According to these results, we performed experiments with addition of reducing agent, ascorbic acid. Addition of ascorbic acid impacted on decline of molecular weight (Mw 882) and increase of monomer content, which means that ascorbic acid inhibited polymerization of lignin oil. Additionally, the effect of laccase-mediator treatment on properties of lignin oil is scheduled to investigate.
Consequently, this study is expected to produce depolymerized lignin-derived compounds by A. biennis.