Abstract
•Nano-gold tracing technique was utilized to study the adsorption and transmission.•Mediator-involved enzymatic degradation of lignin was studied.•Effects of mediators on the degradation of lignin: veratryl alcohol>ABTS>Mn2+.•A higher lignin degradation ratio was found during solid-state fermentation.
The degradation of lignin waste by ligninolytic enzymes and the effect of mediators on lignin degradation were studied. Moreover, nano-gold tracing technique was innovatively used to study the adsorption and transmission mechanism of ligninolytic enzymes in the process of SSF. The results showed that the effects of three common mediators on the degradation of lignin were in descending order: veratryl alcohol>ABTS>Mn2+, and the optimum dosages were: Mn2+ (20μMg−1), ABTS (0.2μMg−1), veratryl alcohol (4μMg−1). A significantly high degradation ratio of lignin (31.8%) was achieved at the optimum dosages of ligninolytic enzymes and mediators. In addition, laccase, as a typical ligninolytic enzyme, was selected to conjugate to nano-gold for the study of adsorption and transmission mechanism. An obvious decrease of nano-gold-laccase conjugates was observed after 10 days of enzymatic hydrolysis and there were few laccase residues on the surface of straw fibers after 30 days of enzymatic hydrolysis. The present findings will advance the understanding of mediator-involved enzymatic degradation of lignin, as well as the adsorption and transmission mechanism of ligninolytic enzymes in lignin degradation, which could provide useful references for developing waste biotreatment technology.