New assay for lignin depolymerization based on lignin films

We have developed a new methodology for detecting and quantifying lignin depolymerization.  The assay is based on casting films of lignin onto silicon wafers and measuring the loss of mass upon treatment through the decrease in thickness.  A silicone mold in the form of a standard 96-well plate is pressed against the silicon wafer to create a highly multiplexed format.  The assay is highly sensitive, quantitative, and compatible with standard 96-well plate robotic fluid handling systems.  This assay enables rapid assessment of the ligninolytic potential of a large number of catalytic chemistries, ligninolytic enzymes, and reaction conditions, and also rapid identification of ligninolytic organisms and microbial communities.  The multiplexed device was constructed and refined through several stages.   To demonstrate this assay, various trials were performed involving the Fenton reaction.  The Fenton reaction, reaction of hydrogen peroxide and ferrous salt, is used to treat industrial waste and organic contaminants in groundwater and has been employed in biomass pretreatment strategies.  The trials demonstrated that up to 80 different reaction conditions can be assayed simultaneously.  The results showed that the mass of soluble fragments released from the lignin film went through a maximum as a function of the concentration of each reactant.   This is likely due to competing factors in the physical chemistry of the oxidative reactions that lead to a competition between depolymerization and repolymerization.   The concentration of ferrous salt that yielded the maximum release of soluble fragments increased with increasing concentration of hydrogen peroxide.