Comparative biocatalytic degradation of Kraft prehydrolysate phenolic fermentation inhibitors using bacteria-derived laccase

Kraft prehydrolysate contains fermentable sugars and other organic compounds such as furans, phenolic compounds and acids, which are toxic to the fermentation microorganisms. In this work, bacteria-derived laccases were used to degrade key phenolic compounds. Firstly, the potential of degrading the key phenolic compounds in the prehydrolysate was determined. This was followed by tests with synthetic solutions to determine how specific phenolic compounds, vanillin, gallic acid, catechol and syringaldehyde, are degraded individually and in synergy. An evaluation of the simultaneous detoxification and enzymatic hydrolysis of the sugars was performed. The results showed that an enzyme dosage of at least 100 mu L of laccase/g of phenol is required to obtain a significant detoxification of the prehydrolysate. Differences in the degradation of the compounds in single-component solutions and in a mixture were identified. Gallic acid and syringaldehyde are preferentially degraded, followed by vanillin and catechol.