Effect of Soluble Phenolic Compounds From Hydrothermally Pretreated Wheat Straw on Cellulose Degrading Enzymes

Background: Hydrothermal methods are commonly applied in pretreatment of lignocellulose for enhanced enzymatic hydrolysis and further conversion to biofuels and chemicals. The pretreatment partially disassemble and solubilize cell wall polymers. Besides mono- and oligosaccharides, the soluble degradation products include various phenolic compounds, which may affect the efficiency of enzymatic hydrolysis. Results: The phenolic compounds were isolated from pretreatment liquor and their effects on cellulolytic enzymes were investigated. The major enzymes in crystalline cellulose degradation, cellobiohydrolases, were inhibited by the oligophenolics and phenolic-carbohydrate conjugates the latter of which could be mitigated by other enzymes, i.e. xylanases and endoglucanases. Hydrolytic activity of a commercial enzyme cocktail containing lytic polysaccharide monooxygenase (LPMO) was enhanced in presence of low concentrations of phenolics.Conclusions: The effects of the pretreatment liquor phenolics is dependent on enzyme concentration and type of the phenolic compounds. For optimized performance, the pretreatment conditions and enzyme cocktail composition should be designed to promote oxidative activities for enhanced hydrolysis, degradation of the oligosaccharides linked to phenolics and resistance to oligophenolic compounds.