Enhanced hydrolysis of Macrocystis pyrifera by integrated hydroxyl radicals and hot water pretreatment

• Fenton reaction first materialized in the biomass pretreatment.
• The carbohydrate recovery of macroalgae with the pretreatment approach attained 100%.
• The glucose yield of M. pyrifera could reach 92.1%.
• This new pretreatment requires low chemical solvents and energy consumption.
• No inhibitors were formed after the application of the new pretreatment method.

Integrated hydroxyl radicals and hot water pretreatment (IHRHW) was employed in the bioconversion of the brown macroalgae Macrocystis pyrifera (M. pyrifera) in this study. The optimum experimental pretreatment condition (100 °C, 30 min, 11.9 mM FeSO4) and the predicted optimum pretreatment condition (113.95 °C, 29.1 min, 12.75 mM FeSO4) were identified using a central composite design method. All glucan and xylan were recovered as monosaccharides or polysaccharides without a fermentation inhibitor (e.g., hydroxymethyl furfural and furfural). The IHRHW-treated macroalgae digestibility reached 88.1% under the optimum experimental condition, whereas that under the predicted optimum condition reached 92.1%. The value was approximately threefold higher than those obtained with untreated M. pyrifera. Carbohydrate recovery and enzymatic hydrolysis can be significantly enhanced by the new economic hydroxyl radicals and hot water pretreatment.