Enzymatic extraction of ferulic acid from brewer’s spent grain: Effect of physical pretreatments and optimization using design of experiments

Abstract

Brewers' grains (BSG), the main waste product of the beer industry, are widely available and rich in fiber and bioactive compounds. Ferulic acid (FA) is the main phenolic compound in BSG, it has antioxidant and antibacterial properties that make it a valuable product for cosmetic, food and pharmaceutical industries. Alkaline hydrolysis is the common technology for extracting FA from biomass, this technology needs to be substituted as it is non-selective and requires harsh conditions making purification more complicated and expensive. This research work presents enzymatic hydrolysis as a green alternative for FA extraction. Five commercial enzymes were screened and compared for their hydrolytic efficiency to release FA. Prior to the enzymatic hydrolysis, autoclave was selected as the most effective pretreatment. Depol 740L was selected as the desired enzyme based on its high feruloyl esterase activity (0.4 U/mL). The enzymatic extraction parameters (pH, temperature and enzyme dosage) were optimized using response surface methodology. The highest FA recovery, 1.06 ± 0.01 mg/g dry weight (43.13% in comparison with the alkaline hydrolysis), could be achieved at pH 5.27; temperature 60 °C and 1.72% enzyme. The optimal extraction conditions were found to be sufficient within 22 h, as determined by a kinetic study.