Optimization of activated carbon detoxification of dilute ammonia pretreated energy cane bagasse enzymatic hydrolysate by response surface methodology

A challenge in syrup production from lignocellulosic biomass is the presence of non-sugar compounds in the hydrolysate, generated during the hydrolytic process, which negatively impact downstream processes. Energy cane bagasse was pretreated with ammonium hydroxide and then hydrolyzed with enzymes Cellic® CTec2 and HTec2. Non-sugar compounds such as formic acid, acetic acid, levulinic acid, furfural, 5-hydroxymethylfurfural (5-HMF), and phenolic compounds were formed during pretreatment and enzymatic hydrolysis. Activated carbon (AC) treatments were carried out to remove these non-sugar compounds while retaining the fermentable sugars, mostly glucose and xylose. Powdered AC and granular AC were compared and parameters including AC dose, hydrolysate pH and contact time were optimized using response surface methodology. Optimum conditions for powdered AC were 9.21% (w/w) dose, at pH 1.96 for 10 min, and for granular AC were 12.64% (w/w) dose, at pH 1.91 for 51.60 min. At these conditions, approximately 40% acetic acid, 75% formic acid and over 90% levulinic acid, HMF, furfurals, and phenolic compounds were removed with minimal fermentable sugar losses. Activated carbon adsorption can significantly reduce the non-sugar compounds present in the hydrolysate with minimal losses of fermentable sugars, which is beneficial in the production of lignocellulosic syrup and value-added products.