Sequential acid-/alkali-pretreatment of empty palm fruit bunch fiber

Pretreatment processes are key technologies for generating fermentable sugars based on lignocellulosic biomass. In this study, we developed a novel method for empty palm fruit bunch fiber (EPFBF) using sequential pretreatment with dilute acid and then alkali. Dilute sulfuric acid was used in the first step, which removed 90% of the hemicellulose and 32% of the lignin, but left most of the cellulose under the optimum pretreatment condition. Sodium hydroxide was then applied in the second step, which extracted lignin effectively with a 70% delignification yield, partially disrupting the ordered fibrils of the EPFBF and thus enhancing the enzyme digestibility of the cellulose. The sequentially pretreated biomass consisted of 82% cellulose, less than 1% hemicellulose, and 30% lignin content afterward. The pretreated biomasses morphologically revealed rough, porous, and irregularly ordered surfaces for enhancing enzyme digestibility. These results indicate that the sequentially acid/alkali-pretreated EPFBF could be broadly useful as a novel biomass.

► The sequential acid/alkali pretreatment of EPFBF was effective in removing hemicellulose and lignin. ► This pretreatment reduced the size of fibers and the strength of interactions with fibrils physically. ► It also enhanced enzyme digestibility. ► This novel pretreatment could produce a biomass of high cellulose content. ► The procedure fractionated xylose from hemicellulose and lignin via a sequentially pretreatment.