Efficient enzymatic hydrolysis of the bagasse pulp prepared with active oxygen and MgO-based solid alkali

Mild O2-aided alkaline pretreatment effectively improves fractionated efficiency and enzymatic digestibility of Napier grass stem towards a sustainable biorefinery

Napier grass is a promising energy source on account of its strong adaptability and high productivity. Herein, an O₂-aided alkaline pretreatment with mild operating conditions was developed to modify Napier grass stem structure for improving its fractionated efficiency and enzymatic digestibility. Compared with the conventional alkaline pretreatment, it could be proceeded at lower temperature (80 °C) and dilute NaOH solution (1%) to remove over 80% lignin and retain 92% cellulose. The recovered lignin possessed typical structures of native lignin and well-preserved molecular weight, anticipating feasible potential in preparation of biomaterials or aromatic chemicals. Coupled with the enzymatic hydrolysis managements of solid remain and hydrolysate after the pretreatment, the recovery yields of glucose and xylose based on the raw material feeds reached 89.7% and 90.2%, respectively. This contribution demonstrates a highly-reliable strategy to fractionate Napier grass stem for maximizing fermentation sugar production and valorizing lignin toward sustainable biorefinery processes.

Cooking with Active Oxygen and Solid Alkali: A Promising Alternative Approach for Lignocellulosic Biorefineries

Lignocellulosic biomass, a matrix of biopolymers including cellulose, hemicellulose, and lignin, has gathered increasing attention in recent years for the production of chemicals, fuels, and materials through biorefinery processes owing to its renewability and availability. The fractionation of lignocellulose is considered to be the fundamental step to establish an economical and sustainable lignocellulosic biorefinery. In this Minireview, we summarize a newly developed oxygen delignification for lignocellulose fractionation called cooking with active oxygen and solid alkali (CAOSA), which can fractionate lignocellulose into its constituents and maintain its processable form. In the CAOSA approach, environmentally friendly chemicals are applied instead of undesirable chemicals such as strong alkalis and sulfides. Notably, the alkali recovery for this process promises to be relatively simple and does not require causticizing or sintering. These features make the CAOSA process an alternative for both lignocellulose fractionation and biomass pretreatment. The advantages and challenges of CAOSA are also discussed to provide a comprehensive perspective with respect to existing strategies.

Enhanced enzymatic saccharification of sugarcane bagasse pretreated by combining O2 and NaOH

Sugarcane bagasse pretreated by combining O2 and NaOH with different variables was conducted to improve its enzymatic digestibility and sugar recovery, and the results were compared with sole NaOH pretreatment. Lignin removal for O2-NaOH pretreatment was around 10% higher than that for sole NaOH pretreatment under the same conditions, and O2-NaOH pretreatment resulted in higher glucan recovery in the solid remain. Subsequently, O2-NaOH pretreated sugarcane bagasse presented more efficient enzymatic digestibility than sole NaOH pretreatment. Under the moderate pretreatment conditions of combining 1% NaOH and 0.5MPa O2 at 80°C for 120min, a high glucan conversion of 95% was achieved after 48h enzymatic hydrolysis. Coupled with the operations of pretreatment and enzymatic hydrolysis, an admirable total sugar recovery of 89% (glucose recovery of 93% and xylose recovery of 84%) was obtained. The susceptibility of the substrates to enzymatic digestibility was explained by their physical and chemical characteristics.