Pretreatment of sugarcane bagasse with acid catalyzed ethylene glycol-water to improve the cellulose enzymatic conversion

Low dosage ionic liquid-driven mild and selective lignocellulosic deconstruction of corn stover using biphasic co-solvent systems

Ionic liquids (ILs) are highly effective in lignocellulose pretreatment due to their excellent solvation properties. However, the single-phase nature of conventional IL pretreatment not only causes component mixing, complicating separation and utilization, but also limits large-scale application due to the high cost. To address these challenges, this study developed a biphasic pretreatment system combining the protic IL [BHEM]mesy with aqueous pentanol, aiming to efficiently fractionate corn stover under mild conditions. The effects of varying conditions on corn stover composition were systematically investigated. The optimal pretreatment conditions (10 % IL, 60 % pentanol, 140 °C, 60 min) resulted in 91.6 % cellulose content in solid residue with 89.3 % hemicellulose and 82.9 % lignin removal. Enzymatic hydrolysis of pretreated residues was significantly better than residues pretreated with IL or pentanol alone. In the biphasic system, 70.8 % of the available xylose dissolved into the aqueous phase, while the organic phase facilitated the recovery of 82.9 % lignin with high phenolic hydroxyl. Quantum chemical calculations revealed that the IL-pentanol co-solvent system reduces IL consumption while exhibiting higher reactivity than either component alone. This study demonstrates a cost-effective and efficient approach for lignocellulose pretreatment, offering significant potential for high-value utilization of its components.

Lignin from Plant-Based Agro-Industrial Biowastes: From Extraction to Sustainable Applications

Lignin, the most abundant aromatic polymer in nature, plays a critical role in lignocellulosic biomasses by providing structural support. However, its presence complicates the industrial exploitation of these materials for biofuels, paper production and other high-value compounds. Annually, the industrial extraction of lignin reaches an estimated 225 million tons, yet only a fraction is recovered for reuse, with most incinerated as low-value fuel. The growing interest in lignin potential has sparked research into sustainable recovery methods from lignocellulosic agro-industrial wastes. This review examines the chemical, physical and physicochemical processes for isolating lignin, focusing on innovative, sustainable technologies that align with the principles of a circular economy. Key challenges include lignin structural complexity and heterogeneity, which hinder its efficient extraction and application. Nonetheless, its properties such as high thermal stability, biodegradability and abundant carbon content place lignin as a promising material for diverse industrial applications, including chemical synthesis and energy generation. A structured analysis of advancements in lignin extraction, characterization and valorization offers insights into transforming this undervalued by-product into a vital resource, reducing reliance on non-renewable materials while addressing environmental sustainability.

The co-production of xylose, fermentable glucose and β-O-4 linkage-rich lignin through efficiently dismantling sugarcane bagasse

As an "upstream" process in biorefinery, biomass dismantling can dismantle the natural stable structure of lignocellulosic biomass and separate its three major components. To increase the value of the entire biomass by fully utilizing the three main components (cellulose, lignin, and hemicellulose), this study proposes a two-step decomposition system combining formic acid (FA) pretreatment and ethylene glycol-NaOH (EGA) dismantling, aiming to effectively convert sugarcane bagasse into xylose, fermentable glucose, and high-value lignin. In the first step, FA pretreatment removed 79.85 % of hemicellulose at 140 °C for 90 min with 3 % FA. Based on the first step, further combination of EGA dismantling can achieve a hemicellulose removal rate of 92.05 % and a lignin removal rate of 95.90 %. In addition, the solid residue was hydrolyzed by enzymes, and the glucose conversion rate was close to 83.29 % when the cellulase dosage was 10 FPU/g. In addition, the lignin recovered by this system retained 83.62 % of the natural β-O-4 structure, which has the potential to catalyze the formation of aromatic monomers. In summary, this gentle two-step system simultaneously improves the efficiency of lignocellulose decomposition and produces different value-added products, demonstrating the potential for industrial-scale production.

Mild γ-Butyrolactone/Water Pretreatment for Highly Efficient Sugar Production from Corn Stover

In this study, γ-butyrolactone/water (GBL/H2O) was explored as a mild, efficient, and cost-effective binary solvent pretreatment to enhance hydrolyzability of corn stover (CS). Key pretreatment parameters-reaction time, temperature, and H2SO4 concentration-were systematically investigated for their effects on the physicochemical properties of CS. Specifically, increased temperature and acid concentration significantly decreased cellulose crystallinity (from 1.39 for untreated CS to 1.04 for CS pretreated by GBL/H2O with 100 mM H2SO4 at 120 °C for 1 h) and promoted lignin removal (47.3% for CS pretreated by GBL/H2O with 150 mM H2SO4 at 120 °C for 1 h). Acknowledging the cellulase's limited hydrolysis efficiency, a dual-enzyme scheme using a low cellulase dosage (10 FPU/g) supplemented with β-glucosidase or xylanase was tested, enhancing hydrolysis of CS pretreated under low temperature-long duration and high temperature-short duration conditions, respectively. Optimum sugar release was obtained from CS pretreated with GBL/H2O and 150 mM H2SO4 at 120 °C for 1 h, achieving 98% glucan and 82.3% xylan conversion, compared with 53.9% and 17% of glucan and xylan conversion from untreated CS. GBL/H2O pretreatment outperformed other binary systems in literature, achieving the highest sugar conversions with lower enzyme loading. These results highlight the potential of GBL/H2O pretreatment for efficient biomass conversion, contributing to the goals of the green economy.

Direct and efficient conversion of cellulose to levulinic acid catalyzed by carbon foam-supported heteropolyacid with Brønsted-Lewis dual-acidic sites

This study aimed to produce bio-based levulinic acid (LA) via direct and efficient conversion of cellulose catalyzed by a sustainable solid acid. A carbon foam (CF)-supported aluminotungstic acid (HAlW/CF) catalyst with Brønsted-Lewis dual-acidic sites was creatively engineered by a hydrothermal impregnation method. The activity of the HAlW/CF catalyst was determined via the hydrolysis and conversion of cellulose to prepare LA in aqueous system. The cooperative effect of Brønsted and Lewis acids in HAlW/CF resulted in high cellulose conversion (89.4%) and LA yield (60.9%) at 180 °C for 4 h, which were greater than the combined catalytic efficiencies of single HAlW and CF under the same conditions. The HAlW/CF catalyst in block form exhibited superior catalytic activity, facile separation from reaction system, and favorable reusability. This work offers novel perspectives for the development of recyclable dual-acidic catalysts to achieve one-pot catalytic conversion of biomass to value-added chemicals.

Development of a Strategy for L-Lactic Acid Production by Rhizopus oryzae Using Zizania latifolia Waste and Cane Molasses as Carbon Sources

As a biodegradable and renewable material, polylactic acid is considered a major environmentally friendly alternative to petrochemical plastics. Microbial fermentation is the traditional method for lactic acid production, but it is still too expensive to compete with the petrochemical industry. Agro-industrial wastes are generated from the food and agricultural industries and agricultural practices. The utilization of agro-industrial wastes is an important way to reduce costs, save energy and achieve sustainable development. The present study aimed to develop a method for the valorization of Zizania latifolia waste and cane molasses as carbon sources for L-lactic acid fermentation using Rhizopus oryzae LA-UN-1. The results showed that xylose derived from the acid hydrolysis of Z. latifolia waste was beneficial for cell growth, while glucose from the acid hydrolysis of Z. latifolia waste and mixed sugars (glucose and fructose) from the acid hydrolysis of cane molasses were suitable for the accumulation of lactic acid. Thus, a three-stage carbon source utilization strategy was developed, which markedly improved lactic acid production and productivity, respectively reaching 129.47 g/L and 1.51 g/L·h after 86 h of fermentation. This work demonstrates that inexpensive Z. latifolia waste and cane molasses can be suitable carbon sources for lactic acid production, offering an efficient utilization strategy for agro-industrial wastes.

Significantly enhanced enzymatic hydrolysis of waste rice hull through a novel surfactant-based deep eutectic solvent pretreatment

The potential of green solvents, specifically deep eutectic solvents (DESs), has piqued the interest of researchers in the field of lignocellulose pretreatment. To enhance the enzymatic digestion efficiency of waste rice hull (RCH), an effective pretreatment approach was developed using the DES [AA][CATB], which was made with acetic acid (AA) and cetyltrimethylammonium bromide (CTAB). The results showed that [AA][CATB] improved enzymatic saccharification by 3.7 times compared to raw RCH and efficiently eliminated lignin (38.7%) and removed xylan (42.9%). The improvement in enzymatic hydrolysis efficiency was then interpreted by a series of characterizations that showed a great morphological changed RCH with an obvious accessibility increase and a lignin surface area and hydrophobicity reduction. This work demonstrates that functional, and easily recoverable DESs have potential for improving the efficiency of lignocellulose pretreatment in biorefineries, providing a promising approach for developing green solvents and achieving more sustainable and efficient biorefinery processes.

Advances in organosolv modified components occurring during the organosolv pretreatment of lignocellulosic biomass

The valorization of organosolv pretreatment (OP) is a required approach to the industrialization of the current enzyme-mediated lignocellulosic biorefinery. Recent literature has demonstrated that the solvolysis happening in the OP can modify the soluble components into value-added active compounds, namely organosolv modified lignin (OML) and organosolv modified sugars (OMSs), in addition to protecting them against excessive degradation. Among them, the OML is coincidental with the "lignin-first" strategy that should render a highly reactive lignin enriched with β-O-4 linkages and less condensed structure by organosolv grafting, which is desirable for the transformation into phenolic compounds. The OMSs are valuable glycosidic compounds mainly synthesized by trans-glycosylation, which can find potential applications in cosmetics, foods, and healthcare. Therefore, a state-of-the-art OP holds a big promise of lowering the process cost by the valorization of these active compounds. Recent advances in organosolv modified components are reviewed, and perspectives are made for addressing future challenges.