Efficient co-production of xylooligosaccharides and glucose from lignocelluloses by acid/pentanol pretreatment: Synergetic role of lignin removal and inhibitors

Novel ternary acidic deep eutectic solvent with high recyclability aimed at selective fractionation of lignin and fermentable sugars from bamboo

A ternary acidic deep eutectic solvent was synthesized with ethylamine hydrochloride (EH), DL-malic acid (MA) and polyethylene glycol 400 (PEG400) for the pretreatment of bamboo biomass. The EH/MA/PEG400 DES possessed superior biomass pretreatment capability, resulting in the removal of 75.42 % hemicellulose and 85.30 % lignin while retaining the majority of the cellulose (87.53 %) under a relatively high solid/liquid ratio (1:7). Pretreated bamboo biomass obtained a high glucose yield of 87.38 % after 72 h of enzymatic hydrolysis. Furthermore, EH/MA/PEG400 DES exhibited exceptional recyclability, which could afford 79.34 % lignin removal and 85.29 % glucose yield even at the seventh pretreatment cycles without introducing of fresh DES. The analysis on the recovered DES revealed that the accumulation of formic acid generated from carbohydrate degradation during the pretreatment process should account for the excellent recyclability of the EH/MA/PEG400 DES. The findings in this study could offer a sustainable and efficient approach for the lignocellulosic biomass refining.

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.

Enzymatic production of xylooligosaccharide from lignocellulosic and marine biomass: A review of current progress, challenges, and its applications in food sectors

Over the last decade, xylooligosaccharides (XOS) have attracted great attentions because of their unique chemical properties and excellent prebiotic effects. Among the current strategies for XOS production, enzymatic hydrolysis is preferred due to its green and safe process, simplicity in equipment, and high control of the degrees of polymerization. This paper comprehensively summarizes various lignocellulosic biomass and marine biomass employed in enzymatic production of XOS. The importance and advantages of enzyme immobilization in XOS production are also discussed. Many novel immobilization techniques for xylanase are presented. In addition, bioinformatics techniques for the mining and designing of new xylanase are also described. Moreover, XOS has exhibited great potential applications in the food industry as diverse roles, such as a sugar replacer, a fat replacer, and cryoprotectant. This review systematically summarizes the current research progress on the applications of XOS in food sectors, including beverages, bakery products, dairy products, meat products, aquatic products, food packaging film, wall materials, and others. It is anticipated that this paper will act as a reference for the further development and application of XOS in food sectors and other fields.

Novel approach for corn straw biorefineries: Production of xylooligosaccharides, lignin and ethanol by nicotinic acid hydrolysis and pentanol pretreatment

The productive separation and conversion of corn straw offers significant prospects for the economic viability of biorefineries centered on straw resources. In this work, a graded utilization method was proposed to produce xylo-oligosaccharides (XOS), ethanol and lignin from corn straw by nicotinic acid (NA) hydrolysis and water/pentanol pretreatment. A XOS yield of 52.6 % was achieved under optimized conditions of 100 mM NA, 170 °C and 30 min. The solid residue was directly treated with water/pentanol, achieving a lignin removal rate of 79.7 %, and the total XOS yield was improved to 62.6 %. The lignin recovered from pentanol had a high purity of 97.6 %, with high phenolic OH content. Simultaneous saccharification and fermentation of final residue resulted in an ethanol yield of 92.0 %, which yielded 55.3 g/L ethanol. Thus, NA hydrolysis and water/pentanol pretreatment provided an efficient, environmentally friendly approach to fractionate corn straw for the co-production of XOS, ethanol, and lignin.

Advances on Cellulose Manufacture in Biphasic Reaction Media

Cellulose is produced industrially by the kraft and sulfite processes. The evolution of these technologies in biorefineries is driven by the need to obtain greater added value through the efficient use of raw materials and energy. In this field, organosolv technologies (and within them, those using liquid phases made up of water and one partly miscible organic solvent, known as "biphasic fractionation" in reference to the number of liquid phases) represent an alternative that is receiving increasing interest. This study considers basic aspects of the composition of lignocellulosic materials, describes the fundamentals of industrial cellulose pulp production processes, introduces the organosolv methods, and comprehensively reviews published results on organosolv fractionation based on the use of media containing water and an immiscible solvent (1-butanol, 1-pentanol or 2-methyltetrahydrofuran). Special attention is devoted to aspects related to cellulose recovery and fractionation selectivity, measured through the amount and composition of the treated solids.

Bioprocess development for the production of xylooligosaccharide prebiotics from agro-industrial lignocellulosic waste

The development of sustainable biorefineries and bioeconomy has been the mandate of most of the governments with major focus on restricting the climate change concerns and finding new strategies to maintain the global food supply chain. Xylooligosaccharides (XOS) are short-chain oligomers which due to their excellent prebiotic potential in the nutraceutical sector has attracted intense research focus in the recent years. The agro-industrial crop and food waste can be utilized for the production of XOS which are derived from hemicellulose fraction (xylan) of the lignocellulosic materials. The extraction of xylan, is traditionally achieved by acidic and alkaline pretreatments which, however, have limited industrial applications. The inclusion of cutting-edge and environmentally beneficial pretreatment methods and technologies such as deep eutectic solvents and green catalysts are preferred. Moreover, the extraction of xylans from biomass using combinatorial pretreatment approaches may help in economizing the whole bioprocess. The current review outlines the factors involved in the xylan extraction and depolymerization processes from different lignocellulosic biomass and the subsequent enzymatic hydrolysis for XOS production. The different types of oligosaccharides and their prebiotic potential for the growth of healthy gut bacteria have also been explained. The introduction of modern molecular technologies has also made it possible to identify enzymes and microorganisms with the desired characteristics for usage in XOS industrial production processes.

Integrated pretreatment of poplar biomass employing p-toluenesulfonic acid catalyzed liquid hot water and short-time ball milling for complete conversion to xylooligosaccharides, glucose, and native-like lignin

This work aimed to study an integrated pretreatment technology employing p-toluenesulfonic acid (TsOH)-catalyzed liquid hot water (LHW) and short-time ball milling for the complete conversion of poplar biomass to xylooligosaccharides (XOS), glucose, and native-like lignin. The optimized TsOH-catalyzed LHW pretreatment solubilized 98.5% of hemicellulose at 160 °C for 40 min, releasing 49.8% XOS. Moreover, subsequent ball milling (20 min) maximized the enzymatic hydrolysis of cellulose from 65.8% to 96.5%, owing to the reduced particle sizes and cellulose crystallinity index. The combined pretreatment reduced the crystallinity by 70.9% while enlarging the average pore size and pore volume of the substrate by 29.5% and 52.4%, respectively. The residual lignin after enzymatic hydrolysis was rich in β-O-4 linkages (55.7/100 Ar) with a less condensed structure. This lignin exhibited excellent antioxidant activity (RSI of 66.22) and ultraviolet absorbance. Thus, this research suggested a sustainable waste-free biorefinery for the holistic valorization of biomass through two-step biomass fractionation.

Efficient co-production of xylo-oligosaccharides and probiotics from corncob by combined lactic acid pretreatment and two-step enzymatic hydrolysis

Lactic acid (LA) is efficient in xylo-oligosaccharides (XOS) production from poplar. However, the role of LA in XOS production from corncob has not been carefully elucidated, and the co-production of probiotics of Bacillus subtilis from corncob residue has not been reported. In this study, LA pretreatment was combined with enzymatic hydrolysis to produce XOS and monosaccharides from corncob. An XOS yield of 69.9% was obtained from corncob by combining 2% LA pretreatment and xylanase hydrolysis. Yields of 95.6% glucose and 54.0% xylose were obtained from corncob residue via cellulase, and the resulting cellulase hydrolysate was used to culture B. subtilis YS01. The resulting viable count of the strain was 6.4×10⁸ CFU/mL, and the glucose and xylose utilization rates were 99.0% and 89.8%, respectively. This study demonstrates a green, efficient, and mild process for producing XOS and probiotics from corncob by combining LA pretreatment and enzymatic hydrolysis.

Biodegradation of low-density polyethylene plastic waste by a constructed tri-culture yeast consortium from wood-feeding termite: Degradation mechanism and pathway

Polyethylene (PE) is one of the most common synthetic polymers, and PE waste pollution has been an environmental and health concern for decades. Biodegradation is the most eco-friendly and effective approach for plastic waste management. Recently, an emphasis has been placed on novel symbiotic yeasts isolated from termite guts as promising microbiomes for multiple biotechnological applications. This study might be the first to explore the potential of a constructed tri-culture yeast consortium, designated as DYC, isolated from termites for the degradation of low-density polyethylene (LDPE). The yeast consortium DYC stands for the molecularly identified species Sterigmatomyces halophilus, Meyerozyma guilliermondii, and Meyerozyma caribbica. The LDPE-DYC consortium showed a high growth rate on UV-sterilized LDPE as a sole carbon source, resulting in a reduction in tensile strength (TS) of 63.4% and a net LDPE mass reduction of 33.2% compared to the individual yeasts. All yeasts, individually and in consortium, showed a high production rate for LDPE-degrading enzymes. The hypothetical LDPE biodegradation pathway that was proposed revealed the formation of several metabolites, including alkanes, aldehydes, ethanol, and fatty acids. This study emphasizes a novel concept for using LDPE-degrading yeasts from wood-feeding termites for plastic waste biodegradation.

Sustainable lignocellulose fractionation by integrating p-toluenesulfonic acid/pentanol pretreatment with mannitol for efficient production of glucose, native-like lignin, and furfural

A new cutting-edge lignocellulose fractionation technology for the co-production of glucose, native-like lignin, and furfural was introduced using mannitol (MT)-assisted p-toluenesulfonic acid/pentanol pretreatment, as an eco-friendly process. The addition of optimized 5% MT in pretreatment enhanced the delignification rate by 29% and enlarged the surface area and biomass porosity by 1.07-1.80 folds. This increased the glucose yield by 45% (from 65.34 to 94.54%) after enzymatic hydrolysis relative to those without MT. The extracted lignin in the organic phase of pretreatment exhibited β-O-4 bonds (61.54/100 Ar) properties of native cellulosic enzyme lignin. Lignin characterization and molecular docking analyses revealed that the hydroxyl tails of MT were incorporated with lignin and formed etherified lignin, which preserved high lignin integrity. The solubilized hemicellulose (96%) in the liquid phase of pretreatment was converted into furfural with a yield of 83.99%. The MT-assisted pretreatment could contribute to a waste-free biorefinery pathway toward a circular bioeconomy.

Cobalt oxide nanoparticles as a new strategy for enhancing methane production from anaerobic digestion of noxious aquatic weeds

This study investigated the effect of cobalt oxide nanoparticles (Co₃O₄-NPs) supplementation on anaerobic microbial population changes and anaerobic digestion (AD) performance and production. Co₃O₄-NPs (3 mg/L) showed the maximum enhancement of biogas yield over the cow dung (CD) as control and the co-digestion process of CD with water hyacinth (WH) by 58.9 and 27.2 %, respectively. Furthermore, methane (CH₄) yield was enhanced by 89.96 and 43.4 % over CD and co-digestion processes, respectively. Additionally, the microbiological assessment analysis using VIT® gene probe technology showed that Co₃O₄-NPs enhance the viability of total bacterial cells by 9 %. The techno-economic analysis reflects the revenue of this strategy on the highest net energy content of biogas, which was achieved with 3 mg/L Co₃O₄-NPs and was 428.05 kWh with a net profit of 67.66 USD/m³ of the substrate. Therefore, nanoparticle supplementation to the AD process can be considered a promising approach to enhance biogas and CH₄.