High yield biorefinery products from sugarcane bagasse: Prebiotic xylooligosaccharides, cellulosic ethanol, cellulose nanofibrils and lignin nanoparticles

Xylooligosaccharide Production From Lignocellulosic Biomass and Their Health Benefits as Prebiotics

Lignocellulosic biomass (LCB) comprising of wheat bran, coconut husk, rice husk, cereals straw, and other hardwood and softwoods is a good source for the production of xylooligosaccharides (XOS) (prebiotic). XOS produced are nondigestible carbohydrates being stable under stomach pH and digestive enzymes so they can be easily delivered to the intestine in native form, thus stimulating the growth of probiotics. Here we review about the raw material, production, purification, and application of XOS with health benefits. Importance of XOS being valuable food ingredient is increasing as they perform a variety of functions, including reduction in cholesterol levels, gastrointestinal health maintenance, anticancer and antioxidant properties, and modulation of immune system. We also discuss the different characterization methods which are necessary to determine the degree of polymerization (DP) of XOS. Low DP (xylobiose and xylotriose) is usually preferred for the application of XOS in various sectors. This review emphasizes the growing significance of XOS as a prebiotic, serving as nourishment for probiotics.

One pot green process for facile fractionation of sorghum biomass to lignin, cellulose and hemicellulose nanoparticles using deep eutectic solvent

Complete valorization of lignocellulosic biomass is crucial for bio-based biorefineries to fulfil the circular bioeconomy concept. However, the existence of lignin carbohydrate complexes (LCC) in biomass hinders the simultaneous fractionation of biomass components, such as lignin, hemicellulose and cellulose, for subsequent biorefining processes. This study explores for the first time a novel approach tailored for the deconstruction of sorghum biomass components through efficient breakdown of LCC. Selective targeting of the major LCC linkages binding xylan and lignin was performed using an ultrasound-assisted deep eutectic solvent under mild treatment conditions. This process yielded a maximum cellulose content of 98.3 %, hemicellulose content of 95.2 %, and lignin content of 94.6 %, with the highest purities of 99.43 %, 96.71 %, and 98.12 %, respectively. FTIR, 2D-HSQC NMR and XRD analyses confirmed that most of the structural properties of lignin, hemicellulose, cellulose are retained. The lignocellulosic components were successfully valorised to cellulose, hemicellulose, and lignin nanoparticles with mean sizes of 64.5 ± 6 nm, 72.8 ± 4 nm and 57.2 ± 8 nm respectively, with good thermal stability. The proposed green process enables the complete utilization of agro-residue feedstock for the preparation of biomass-derived nanoparticles, thereby accelerating the economic and industrial prospects of bio-based biorefineries.

Enzymatic approaches for diversifying bioproducts from cellulosic biomass

Cellulosic biomass is the most abundantly available natural carbon-based renewable resource on Earth. Its widespread availability, combined with rising awareness, evolving policies, and changing regulations supporting sustainable practices, has propelled its role as a crucial renewable feedstock to meet the escalating demand for eco-friendly and renewable materials, chemicals, and fuels. Initially, biorefinery models using cellulosic biomass had focused on single-product platform, primarily monomeric sugars for biofuel. However, since the launch of the first pioneering cellulosic plants in 2014, these models have undergone significant revisions to adapt their biomass upgrading strategy. These changes aim to diversify the bioproduct portfolio and improve the revenue streams of cellulosic biomass biorefineries. Within this area of research and development, enzyme-based technologies can play a significant role by contributing to eco-design in producing and creating innovative bioproducts. This Feature Article highlights our strategies and recent progress in utilizing the biological diversity and inherent selectivity of enzymes to develop and continuously optimize sustainable enzyme-based technologies with distinct application approaches. We have advanced technologies for standalone platforms, which produce various forms of cellulose nanomaterials engineered with customized and enhanced properties and high yields. Additionally, we have tailored technologies for integration within a biorefinery concept. This biorefinery approach prioritizes designing tailored processes to establish bionanomaterials, such as cellulose and lignin nanoparticles, and bioactive molecules as part of a new multi-bioproduct platform for cellulosic biomass biorefineries. These innovations expand the range of bioproducts that can be produced from cellulosic biomass, transcending the conventional focus on monomeric sugars for biofuel production to include biomaterials biorefinery. This shift thereby contributes to strengthening the Bioeconomy strategy and supporting the achievement of several Sustainable Development Goals (SDGs) of the 2030 Agenda for Sustainable Development.

Oxidation of p-toluenesulfonic acid fractionated hybrid Pennisetum by different methods for carboxylated nanocellulose preparation: The evaluation of efficiency and sustainability

An innovative two-step process with p-toluenesulfonic acid (p-TsOH) and oxidation treatment was proposed for the efficient preparation of carboxylated nanocellulose from hybrid Pennisetum. Approximately 90 % of lignin was dissolved by p-TsOH acid under the optimal condition (80 °C, 20 min). Near-complete delignification (down to 0.5 %) and introduction of carboxylate groups (up to 1.48 mmol/g) could be achieved simultaneously during cellulose oxidation treatments without the requirement for bleaching. However, different oxidation methods expressed different efficiency and sustainability. 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) oxidation has higher selectivity for the carboxylation reaction but with detriment to the aquatic environment. Fenton oxidation is more energy-consuming due to the lower carboxylate contents of products (maximum 188 μmol/g), with the carboxylic groups present as carboxylic acids, but competitive in terms of environmental sustainability, especially when renewable energy sources are available. The nanocelluloses obtained by the two oxidation methods differ in morphology and have different application prospects.

Efficient production of xylooligosaccharides from Camellia oleifera shells pretreated by pyruvic acid at lower temperature

XOS production from lignocellulose using organic carboxylic acids and alkyd acids has been widely reported. However, it still faces harsh challenges such as high energy consumption, high cost, and low purity. Pyruvic acid (PYA), a carbonyl acid with carbonyl and carboxyl groups, was used to produce XOS due to its stronger catalytic activity. In this work, XOS was efficiently prepared from COS in an autoclave under the condition of 0.21 M PYA-121 °C-35 min. The total yield of XOS reached 68.72 % without producing any toxic by-products, including furfural (FF) and 5-hydroxymethylfurfural (5-HMF). The yield of xylobiose (X2), xylotriose (X3), xylotetraose (X4), and xylopentaose (X5) were 20.58 %, 12.47 %, 15.74 %, and 10.05 %, respectively. Meanwhile, 89.05 % of lignin was retained in the solid residue, which provides a crucial functional group for synthesizing layered carbon materials (SRG-a). It achieves excellent electromagnetic shielding (EMS) performance through graphitization, reaching -30 dB at a thickness of 2.0 mm. The use of a PYA catalyst in the production of XOS has proven to be an efficient method due to lower temperature, lower acid consumption, and straightforward operation.

Xylooligosaccharides: A Bibliometric Analysis and Current Advances of This Bioactive Food Chemical as a Potential Product in Biorefineries' Portfolios

Xylooligosaccharides (XOS) are nondigestible compounds of great interest for food and pharmaceutical industries due to their beneficial prebiotic, antibacterial, antioxidant, and antitumor properties. The market size of XOS is increasing significantly, which makes its production from lignocellulosic biomass an interesting approach to the valorization of the hemicellulose fraction of biomass, which is currently underused. This review comprehensively discusses XOS production from lignocellulosic biomass, aiming at its application in integrated biorefineries. A bibliometric analysis is carried out highlighting the main players in the field. XOS production yields after different biomass pretreatment methods are critically discussed using Microsoft PowerBI® (2.92.706.0) software, which involves screening important trends for decision-making. Enzymatic hydrolysis and the major XOS purification strategies are also explored. Finally, the integration of XOS production into biorefineries, with special attention to economic and environmental aspects, is assessed, providing important information for the implementation of biorefineries containing XOS in their portfolio.

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.

Critical Techniques for Overcoming the Diffusion Limitations in Heterogeneously Catalytic Depolymerization of Lignin

Heterogeneously catalyzed depolymerization of lignin to value-added chemicals is increasingly attractive but highly challengeable. Particularly, the diffusion limitation of lignin macromolecule to the solid catalyst surface is a big barrier, which significantly decreases the yield of monomer while increasing char formation. Therefore, for the potential industrial utilization of lignin, new knowledge focused on the size of lignin particles is of great importance to offer guidance for promoting lignin depolymerization and suppressing condensation in the heterogeneously catalytic systems. In this Review, the size of lignin particles and macromolecules are summarized. Previous approaches for improving the mass diffusion including enhancing the solubility of lignin and exploitation of hierarchical and "solubilized" materials are also discussed. Based on these, a constructive perspective is proposed. Thus, this work provides a new insight on the rational design of heterogeneous catalytic techniques for efficient utilization of the aromatic polymer of lignin.

Nanogreen is the new future: the conversion of lignin and lignocellulosic wastes into nanomaterials

The lignocellulose biorefinery industry has assumed an important role within the current scenario. Lignin is an abundant and available biopolymer and one of the compounds present in the lignocellulosic waste. Therefore, processing lignin into new materials and nanomaterials, such as nanolignin, has attracted the attention of the scientific community. Lignin nanoparticles are materials that have excellent properties, such as biodegradability and non-toxicity, and have great potential as chelating agents, antimicrobials agents, UV protectors, nanofillers, adsorbents, catalysts, supercapacitors, emulsion stabilizers, delivered systems, drugs, and gene carriers. This review article covers the emergent scenario of nanolignin and the main aspects of scientific interest, such as the conversion and functionalization of lignin, the valorization of lignocellulose waste, and nanoparticle synthesis. A techno-economic evaluation of the biorefinery model of the nanolignin synthesis is presented based on the simulation of the process on the experimental and commercial databases available and reported by some authors. Finally, the techno-economic assessment is complemented by the life cycle assessment of various nanolignin synthesis pathways reported to evaluate the environmental implications and support this emergent technology development.

Recent advances in lignocellulosic and algal biomass pretreatment and its biorefinery approaches for biochemicals and bioenergy conversion

As the global demand for sustainable energy increases, lignocellulosic (such as agricultural residues, forest biomass, municipal waste, and dedicated energy crops) and algal (including macroalgae and microalgae) biomass have attracted considerable attention, because of their high availability of carbohydrates. This is a potential feedstock to produce biochemical and bioenergy. Pretreatment of biomass can disrupt their complex structure, increasing conversion efficiency and product yield. Therefore, this review comprehensively discusses recent advances in different pretreatments (physical, chemical, physicochemical, and biological pretreatments) for lignocellulosic and algal biomass and their biorefining methods. Life cycle assessment (LCA) which enables the quantification of the environmental impact assessment of a biorefinery also be introduced. Biorefinery processes such as raw material acquisition, extraction, production, waste accumulation, and waste conversion are all monitored under this concept. Nevertheless, there still exist some techno-economic barriers during biorefinery and extensive research is still needed to develop cost-effective processes.

Integrated biorefinery approaches for the industrialization of cellulosic ethanol fuel

Lignocellulosic biomass is an abundant and sustainable raw material, but its conversion into ethanol fuel has not yet achieved large-scale industrialization and economic benefits. Integrated biorefineries have been widely identified as the key to achieving this goal. Here, four promising routes were summarized to assemble the new industrial plants for cellulose-based fuels and chemicals, including 1) integration of cellulase production systems into current cellulosic ethanol processes; 2) combination of processes and facilities between cellulosic ethanol and first-generation ethanol; 3) application of enzyme-free saccharification processes and computational approaches to increase the bioethanol yield and optimize the integration process; 4) production of multiple products to maximize the value derived from the lignocellulosic biomass. Finally, the remaining challenges and perspectives of this field are also discussed.

Sustainable value added material use of occurring by-products from sugar and rice production in Vietnam

Due to the worldwide growing population, the demand on food increases, which results in the need for a higher productivity in agriculture. Generally, this leads to larger amounts of agricultural residues and by-products, which may cause severe environmental risks due to emissions from simple burning or storing, especially in emerging and developing countries. In Vietnam agricultural by-products arise in total of 118 Mt per year, whereas 80% are coming from rice and sugar cane processing. By the selection of favorable plant varieties, seed, and/or seedlings, it is possible to improve the rice and sugar yield. Besides, the by-products offer a great potential for a value-added material use. We developed a flexible portable, integrated process scheme aside from high-tech biotechnology applications. Erosion control blankets, soil improvers/composts for an improved crop yield and soil management, and adsorbents with the focus on environmental issues for cleaning of fluid streams were produced from different fractions of the residue fractions via thermo-mechanical processes. As a consequence, fossil raw material input streams, e.g. polymer based textiles, inorganic fertilizing agents, and peat/coal can be avoided. In laboratory and field tests we demonstrate the producibility and the applicability and summarize the positive impact of the aforementioned products made from rice straw and bagasse: The improved varieties as well as the addition of selected soil improvers/composts made from the by-products improve the test plants' yield and quality. The application of erosion control blankets prevents soil loss and dehydration by covering soil surface for a period of transition. The produced shaped activated carbons show mechanical and adsorption specific properties, which are comparable to commercial products.

Lignin removal improves xylooligosaccharides production from poplar by acetic acid hydrolysis

Organic acid hydrolysis is a potential method for xylooligosaccharides (XOS) production from lignocelluloses. However, the effect of lignin content on XOS production using organic acid hydrolysis remains unclear. In this work, the effect of delignification on XOS production from poplar by acetic acid (AC) hydrolysis was investigated. Hydrogen peroxide-acetic acid (HPAC) pretreatment catalyzed by 0-200 mM H₂SO₄ (HPAC0-HPAC200) removed 21.6-86.5% of lignin in poplar. HPAC pretreatment increased the xylan accessibility to AC solution, thus increasing the xylan removal during AC hydrolysis. An appropriate delignification (61.7%) resulted in the highest XOS yield of 37.4% by AC hydrolysis, increased by 29.9% compared to the optimal XOS yield (28.8%) from raw poplar. After alkaline post-incubation, the glucose yield of poplar residue rose from 57.1% to 78.6%. This work developed a delignification process to efficiently improve XOS and monosaccharides production from poplar.