Correlation between physicochemical characteristics of lignin deposited on autohydrolyzed wood chips and their cellulase enzymatic hydrolysis

Lignin fractionation and condensation in aromatic-additive-assisted acidic pretreatment and their influence on lignin's effect on the enzymatic hydrolysis

Factors influencing inhibition of lignin on the enzymatic hydrolysis have not been fully elucidated. This study aims to elucidate the effects of lignin fractionation and condensation on its inhibition on enzymatic hydrolysis in aromatic-additive-assisted acidic pretreatment using 2-naphthol (2 N), 2-naphthol-7-sulfonate (NS), and resorcinol (RS). Through simulation reactions of pretreatment and physiochemical analyses of ethanol-extractable lignins (ELs) and cellulolytic enzyme lignins (CELs) from pretreatment, it was observed that 2 N addition in the acidic pretreatment could suppress lignin condensation. This suppression consequently mitigated inhibition of EL-AP-2 N on the enzymatic hydrolysis of Avicel. Simultaneously, addition of NS in the pretreatment can enhance lignin fractionation by facilitating decomposition of lignin into water and ethanol soluble fractions, thereby mitigating inhibition of CEL-AP-NS on the enzymatic hydrolysis. Meanwhile, with RS in the pretreatment, EL-AP-RS and CEL-AP-RS demonstrated the most pronounced inhibition among ELs and CELs. This inhibition may be attributed to the increased phenolic OH groups with the introduction of RS units. A heatmap analysis revealing relationship between lignin characteristics and its inhibition indicated that ELs exhibit reduced inhibition on enzymatic hydrolysis when lignin condensation was suppressed. Conversely, CELs would show diminished inhibitory effects when lignin particle sizes were smaller and lignin fractionation was stronger.

Ferulic acid triggering a co-production of 4-vinyl guaiacol and fumaric acid from lignocellulose-based carbon source by Rhizopus oryzae

Plant secondary metabolites have attracted considerable attention due to the increasing demand for finite fossil resources and environmental concerns. However, the biosynthesis of aromatic aldehydes or alcohols from renewable resources remains challenging and costly. This study explores a novel approach performed by the aromatic catabolizing organism Rhizopus oryzae, which enables a ferulic acid-activated co-production of 4-vinyl guaiacol (4-VG) and fumaric acid. The strain produced 4.60 g/L 4-VG and 11.25 g/L fumaric acid from a mixed carbon source of glucose and xylose, suggesting that this new pathway allows the potential production of natural 4-VG from low-cost substrates. This green route, which utilizes Rhizopus oryzae's ability to efficiently convert various renewable resources into valuable chemicals, paves the way for improved catalytic efficiency in 4-VG production.

Lignins as Promising Renewable Biopolymers and Bioactive Compounds for High-Performance Materials

The recycling of biomass into high-value-added materials requires important developments in research and technology to create a sustainable circular economy. Lignin, as a component of biomass, is a multipurpose aromatic polymer with a significant potential to be used as a renewable bioresource in many fields in which it acts both as promising biopolymer and bioactive compound. This comprehensive review gives brief insights into the recent research and technological trends on the potential of lignin development and utilization. It is divided into ten main sections, starting with an outlook on its diversity; main properties and possibilities to be used as a raw material for fuels, aromatic chemicals, plastics, or thermoset substitutes; and new developments in the use of lignin as a bioactive compound and in nanoparticles, hydrogels, 3D-printing-based lignin biomaterials, new sustainable biomaterials, and energy production and storage. In each section are presented recent developments in the preparation of lignin-based biomaterials, especially the green approaches to obtaining nanoparticles, hydrogels, and multifunctional materials as blends and bio(nano)composites; most suitable lignin type for each category of the envisaged products; main properties of the obtained lignin-based materials, etc. Different application categories of lignin within various sectors, which could provide completely sustainable energy conversion, such as in agriculture and environment protection, food packaging, biomedicine, and cosmetics, are also described. The medical and therapeutic potential of lignin-derived materials is evidenced in applications such as antimicrobial, antiviral, and antitumor agents; carriers for drug delivery systems with controlled/targeting drug release; tissue engineering and wound healing; and coatings, natural sunscreen, and surfactants. Lignin is mainly used for fuel, and, recently, studies highlighted more sustainable bioenergy production technologies, such as the supercapacitor electrode, photocatalysts, and photovoltaics.

Understanding of promoting enzymatic hydrolysis of combined hydrothermal and deep eutectic solvent pretreated poplars by Tween 80

In this study, lignin blockers including non-catalytic protein and surfactants were employed to promote enzymatic digestibility of pretreated poplars. Among them, Tween 80 exhibited the most pronounced facilitation, improving the glucose yield from 26.6% to 99.6% at a low enzyme loading (10 FPU/g glucan), and readily reduced the required cellulase loading by 75%. The underlying mechanism for this remarkable improvement on glucose yields by Tween 80 was elucidated. The impacts of Tween 80 on the enzyme-lignin interaction were explored by quartz crystal microbalance analysis, revealing that the binding rate of Tween 80 on lignin surfaces was 3-fold higher than that of enzyme. More importantly, Tween 80 remarkably decreased the binding capacity and binding rate of enzyme on lignins. Furthermore, the substrate properties dominating the increase in glucose yields with Tween 80 were explored. The results facilitate to understand the underlying mechanism of the promotion of surfactants on enzymatic hydrolysis.

Research Progress on Lignocellulosic Biomass Degradation Catalyzed by Enzymatic Nanomaterials

Lignocellulose biomass (LCB) has extensive applications in many fields such as bioenergy, food, medicines, and raw materials for producing value-added products. One of the keys to efficient utilization of LCB is to obtain directly available oligo- and monomers (e.g., glucose). With the characteristics of easy recovery and separation, high efficiency, economy, and environmental protection, immobilized enzymes have been developed as heterogeneous catalysts to degrade LCB effectively. In this review, applications and mechanisms of LCB-degrading enzymes are discussed, and the nanomaterials and methods used to immobilize enzymes are also discussed. Finally, the research progress of lignocellulose biodegradation catalyzed by nano-enzymes was discussed.