Exploiting Nature's Most Abundant Polymers: Developing New Pathways for the Conversion of Cellulose, Hemicellulose, Lignin and Chitin into Platform Molecules (and Beyond)

Isolation and Structure Analysis of Chitin Obtained from Different Developmental Stages of the Mulberry Silkworm (Bombyx mori)

Chitin, a ubiquitous biopolymer, holds paramount scientific and economic significance. Historically, it has been primarily isolated from marine crustaceans. However, the surge in demand for chitin and the burgeoning interest in biopolymers have necessitated the exploration of alternative sources. Among these methods, the mulberry silkworm (Bombyx mori) has emerged as a particularly intriguing prospect. To isolate chitin from Bombyx mori, a chemical extraction methodology was employed. This process involved a series of meticulously orchestrated steps, including Folch extraction, demineralization, deproteinization, and decolorization. The resultant chitin was subjected to comprehensive analysis utilizing techniques such as attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), 13C nuclear magnetic resonance (NMR) spectroscopy, and wide-angle X-ray scattering (WAXS). The obtained results allow us to conclude that the Bombyx mori represents an attractive alternative source of α-chitin.

Polymers from Cellulosic Waste: Direct Polymerization of Levoglucosenone using DBU as a Catalyst

The bio-based platform molecule levoglucosenone (LGO) is now produced at multi-ton scale by the pyrolysis of cellulosic waste. As such it has become an industrially viable, non-petroleum-derived chemical feedstock. Herein we report the direct (one-step) and operationally simple polymerization of LGO that provides a highly sustainable method for polymer synthesis. Specifically, the ability of LGO to act as an electrophile has been harnessed so as to deliver high molecular weight polymers (Mn=236,000 g/mol, Đ=2.4) possessing excellent thermal stabilities (TD5 %=249 °C). Furthermore, there is a significant capacity for the effective chemical manipulation of these polymers as exemplified by treatment of them under Baeyer-Villiger conditions and so creating a simple and green route to hydrophilic materials. These one- and two-step transformations provide the most direct route to new, LGO-derived polymer scaffolds yet reported. E-factors of ca. 0.012 and atom economies of up to 99 % have been realized.

Sustainable Biomass Lignin-Based Hydrogels: A Review on Properties, Formulation, and Biomedical Applications

Different techniques have been developed to overcome the recalcitrant nature of lignocellulosic biomass and extract lignin biopolymer. Lignin has gained considerable interest owing to its attractive properties. These properties may be more beneficial when including lignin in the preparation of highly desired value-added products, including hydrogels. Lignin biopolymer, as one of the three major components of lignocellulosic biomaterials, has attracted significant interest in the biomedical field due to its biocompatibility, biodegradability, and antioxidant and antimicrobial activities. Its valorization by developing new hydrogels has increased in recent years. Furthermore, lignin-based hydrogels have shown great potential for various biomedical applications, and their copolymerization with other polymers and biopolymers further expands their possibilities. In this regard, lignin-based hydrogels can be synthesized by a variety of methods, including but not limited to interpenetrating polymer networks and polymerization, crosslinking copolymerization, crosslinking grafted lignin and monomers, atom transfer radical polymerization, and reversible addition-fragmentation transfer polymerization. As an example, the crosslinking mechanism of lignin-chitosan-poly(vinyl alcohol) (PVA) hydrogel involves active groups of lignin such as hydroxyl, carboxyl, and sulfonic groups that can form hydrogen bonds (with groups in the chemical structures of chitosan and/or PVA) and ionic bonds (with groups in the chemical structures of chitosan and/or PVA). The aim of this review paper is to provide a comprehensive overview of lignin-based hydrogels and their applications, focusing on the preparation and properties of lignin-based hydrogels and the biomedical applications of these hydrogels. In addition, we explore their potential in wound healing, drug delivery systems, and 3D bioprinting, showcasing the unique properties of lignin-based hydrogels that enable their successful utilization in these areas. Finally, we discuss future trends in the field and draw conclusions based on the findings presented.

Bioinspired Additive Manufacturing of Hierarchical Materials: From Biostructures to Functions

Throughout billions of years, biological systems have evolved sophisticated, multiscale hierarchical structures to adapt to changing environments. Biomaterials are synthesized under mild conditions through a bottom-up self-assembly process, utilizing substances from the surrounding environment, and meanwhile are regulated by genes and proteins. Additive manufacturing, which mimics this natural process, provides a promising approach to developing new materials with advantageous properties similar to natural biological materials. This review presents an overview of natural biomaterials, emphasizing their chemical and structural compositions at various scales, from the nanoscale to the macroscale, and the key mechanisms underlying their properties. Additionally, this review describes the designs, preparations, and applications of bioinspired multifunctional materials produced through additive manufacturing at different scales, including nano, micro, micro-macro, and macro levels. The review highlights the potential of bioinspired additive manufacturing to develop new functional materials and insights into future directions and prospects in this field. By summarizing the characteristics of natural biomaterials and their synthetic counterparts, this review inspires the development of new materials that can be utilized in various applications.

Bioconversion of a Lignocellulosic Hydrolysate to Single Cell Oil for Biofuel Production in a Cost-Efficient Fermentation Process

Cutaneotrichosporon oleaginosus is a highly efficient single cell oil producer, which in addition to hexoses and pentoses can metabolize organic acids. In this study, fed-batch cultivation with consumption-based acetic acid feeding was further developed to integrate the transformation of an industrial paper mill lignocellulosic hydrolysate (LCH) into yeast oil. Employing pentose-rich LCH as a carbon source instead of glucose significantly improved both biomass formation and lipid titer, reaching 55.73 ± 5.20 g/L and 42.1 ± 1.7 g/L (75.5% lipid per biomass), respectively. This hybrid approach of using acetic acid and LCH in one process was further optimized to increase the share of bioavailable carbon from LCH using a combination of consumption-based and continuous feeding. Finally, the techno-economic analysis revealed a 26% cost reduction when using LCH instead of commercial glucose. In summary, we developed a process leading to a holistic approach to valorizing a pentose-rich industrial waste by converting it into oleochemicals.

Haber-independent, asymmetric synthesis of the marine alkaloid epi-leptosphaerin from a chitin-derived chiral pool synthon

Chitin-derived platforms are emerging as valuable chemical entities for the construction of nitrogenous fine chemicals in processes independent of Haber ammonia. However, much of the work in this area has focused on achiral platforms that limit routine entry into enantiopure, bio-based N-chemical space. Herein, dihydroxyethyl acetamidofuran (Di-HAF), a chiral synthon readily available from chitin, has been transformed into the marine alkaloid epi-leptosphaerin. This work extends the fledgling Haber-independent synthesis concept to enantiopure chemical space not routinely accessible from existing achiral platforms.

Simple and modestly scalable synthesis of

The bio-derived platform molecule levoglucosenone (LGO, 1), which is the precursor to the green solvent Cyrene® (2), has been converted, at multi-gram scale, into its pseudo-enantiomer (iso-LGO, 2) and then reduced to iso-Cyrene (4). A less effective synthesis of this last compound from D-glucose is also described. Various physicochemical as well as certain toxicological properties of compound 4 are reported and compared to those established for the now commercially available Cyrene® (2). Such studies reveal that there are significant enough differences in the properties of the sustainably-derived Cyrene® (2) and isomer 4 (iso-Cyrene) to suggest they will exert complementary effects as solvents in a range of settings.

Sustainable lignin and lignin-derived compounds as potential therapeutic agents for degenerative orthopaedic diseases: A systemic review

Lignin, the most abundant natural and sustainable phenolic compound in biomass, has exhibited medicinal values due to its biological activities decided by physicochemical properties. Recently, the lignin and its derivatives (such as lignosulfonates and lignosulfonate) have been proven efficient in regulating cellular process and the extracellular microenvironment, which has been regarded as the key factor in disease progression. In orthopaedic diseases, especially the degenerative diseases represented by osteoarthritis and osteoporosis, excessive activated inflammation has been proven as a key stage in the pathological process. Due to the excellent biocompatibility, antibacterial and antioxidative activities of lignin and its derivatives, they have been applied to stimulate cells and restore the uncoupling bone remodeling in the degenerative orthopaedic diseases. However, there is a lack of a systemic review to state the current research actuality of lignin and lignin-derived compounds in treating degenerative orthopaedic diseases. Herein, we summarized the current application of lignin and lignin-derived compounds in orthopaedic diseases and proposed their possible therapeutic mechanism in treating degenerative orthopaedic diseases. It is hoped this work could guide the future preparation of lignin/lignin-derived drugs and implants as available therapeutic strategies for clinically degenerative orthopaedic diseases.

Depolymerization and Hydrogenation of Organosolv Eucalyptus Lignin by Using Nickel Raney Catalyst

The use of lignocellulosic biomass to obtain biofuels and chemicals produces a large amount of lignin as a byproduct. Lignin valorization into chemicals needs efficient conversion processes to be developed. In this work, hydrocracking of organosolv lignin was performed by using nickel Raney catalyst. Organosolv lignin was obtained from the pretreatment of eucalyptus wood at 170 °C for 1 h by using 1/100/100 (w/v/v) ratio of biomass/oxalic acid solution (0.4% w/w)/1-butanol. The resulting organic phase of lignin in 1-butanol was used in hydrogenation tests. The conversion of lignin was carried out with a batch reactor equipped with a 0.3 L vessel with adjustable internal stirrer and heat control. The reactor was pressurized at 5 bar with hydrogen at room temperature, and then the temperature was raised to 250 °C and kept for 30 min. Operative conditions were optimized to achieve high conversion in monomers and to minimize the loss of solvent. At the best performance conditions, about 10 wt % of the lignin was solubilized into monomeric phenols. The need to find a trade-off between lignin conversion and solvent side reaction was highlighted.