Exploring the action of endoglucanases on bleached eucalyptus kraft pulp as potential catalyst for isolation of cellulose nanocrystals

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.

Taguchi-assisted multi-response improved simultaneous nanocellulose and sugar production from microcrystalline cellulose derived from raw oil palm leaves

Enzymatic treatment on lignocellulosic biomass has become a trend in preparing nanocellulose (NC), but the process must be optimized to guarantee high production yield and crystallinity. This study offers insights into an innovative protocol using cultivated fungal cellulase and xylanase to improve NC production from raw oil palm leaves (OPL) using five-factor-four-level Taguchi orthogonal design for optimizing parameters, namely substrate and enzyme loading, surfactant concentration, incubation temperature and time. Statistical results revealed the best condition for producing NC (66.06 % crystallinity, 43.59 % yield) required 10 % (w/v) substrate, 1 % (v/v) enzyme, 1.4 % (w/v) Tween-80, with 72-h incubation at 30 °C. Likewise, the highest sugar yield (47.07 %) was obtained using 2.5 % (w/v) substrate, 2.0 % (v/v) enzyme, 2.0 % (w/v) Tween-80, with 72-h incubation at 60 °C. The auxiliary enzymes used in this study, i.e., xylanase, produced higher crystallinity NC, showing widths between 8 and 12 nm and lengths >1 μm and sugars at 47.07 % yield. Thus, our findings proved that optimizing the single-step enzymatic hydrolysis of raw OPL could satisfactorily produce relatively crystalline NC and sugar yield for further transformation into bio-nanocomposites and biofuels. This study presented a simple, innovative protocol for NC synthesis showing characteristics comparable to the traditionally-prepared NC, which is vital for material's commercialization.

Exploring xylan removal via enzymatic post-treatment to tailor the properties of cellulose nanofibrils for packaging film applications

Hemicellulose plays a key role in both the production of cellulose nanofibrils (CNF) and their properties as suspensions and films. While the use of enzymatic and chemical pre-treatments for tailoring hemicellulose levels is well-established, post-treatment methods using enzymes remain relatively underexplored and hold significant promise for modifying CNF film properties. This study aimed to investigate the effects of enzymatic xylan removal on the properties of CNF film for packaging applications. The enzymatic post-treatment was carried out using an enzymatic cocktail enriched with endoxylanase (EX). The EX post-treated-CNFs were characterized by LALLS, XRD, and FEG-SEM, while their films were characterized in terms of physical, morphological, optical, thermal, mechanical, and barrier properties. Employing varying levels of EX facilitated the hydrolysis of 8 to 35 % of xylan, yielding CNFs with different xylan contents. Xylan was found to be vital for the stability of CNF suspensions, as its removal led to the agglomeration of nanofibrils. Nanostructures with preserved crystalline structures and different morphologies, including nanofibers, nanorods, and their hybrids were observed. The EX post-treatment contributed to a smoother film surface, improved thermostability, and better moisture barrier properties. However, as the xylan content decreased, the films became lighter (lower grammage), less strong, and more brittle. Thus, the enzymatic removal of xylan enabled the customization of CNF films' performance without affecting the inherent crystalline structure, resulting in materials with diverse functionalities that could be explored for use in packaging films.

Comprehensive review on recent trends and perspectives of natural exo-polysaccharides: Pioneering nano-biotechnological tools

Exopolysaccharides (EPSs), originating from various microbes, and mushrooms, excel in their conventional role in bioremediation to showcase diverse applications emphasizing nanobiotechnology including nano-drug carriers, nano-excipients, medication and/or cell encapsulation, gene delivery, tissue engineering, diagnostics, and associated treatments. Acknowledged for contributions to adsorption, nutrition, and biomedicine, EPSs are emerging as appealing alternatives to traditional polymers, for biodegradability and biocompatibility. This article shifts away from the conventional utility to delve deeply into the expansive landscape of EPS applications, particularly highlighting their integration into cutting-edge nanobiotechnological methods. Exploring EPS synthesis, extraction, composition, and properties, the discussion emphasizes their structural diversity with molecular weight and heteropolymer compositions. Their role as raw materials for value-added products takes center stage, with critical insights into recent applications in nanobiotechnology. The multifaceted potential, biological relevance, and commercial applicability of EPSs in contemporary research and industry align with the nanotechnological advancements coupled with biotechnological nano-cleansing agents are highlighted. EPS-based nanostructures for biological applications have a bright future ahead of them. Providing crucial information for present and future practices, this review sheds light on how eco-friendly EPSs derived from microbial biomass of terrestrial and aquatic environments can be used to better understand contemporary nanobiotechnology for the benefit of society.

Construction and biological effects of a redox-enzyme dual-responsive lufenuron nano-controlled release formulation

BACKGROUND

Pesticide formulations based on nanotechnology can effectively improve the efficiency of pesticide utilization and reduce pesticide residues in the environment. In this study, mesoporous silica nanoparticles containing disulfide bonds were synthesized by the sol-gel method, carboxylated and adsorbed with lufenuron, and grafted with cellulose to obtain a lufenuron-loaded nano-controlled release formulation (Luf@MSNs-ss-cellulose).

RESULTS

The structure and properties of Luf@MSNs-ss-cellulose were characterized. The results showed that Luf@MSNs-ss-cellulose exhibits a regular spherical shape with 12.41% pesticide loading. The highest cumulative release rate (73.46%) of this pesticide-loaded nanoparticle was observed at 7 days in the environment of glutathione and cellulase, which shows redox-enzyme dual-responsive performance. As a result of cellulose grafting, Luf@MSNs-ss-cellulose had a small contact angle and high adhesion work on corn leaves, indicating good wetting and adhesion properties. After 14 days of spraying with 20 mg L-1 formulations in the long-term control efficacy experiment, the mortality of Luf@MSNs-ss-cellulose against Ostrinia furnacalis larvae (56.67%) was significantly higher than that of commercial Luf@EW (36.67%). Luf@MSNs-ss-cellulose is safer for earthworms and L02 cells.

CONCLUSION

The nano-controlled release formulation obtained in this study achieved intelligent pesticide delivery in time and space under the environmental stimulation of glutathione and cellulase, providing an effective method for the development of novel pesticide delivery systems. © 2023 Society of Chemical Industry.

Biotechnological innovations in nanocellulose production from waste biomass with a focus on pineapple waste

New materials' synthesis and utilization have shown many critical challenges in healthcare and other industrial sectors as most of these materials are directly or indirectly developed from fossil fuel resources. Environmental regulations and sustainability concepts have promoted the use of natural compounds with unique structures and properties that can be biodegradable, biocompatible, and eco-friendly. In this context, nanocellulose (NC) utility in different sectors and industries is reported due to their unique properties including biocompatibility and antimicrobial characteristics. The bacterial nanocellulose (BNC)-based materials have been synthesized by bacterial cells and extracted from plant waste materials including pineapple plant waste biomass. These materials have been utilized in the form of nanofibers and nanocrystals. These materials are found to have excellent surface properties, low density, and good transparency, and are rich in hydroxyl groups for their modifications to other useful products. These materials are well utilized in different sectors including biomedical or health care centres, nanocomposite materials, supercapacitors, and polymer matrix production. This review explores different approaches for NC production from pineapple waste residues using biotechnological interventions, approaches for their modification, and wider applications in different sectors. Recent technological developments in NC production by enzymatic treatment are critically discussed. The utilization of pineapple waste-derived NC from a bioeconomic perspective is summarized in the paper. The chemical composition and properties of nanocellulose extracted from pineapple waste may have unique characteristics compared to other sources. Pineapple waste for nanocellulose production aligns with the principles of sustainability, waste reduction, and innovation, making it a promising and novel approach in the field of nanocellulose materials.

Cellulose Isolation from Tomato Pomace: Part II-Integrating High-Pressure Homogenization in a Cascade Hydrolysis Process for the Recovery of Nanostructured Cellulose and Bioactive Molecules

This work proposes a biorefinery approach for utilizing tomato pomace (TP) through a top-down deconstructing strategy, combining mild chemical hydrolysis with high-pressure homogenization (HPH). The objective of the study is to isolate cellulose pulp using different combinations of chemical and physical processes: (i) direct HPH treatment of the raw material, (ii) HPH treatment following acid hydrolysis, and (iii) HPH treatment following alkaline hydrolysis. The results demonstrate that these isolation routes enable the production of cellulose with tailored morphological properties from TP with higher yields (up to +21% when HPH was applied before hydrolysis and approximately +6% when applied after acid or after alkaline hydrolysis). Additionally, the side streams generated by this cascade process show a four-fold increase in phenolic compounds when HPH is integrated after acid hydrolysis compared to untreated sample, and they also contain nanoparticles composed of hemicellulose and lignin, as shown by FT-IR and SEM. Notably, the further application of HPH treatment enables the production of nanostructured cellulose from cellulose pulp derived from TP, offering tunable properties. This approach presents a sustainable pathway for the extraction of cellulose and nanocellulose, as well as the valorization of value-added compounds found in residual biomass in the form of side streams.

Preparation of cellulose nanocrystals from commercial dissolving pulp using an engineered cellulase system

There is increasing attention to the production of cellulose nanocrystals (CNCs) from lignocellulosic biomass by enzymatic hydrolysis with cellulase. In this study, the feasibility of the application of a cellulase system from engineered strain Penicillium oxalicum cEES in the production of CNCs was assessed. Using commercial eucalyptus dissolving pulp (EDP) as substrate, the CNCs were successfully obtained by enzymatic hydrolysis with the cellulase cEES, and the total yields of CNCs reached 15.7% through three-step enzymatic hydrolysis of total 72 h (24 h for each step). The prepared CNCs were characterized and found that their crystallinity and thermal stability were higher than that of EDP. In the later stage of enzymatic hydrolysis, the process efficiency of enzymatic preparation of CNCs greatly decreased because of the high crystallinity of cellulosic substrate, and a simple homogenization treatment can promote the enzymatic hydrolysis, as well as produce fusiform CNCs with more uniform size and more fermentable sugar that could be further converted into fuels and bulk chemicals through fermentation. This study provides a feasible enzymatic preparation process for CNCs with engineered cellulase and commercial cellulosic materials.

Production and Characterization of Cellulose Nanocrystals from Eucalyptus Dissolving Pulp Using Endoglucanases from Myceliophthora thermophila

Endoglucanase (EG) is a key enzyme during enzymatic preparation of cellulose nanocrystals (CNCs). Myceliophthora thermophila is a thermophilic fungus that has thermal properties and a high secretion of endoglucanases (EGs), and could serve as potential sources of EGs for the preparation of CNCs. In this work, four different GH families (GH5, GH7, GH12, and GH45) of EGs from M. thermophila were expressed and purified, and their enzymatic characteristics and feasibility of application in CNC preparation were investigated. It was shown that the MtEG5A from M. thermophila has good potential in the enzymatic preparation of CNCs using eucalyptus dissolving pulp as feedstock. It was also observed that there was a synergistic effect between the MtEG5A and other MtEGs in the preparation of CNCs, which improved the yield and properties of CNCs obtained by enzymatic hydrolysis. This study provides a reference for understanding the enzymatic characteristics of different families of EGs from M. thermophile and their potential application in nanocellulose production.

High-yield production of rod-like and spherical nanocellulose by controlled enzymatic hydrolysis of mechanically pretreated cellulose

In this study, a simple and scalable mechanical pretreatment was evaluated as means to increase the cellulose accessibility of cellulose fibers, with the aim of improving the efficiency of enzymatic reactions for the production of cellulose nanoparticles (CNs). In addition, the effects of enzyme type (endoglucanase - EG, endoxylanase - EX, and a cellulase preparation - CB), composition ratio (0-200UEG:0-200UEX or EG, EX, and CB alone), and loading (0 U-200 U) were investigated in relation to CN yield, morphology, and properties. The combination of mechanical pretreatment and specific conditions for enzymatic hydrolysis substantially improved CN production yield, reaching up to 83 %. The production of rod-like or spherical nanoparticles and their chemical composition were highly dependent on the type of enzyme, composition ratio, and loading. However, these enzymatic conditions minimally affected the crystallinity index (approximately 80 %) and thermal stability (T_max within 330-355 °C). Collectively, these results demonstrate that mechanical pretreatment followed by enzymatic hydrolysis under specific conditions is a suitable method to produce nanocellulose with a high yield and tunable properties such as purity, rod-like or spherical forms, high thermal stability, and high crystallinity. Therefore, this production route is a promising approach to produce tailored CNs with the potential to offer superior performance in a variety of sophisticated applications, including, but not limited to, wound dressings, drug delivery, thermoplastic composites, 3D (bio)printing, and smart packaging.

Endoglucanase effects on energy consumption in mechanical fibrillation of cellulose fibers into nanocelluloses

Enzymatic processing is seen as a promising means of moving toward environment-friendly industrial processes such as the use of endoglucanase (EG) enzyme in the production of nanocellulose. However, the properties that make EG pretreatment effective in the isolation of fibrillated cellulose remain a subject of debate. To address this issue, we considered EGs from four glycosyl hydrolase (GH) families (5, 6, 7 and 12) and investigated the roles of the tri-dimensional structures and catalytic features depending on the presence of a carbohydrate binding module (CBM). By using eucalyptus Kraft wood fibers, we produced cellulose nanofibrils (CNF) using mild enzymatic pretreatment followed by disc ultra-refining. Compared with the control (in the absence of pretreatment), the GH5 and GH12 enzymes (CBM free) reduced the fibrillation energy by approximately 15 %. The most efficient energy reduction, 25 and 32 %, was achieved with GH5 and GH6 linked to CBM, respectively. They improved the rheological properties of the CNF suspensions (noting that neither of these EGs released soluble products). Interestingly, while the hydrolytic activity was significant (released soluble products), GH7-CBM did not lead to a reduction in fibrillation energy. Hence, the large molecular weight and wide cleft of GH7-CBM led to soluble sugar release but contributed little to fibrillation. Our findings suggest that the improved fibrillation observed upon EG pretreatment is not a consequence of hydrolytic activity or release of products but mostly related to efficient adsorption on the substrate and modification of the surface viscoelastic (amorphogenesis).

Study on the effects of different pectinase/cellulase ratios and pretreatment times on the preparation of nanocellulose by ultrasound-assisted bio-enzyme heat treatment

With the development of science and technology, efficient, fast and green methods are increasingly being pursued. The production of nanocellulose by green methods, such as bio-enzymes-assisted ultrasound treatment, has been the focus of many studies. However, the yield of cellulose nanocrystals prepared by this method is very low. In this paper, by pretreatment of microcrystalline cellulose (MCC), nanocellulose was prepared by heating and stirring + pectinase/cellulase + ultrasonic treatment (HSt - P/C - Ultr). The effects of the ratios of pectinase and cellulase and the hydrolysis time on the yield of nanocellulose were studied. FTIR, XRD, SEM, TEM and TG were used to determine the structure, crystallinity, morphology and thermal stability of nanocellulose. The results showed that optimal hydrolysis conditions were determined as a pectinase : cellulase ratio of 1 : 1, 90 min and 50 °C. The yield of nanocellulose was about 32.0%. The yield of pectinase cellulase = 1 : 1 was higher than that of microcrystalline cellulose (MCC) treated by a single bio-enzyme. This indicated that the synergistic effects of pectinase and cellulase have a certain effect on the formation of nanocellulose. During the preparation, the crystalline form of cellulose did not change. It was still cellulose I with a crystallinity of 73.5%, which is 9.50% higher than that of microcrystalline cellulose (MCC), a width of 20-50 nm, a high aspect ratio and a winding network structure. Therefore, nanocellulose prepared by this method is an ideal toughening material for manufacturing composite materials.

Valorization of wheat straw in food packaging: A source of cellulose

Wheat straw (WS) is one of the abundant categories of agricultural waste, which is usually abandoned and burned yearly, thus creating environmental issues. Traditionally, it is used for low-value purposes, mainly in cattle feeding or agricultural mulch, and the rest is burnt or thrown away. WS is a valuable candidate as raw material for being used as reinforcing fibers to fabricate biocomposites. Among existing strategies, one of the potential strategies to utilize such lignocellulosic biomasses includes the extraction of cellulose as a potential candidate in the fabrication of sustainable packaging. Exploring WS as a valuable source of cellulose could be a key strategy for enabling biopolymers in packaging, which relies on developing tailor-made materials from non-food and low-cost resources. In this regard, the valorization of WSs for packaging can add value to these underutilized residues and successfully contribute to the circular economy concept. The review addresses the valorization of WS as a source of cellulose and its nanostructured forms for food packaging applications. The review also discusses cellulose derivatives extraction using conventional or innovative techniques (microwave-assisted extraction, fractionation, mechanical fibrillation, steam-explosion, microfludization, enzymatic hydrolysis, etc.). The different applications of these extracted biopolymers in the packaging are also summarized.

Valorization of nano-based lignocellulosic derivatives to procure commercially significant value-added products for biomedical applications

Biowaste, produced from nature, is preferred to be a good source of carbon and ligninolytic machinery for many microorganisms. They are complex biopolymers composed of lignin, cellulose, and hemicellulose traces. This biomass can be depolymerized to its nano-dimensions to gain exceptional properties useful in the field of cosmetics, pharmaceuticals, high-strength materials, etc. Nano-sized biomass derivatives overcome the inherent drawbacks of the parent material and offer promises as a potential material for a wide range of applications with their unique traits such as low-toxicity, biocompatibility, biodegradability and environmentally friendly nature with versatility. This review focuses on the production of value-added products feasible from nanocellulose, nano lignin, and xylan nanoparticles which is quite a novel study of its kind. Dawn of nanotechnology has converted bio waste by-products (hemicellulose and lignin) into useful precursors for many commercial products. Nano-cellulose has been employed in the fields of electronics, cosmetics, drug delivery, scaffolds, fillers, packaging, and engineering structures. Xylan nanoparticles and nano lignin have numerous applications as stabilizers, additives, textiles, adhesives, emulsifiers, and prodrugs for many polyphenols with an encapsulation efficiency of 50%. This study will support the potential development of composites for emerging applications in all aspects of interest and open up novel paths for multifunctional biomaterials in nano-dimensions for cosmetic, drug carrier, and clinical applications.

Brazilian Agro-industrial Wastes as Potential Textile and Other Raw Materials: a Sustainable Approach

The Brazilian agro-industrial chain generates about 291 million/tons/year of wastes, which, if inadequately destinated, could originate social and environmental risks. There is a growing need for the use of alternative raw materials to replace that originated from fossil resources in the Brazilian industry. Renewable materials play an important role on the sustainability of ecosystems and materials’ circularity. The issue has acquired importance in light of recent bio-based agro-fiber development potential applications. Considering sustainability guidelines, this study aimed to analyze the main Brazilian agro-industrial waste crops (temporary and permanent) as important sources of natural fibers and other raw materials. A systematic review of the literature (SRL) about Brazilian researches, based on concepts of industrial ecology, and the creation of a bibliometric analysis network were carried out. The agricultural biomass related to the main crops presents characteristics making them suitable to be applied for textiles, as natural fibers and polymers, in biosorbents for industrial effluents, and cellulose obtention and reinforcement material in composites. Thus, scientific investment in researches on materials and technology development are necessary to provide applications that could meet current and future demands and expand the scope of new materials for sustainability.

Ultrasonic cavitation: An effective cleaner and greener intensification technology in the extraction and surface modification of nanocellulose

With rising consumer demand for natural products, a greener and cleaner technology, i.e., ultrasound-assisted extraction, has received immense attention given its effective and rapid isolation for nanocellulose compared to conventional methods. Nevertheless, the application of ultrasound on a commercial scale is limited due to the challenges associated with process optimization, high energy requirement, difficulty in equipment design and process scale-up, safety and regulatory issues. This review aims to narrow the research gap by placing the current research activities into perspectives and highlighting the diversified applications, significant roles, and potentials of ultrasound to ease future developments. In recent years, enhancements have been reported with ultrasound assistance, including a reduction in extraction duration, minimization of the reliance on harmful chemicals, and, most importantly, improved yield and properties of nanocellulose. An extensive review of the strengths and weaknesses of ultrasound-assisted treatments has also been considered. Essentially, the cavitation phenomena enhance the extraction efficiency through an increased mass transfer rate between the substrate and solvent due to the implosion of microbubbles. Optimization of process parameters such as ultrasonic intensity, duration, and frequency have indicated their significance for improved efficiency.

Biorefinery of apple pomace: New insights into xyloglucan building blocks

Within the apple pomace biorefinery cascade processing framework aiming at adding value to an agroindustrial waste, after pectin recovery, this study focused on hemicellulose. The structure of the major apple hemicellulose, xyloglucan (XyG), was assessed as a prerequisite to potential developments in industrial applications. DMSO-LiCl and 4 M KOH soluble hemicelluloses from pectin-extracted apple pomace were purified by anion exchange chromatography. XyG structure was assessed by coupling xyloglucanase and endo-β-1,4-glucanase digestions to HPAEC and MALDI-TOF MS analyses. 71.9% of pomaces hemicellulose were recovered with starch. DMSO-LiCl and 4 M KOH soluble XyG exhibited Mw of 19 and 140 kDa, respectively. Besides the XXXG, XLXG, XXLG, XXFG, XLFG and XLLG structures, novel oligosaccharides with degree of polymerization of 6-10 were observed after xyloglucanase digestion. Cellobiose and cellotriose were revealed randomly distributed in XyG backbone and were more present in DMSO-LiCl soluble XyG. Residual pomace remains a potential source of other materials.

Xylanase increases the selectivity of the enzymatic hydrolysis with endoglucanase to produce cellulose nanocrystals with improved properties

Enzyme-mediated isolation of cellulose nanocrystals (CNCs) is a promising environment friendly method with expected lower capital and operating expenditures compared to traditional processes. However, it is still poorly understood. In this study, an endoxylanase was applied as accessory enzyme to assess its potential to increase the selectivity of an endoglucanase during cellulose hydrolysis to isolate CNCs with improved properties. Only combinations of the enzymes with xylanase activity equal to or higher than the endoglucanase activity resulted in CNCs with improved properties (i.e., crystallinity, thermostability, uniformity, suspension stability and aspect ratio). The beneficial effects of the accessory enzyme are related to its hydrolytic (xylan and cellulose hydrolysis) and non-hydrolytic action (swelling of cellulose fibers and fiber porosity) and on the ratio of the enzymes, which in turn allows to tailor the properties of the CNCs. In conclusion, compared to the traditional sulfuric acid hydrolysis method, accessory enzymes help to isolate cellulose nanomaterials with improved and customized (sizes, aspect ratio and morphology) properties that may allow for new applications.

Biomedical engineering aspects of nanocellulose: a review

Cellulose is one of the most abundant renewable biopolymer in nature and is present as major constituent in both plant cell walls as well as synthesized by some microorganisms as extracellular products. In both the systems, cellulose self-assembles into a hierarchical ordered architecture to form micro to nano-fibrillated structures, on basis of which it is classified into various forms. Nanocellulose (NCs) exist as rod-shaped highly crystalline cellulose nanocrystals to high aspect ratio cellulose nanofibers, micro-fibrillated cellulose and bacterial cellulose (BC), depending upon the origin, structural and morphological properties. Moreover, NCs have been processed into diversified products ranging from composite films, coatings, hydrogels, aerogels, xerogels, organogels, rheological modifiers, optically active birefringent colored films using traditional-to-advanced manufacturing techniques. With such versatility in structure-property, NCs have profound application in areas of healthcare, packaging, cosmetics, energy, food, electronics, bioremediation, and biomedicine with promising commercial potential. Herein this review, we highlight the recent advancements in synthesis, fabrication, processing of NCs, with strategic chemical modification routes to tailor its properties for targeted biomedical applications. We also study the basic mechanism and models for biosynthesis of cellulose in both plant and microbial systems and understand the structural insights of NC polymorphism. The kinetics study for both enzymatic/chemical modifications of NCs and microbial growth behavior of BC under various reactor configurations are studied. The challenges associated with the commercial aspects as well as industrial scale production of pristine and functionalized NCs to meet the growing demands of market are discussed and prospective strategies to mitigate them are described. Finally, post chemical modification evaluation of biological and inherent properties of NC are important to determine their efficacy for development of various products and technologies directed for biomedical applications.

Cellulose nanostructures obtained using enzymatic cocktails with different compositions

Cellulose nanostructures obtained from lignocellulosic biomass by the enzymatic route can offer advantages in terms of material properties and processing sustainability. However, most of the enzymatic cocktails commonly used in the saccharification of biomass are designed to promote the complete depolymerization of the cellulose structure into soluble sugars. Here, investigation was made of the way that the action of different commercially available cellulase enzyme cocktails can affect the production of nanocellulose. For this, enzymatic cocktails designed for complete or partial saccharification were compared, using eucalyptus cellulose pulp as a model feedstock. The results showed that all the enzymatic cocktails were effective in the formation of nanocellulose structures, with the complete saccharification enzymes being more efficient in promoting the coproduction of glucose (36.5 g/L, 87% cellulose conversion). The presence of auxiliary enzymes, especially xylanases, acted cooperatively to favor the production of nanostructures with higher crystallinity (up to 79%), higher surface charge (zeta potential up to -30.9 mV), and more uniform dimensions within the size range of cellulose nanocrystals (80 to 350 nm). Interestingly, for the enzymatic cocktails designed for partial saccharification, the xylanase activity was more important than the endoglucanase activity in the production of nanocellulose with improved properties. The findings showed that the composition of the enzymatic cocktails already used for complete biomass saccharification can be suitable for obtaining nanocellulose, together with the release of a glucose stream, in a format compatible with the biorefinery concept.

Emerging Developments on Nanocellulose as Liquid Crystals: A Biomimetic Approach

Biomimetics is the field of obtaining ideas from nature that can be applied in science, engineering, and medicine. The usefulness of cellulose nanocrystals (CNC) and their excellent characteristics in biomimetic applications are exciting and promising areas of present and future research. CNCs are bio-based nanostructured material that can be isolated from several natural biomasses. The CNCs are one-dimensional with a high aspect ratio. They possess high crystalline order and high chirality when they are allowed to assemble in concentrated dispersions. Recent studies have demonstrated that CNCs possess remarkable optical and chemical properties that can be used to fabricate liquid crystals. Research is present in the early stage to develop CNC-based solvent-free liquid crystals that behave like both crystalline solids and liquids and exhibit the phenomenon of birefringence in anisotropic media. All these characteristics are beneficial for several biomimetic applications. Moreover, the films of CNC show the property of iridescent colors, making it suitable for photonic applications in various devices, such as electro-optical devices and flat panel displays.

Lytic polysaccharide monooxygenases as powerful tools in enzymatically assisted preparation of nano-scaled cellulose from lignocellulose: A review

Nanocellulose, either in the form of fibers or crystals, constitutes a renewable, biobased, biocompatible material with advantageous mechanical properties that can be isolated from lignocellulosic biomass. Enzyme-assisted isolation of nanocellulose is an attractive, environmentally friendly approach that leads to products of higher quality compared to their chemically prepared counterparts. Lytic polysaccharide monooxygenases (LPMOs) are enzymes that oxidatively cleave the β-1,4-glycosidic bond of polysaccharides upon activation of O₂ or H₂O₂ and presence of an electron donor. Their use for treatment of cellulose fibers towards the preparation of nano-scaled cellulose is related to the ability of LPMOs to create nicking points on the fiber surface, thus facilitating fiber disruption and separation. The aim of this review is to describe the mode of action of LPMOs on cellulose fibers towards the isolation of nanostructures, thus highlighting their great potential for the production of nanocellulose as a novel value added product from lignocellulose.

High yielding, one-step mechano-enzymatic hydrolysis of cellulose to cellulose nanocrystals without bulk solvent

Traditional methods of enzymatic hydrolysis of cellulose to cellulose nanocrystals (CNCs) are limited due to the low enzymatic efficiency and large amount of waste liquid. The purpose of this study is to improve the yield and production efficiency of CNCs by enzymatic hydrolysis. A one-step mechano-enzymatic hydrolysis method was developed by utilizing the synergy of wet grinding and enzymatic hydrolysis reaction to efficiently prepare CNCs. Under the optimal reaction conditions, the maximum CNCs yield of 49.3% was achieved with higher thermal stability and crystallinity index of 76.7%. Mechano-enzymatic hydrolysis followed the first order pseudo-kinetics, and fractal kinetics demonstrated that mechanical force of rotation speed affected the fractal dimensions and binding ability between substrate and enzyme. This study provides an alternative method to prepare CNCs, which can significantly avoid the use of bulk water, improve the production efficiency of CNCs and thus lower the production cost.

Nanocellulose Production Using Ionic Liquids with Enzymatic Pretreatment

Nanocellulose has gained increasing attention during the past decade, which is related to its unique properties and wide application. In this paper, nanocellulose samples were produced via hydrolysis with ionic liquids (1-ethyl-3-methylimidazole acetate (EmimOAc) and 1-allyl-3-methylimidazolium chloride (AmimCl)) from microcrystalline celluloses (Avicel and Whatman) subjected to enzymatic pretreatment. The obtained material was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), and thermogravimetric analysis (TG). The results showed that the nanocellulose had a regular and spherical structure with diameters of 30-40 nm and exhibited lower crystallinity and thermal stability than the material obtained after hydrolysis with Trichoderma reesei enzymes. However, the enzyme-pretreated Avicel had a particle size of about 200 nm and a cellulose II structure. A two-step process involving enzyme pretreatment and hydrolysis with ionic liquids resulted in the production of nanocellulose. Moreover, the particle size of nanocellulose and its structure depend on the ionic liquid used.

Effect of Mechanical Treatment of Eucalyptus Pulp on the Production of Nanocrystalline and Microcrystalline Cellulose

This study aimed to assess the effect of mechanical pretreatment on bleached eucalyptus kraft pulp fibers and investigate the influence of reaction time and temperature on the properties and yield of nanocrystalline cellulose (NCC) and microcrystalline cellulose (MCC). Two types of pulps were hydrolyzed, pulp 1 (control, whole fibers) and pulp 2 (mechanically pretreated, disintegrated fibers). NCC and MCC particles were obtained by sulfuric acid hydrolysis (60% w/w) of eucalyptus pulps under different conditions of time (30–120 min) and temperature (45–55 °C). Physical treatment of kraft pulp facilitated acid hydrolysis, resulting in higher NCC yields compared with no pretreatment. The morphologic properties and crystallinity index (CI) of NCC and MCC were little affected by pulp pretreatment. NCC particles obtained from pulps 1 and 2 were needle-shaped, with mean diameters of 6 and 4 nm, mean lengths of 154 and 130 nm, and CI of 74.6 and 76.8%, respectively. MCC particles obtained from pulps 1 and 2 were rod-shaped, with mean diameters of 2.4 and 1.4 µm, mean lengths of 37 and 22 µm, and CI of 73.1 and 74.5%, respectively. Pulps 1 and 2 and their respective NCC and MCC derivatives had a cellulose I crystalline structure.

Cellulose nanocrystals: Pretreatments, preparation strategies, and surface functionalization

Cellulose nanocrystals (CNCs) have attracted great interest from researchers from academic and industrial areas because of their interesting structural features and unique physicochemical properties, such as magnificent mechanical strength, high surface area, and many hydroxyl groups for chemical modification, low density, and biodegradability. CNCs are an outstanding contender for applications in assorted fields comprehensive of, e.g., biomedical, electronic gadgets, water purifications, nanocomposites, membranes. Additionally, a persistent progression is going on in the extraction and surface modification of cellulose nanocrystals to fulfill the expanding need of producers to fabricate cellulose nanocrystals-based materials. In this review, the foundation of nanocellulose that emerged from lignocellulosic biomass and recent development in extraction/preparation of cellulose nanocrystals and different types of cellulose nanocrystal surface modification techniques are summed up. The different sorts of cellulose modification reactions that have been discussed are acetylation, oxidations, esterifications, etherifications, ion-pair formation, hydrogen bonding, silanization, nucleophilic substitution reactions, and so forth. The mechanisms of surface functionalization reactions are also introduced and considered concerning the impact on the reactions. Moreover, the primary association of cellulose and different forms of nanocellulose has likewise been examined for beginners in this field.

Isolation and modification of nano-scale cellulose from organosolv-treated birch through the synergistic activity of LPMO and endoglucanases

Nanocellulose isolation from lignocellulose is a tedious and expensive process with high energy and harsh chemical requirements, primarily due to the recalcitrance of the substrate, which otherwise would have been cost-effective due to its abundance. Replacing the chemical steps with biocatalytic processes offers opportunities to solve this bottleneck to a certain extent due to the enzymes substrate specificity and mild reaction chemistry. In this work, we demonstrate the isolation of sulphate-free nanocellulose from organosolv pretreated birch biomass using different glycosyl-hydrolases, along with accessory oxidative enzymes including a lytic polysaccharide monooxygenase (LPMO). The suggested process produced colloidal nanocellulose suspensions (ζ-potential -19.4 mV) with particles of 7-20 nm diameter, high carboxylate content and improved thermostability (T_o = 301 °C, T_max = 337 °C). Nanocelluloses were subjected to post-modification using LPMOs of different regioselectivity. The sample from chemical route was the least favorable for LPMO to enhance the carboxylate content, while that from the C1-specific LPMO treatment showed the highest increase in carboxylate content.

Plant celluloses, hemicelluloses, lignins, and volatile oils for the synthesis of nanoparticles and nanostructured materials

A huge variety of plants are harvested worldwide and their different constituents can be converted into a broad range of bionanomaterials. In parallel, much research effort in materials science and engineering is focused on the formation of nanoparticles and nanostructured materials originating from agricultural residues. Cellulose (40-50%), hemicellulose (20-40%), and lignin (20-30%) represent major plant ingredients and many techniques have been described that separate the main plant components for the synthesis of nanocelluloses, nano-hemicelluloses, and nanolignins with divergent and controllable properties. The minor components, such as essential oils, could also be used to produce non-toxic metal and metal oxide nanoparticles with high bioavailability, biocompatibility, and/or bioactivity. This review describes the chemical structure, the physical and chemical properties of plant cell constituents, different techniques for the synthesis of nanocelluloses, nanohemicelluloses, and nanolignins from various lignocellulose sources and agricultural residues, and the extraction of volatile oils from plants as well as their use in metal and metal oxide nanoparticle production and emulsion preparation. Furthermore, details about the formation of activated carbon nanomaterials by thermal treatment of lignocellulose materials, a few examples of mineral extraction from agriculture waste for nanoparticle fabrication, and the emerging applications of plant-based nanomaterials in different fields, such as biotechnology and medicine, environment protection, environmental remediation, or energy production and storage, are also included. This review also briefly discusses the recent developments and challenges of obtaining nanomaterials from plant residues, and the issues surrounding toxicity and regulation.

Nanocellulose Production: Exploring the Enzymatic Route and Residues of Pulp and Paper Industry

Increasing environmental and sustainability concerns, caused by current population growth, has promoted a raising utilization of renewable bio-resources for the production of materials and energy. Recently, nanocellulose (NC) has been receiving great attention due to its many attractive features such as non-toxic nature, biocompatibility, and biodegradability, associated with its mechanical properties and those related to its nanoscale, emerging as a promising material in many sectors, namely packaging, regenerative medicine, and electronics, among others. Nanofibers and nanocrystals, derived from cellulose sources, have been mainly produced by mechanical and chemical treatments; however, the use of cellulases to obtain NC attracted much attention due to their environmentally friendly character. This review presents an overview of general concepts in NC production. Especial emphasis is given to enzymatic hydrolysis processes using cellulases and the utilization of pulp and paper industry residues. Integrated process for the production of NC and other high-value products through enzymatic hydrolysis is also approached. Major challenges found in this context are discussed along with its properties, potential application, and future perspectives of the use of enzymatic hydrolysis as a pretreatment in the scale-up of NC production.