Forming Nanospherical Cellulose Containers

An enzymatic hydrolysis-based platform technology for the efficient high-yield production of cellulose nanospheres

This study evaluates the feasibility of using enzymatic technology to produce novel nanostructures of cellulose nanomaterials, specifically cellulose nanospheres (CNS), through enzymatic hydrolysis with endoglucanase and xylanase of pre-treated cellulose fibers. A statistical experimental design facilitated a comprehensive understanding of the process parameters, which enabled high yields of up to 82.7 %, while maintaining a uniform diameter of 54 nm and slightly improved crystallinity and thermal stability. Atomic force microscopy analyses revealed a distinct CNS formation mechanism, where initial fragmentation of rod-like nanoparticles and subsequent self-assembly of shorter rod-shaped nanoparticles led to CNS formation. Additionally, adjustments in process parameters allowed precise control over the CNS diameter, ranging from 20 to 100 nm, highlighting the potential for customization in high-performance applications. Furthermore, this study demonstrates how the process framework, originally developed for cellulose nanocrystals (CNC) production, was successfully adapted and optimized for CNS production, ensuring scalability and efficiency. In conclusion, this study emphasizes the versatility and efficiency of the enzyme-based platform for producing high-quality CNS, providing valuable insights into energy consumption for large-scale economic and environmental assessments.

Upcycling Food By-products: Characteristics and Applications of Nanocellulose

Rising global food prices and the increasing prevalence of food insecurity highlight the imprudence of food waste and the inefficiencies of the current food system. Upcycling food by-products holds significant potential for mitigating food loss and waste within the food supply chain. Food by-products can be utilized to extract nanocellulose, a material that has obtained substantial attention recently due to its renewability, biocompatibility, bioavailability, and a multitude of remarkable properties. Cellulose nanomaterials have been the subject of extensive research and have shown promise across a wide array of applications, including the food industry. Notably, nanocellulose possesses unique attributes such as a surface area, aspect ratio, rheological behavior, water absorption capabilities, crystallinity, surface modification, as well as low possibilities of cytotoxicity and genotoxicity. These qualities make nanocellulose suitable for diverse applications spanning the realms of food production, biomedicine, packaging, and beyond. This review aims to provide an overview of the outcomes and potential applications of cellulose nanomaterials derived from food by-products. Nanocellulose can be produced through both top-down and bottom-up approaches, yielding various types of nanocellulose. Each of these variants possesses distinctive characteristics that have the potential to significantly enhance multiple sectors within the commercial market.

Controlling the nanocellulose morphology by preparation conditions

Nanocellulose (NC) is the desired building block for novel biomaterials. The morphology of NC is one of the core parameters impacting the functionality and property of engineered functional materials. This work aims to reveal the relationship between the product morphology and sulfuric acid hydrolysis conditions (including acid concentration, temperature and time), and to realize morphological regulation of obtained NC. Three representative products were obtained from microcrystalline cellulose via sulfuric acid hydrolysis, which are cellulose nanocrystals with broad size distribution (W-CNC, 383.9 ± 131.7 nm in length, 6 ± 2.1 nm in height) obtained by 61 % H2SO4, 55 °C and 90 min, cellulose nanospheres (CNS, 61.3 ± 15.9 nm in diameter) obtained by 64 % H2SO4, 35 °C and 75 min, and CNC with narrow size distribution (N-CNC, 276.1 ± 28.7 nm in length, 4.1 ± 0.6 nm in height), obtained by 64 % H2SO4, 45 °C and 45 min. The results showed that the crystallographic form of W-CNC and N-CNC are cellulose I, while cellulose I and II coexist in CNS. Only W-CNC and N-CNC can form chiral nematic structures through evaporation-induced self-assembly strategy and reflected light with specific wavelengths. In addition, the formation mechanism of CNS with cellulose I/II was proposed, which provided a better understanding of NC morphology regulation.

Cellulose nanosphere: Preparation and applications of the novel nanocellulose

Over the past few years, cellulose nanosphere (CNS) has gained growing attention and rapid development. As a new type of nanocellulose materials, CNS can be prepared from native cellulose by using methods which have been adopted extensively to prepare the well-known nanocelluloses, i.e., cellulose nanofiber and cellulose nanocrystal. The particular interest is that the regenerated cellulose and mercerized cellulose can also be used as important feedstocks to produce CNS. In this review, the preparation methods of CNS are described and discussed, via both top-down processes, including chemical, mechanical, and enzymolysis ones, and bottom-up processes by using various cellulose I and II starting materials. This review also highlights the researches relative to cellulose composite nanospheres, and summarizes the applications of spherical cellulose-based nanoparticles. Finally, the future challenges and opportunities of CNS are prospected in this work.

Preparation of cellulose nanospheres via combining ZnCl2·3H2O pretreatment and p-toluenesulfonic hydrolysis as a two-step method

Spherical nanocelluloses, also known as cellulose nanospheres (CNS), have controllable morphology and have shown advantages as green template material, emulsion stabilizer. Herein, CNS were prepared via a new two-step method, first pretreatment of microcrystalline cellulose (MCC) using ZnCl₂·3H₂O and then acid hydrolysis of regenerated cellulose (RC) via p-toluenesulfonic acid (p-TsOH). The shape, size, crystallinity of MCC were changed, and nubbly RC with smallest size (942 nm) was obtained after 2 h pretreatment by ZnCl₂·3H₂O. CNS with high 61.3% yield were produced after acid hydrolysis (67 wt% p-TsOH) of RC at 80 °C, 6 h. The analysis of Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM) showed that CNS had an average diameter of 347 nm. CNS were present in precipitate after high-speed centrifugation, due to the high Zeta potential of -12 mV and large size. The structure of CNS was tested by Fourier Transfer Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Nuclear Magnetic Resonance (NMR), CNS had high crystallinity (cellulose II) of 61%. Thermal Gravimetric Analysis (TGA) indicated that CNS had high thermal stability (T_onset 303.3 °C, T_max 332 °C). CNS showed poor re-dispersibility in water/ethanol/THF, 1 wt% CNS could be dissolved in ZnCl₂·3H₂O. 7.37% rod-like CNC were obtained after 6 h hydrolysis. FTIR proved that p-TsOH was recovered by re-crystallization. This study provided a novel, sustainable two-step method for the preparation of spherical CNS.

Solar-Energy Driven Simultaneous Saccharification and Fermentation of Starch to Bioethanol for Fuel-Cell Applications

A solar reactor was designed to perform the conversion of starch to ethanol in a single step. An aqueous starch solution (5 wt %) was fed into the reactor bed charged with Baker's yeast (Saccharomyces cerevisiae) and amylase, resulting in approximately 2.5 wt % ethanol collected daily (ca. 25 mL day(-1) ). A significant amount of ethanol (38 g) was collected over 63 days, corresponding to 84 % of the theoretical yield. The production of ethanol without additional energy input highlights the significance of this new process. The ethanol produced was also demonstrated as a potential fuel for direct ethanol fuel cells. Additionally, the secondary metabolite glycerol was fully reduced to a value-added product 1,3-propanediol, which is the first example of a fungal strain (Baker's yeast) converting glycerol in situ to 1,3-propanediol.