Production of Nanocellulose by Enzymatic Treatment for Application in Polymer Composites

Abstract

In the last few years, the scientific community around the world has devoted a lot of attention to the search for the best methods of obtaining nanocellulose. In this work, nanocellulose was obtained in enzymatic reactions with strictly defined dispersion and structural parameters in order to use it as a filler for polymers. The controlled enzymatic hydrolysis of the polysaccharide was carried out in the presence of cellulolytic enzymes from microscopic fungi—Trichoderma reesei and Aspergillus sp. It has been shown that the efficiency of bioconversion of cellulose material depends on the type of enzymes used. The use of a complex of cellulases obtained from a fungus of the genus Trichoderma turned out to be an effective method of obtaining cellulose of nanometric dimensions with a very low polydispersity. The effect of cellulose enzymatic reactions was assessed using the technique of high-performance liquid chromatography coupled with a refractometric detector, X-ray diffraction, dynamic light scattering and Fourier transform infrared spectroscopy. In the second stage, polypropylene composites with nanometric cellulose were obtained by extrusion and injection. It was found by means of X-ray diffraction, hot stage optical microscopy and differential scanning calorimetry that nanocellulose had a significant effect on the supermolecular structure, nucleation activity and the course of phase transitions of the obtained polymer nanocomposites. Moreover, the obtained nanocomposites are characterized by very good strength properties. This paper describes for the first time that the obtained cellulose nanofillers with defined parameters can be used for the production of polymer composites with a strictly defined polymorphic structure, which in turn may influence future decision making about obtaining materials with controllable properties, e.g., high flexibility, enabling the thermoforming process of packaging.

Nanocellulose from Agricultural Wastes: Products and Applications—A Review

“…One of the most studied area for this polysaccharide (nanocrystals or nanofibers) application is based on reinforcing synthetic polymers (elastomers, thermosets or thermoplastics) using small quantities of fillers (<5% by weight, [84]) to obtain lighter and more resistant-to-corrosion materials. Cellulose nanofibers with defined parameters have be used for the production of polymer composites with a strictly defined polymorphic structure, which may permit obtaining materials with good properties, enabling the thermoforming process of packaging [85,86]. The incorporation of nanocellulose into the polymeric matrix is encouraged by weak (van der Waals forces and hydrogen bondings) and strong (covalent) intermolecular linkages [87], providing materials with suitable elasticity and more tensile strength.…”

Cellulose based Nano-Composites and Applications

“…Cellulose nanocrystals are produced through the splitting or separation of amorphous and crystalline domains of cellulose nanofibrils, with the crystalline region forming cellulose nanocrystals. This is achieved through a process known as acid hydrolysis, whereby the amorphous regions of native cellulose, which are most susceptible to acid attack, are hydrolyzed into solution whereas the crystalline region still remains in a solid form [35] Initially, the feed stock (cellulosic material) or raw cellulose undergoes purification and bleaching to remove all unwanted constituents such as lignin and hemicelluloses. Thereafter, cellulose is treated with a strong acid such as hydrochloric acid or sulfuric acid under carefully controlled conditions.…”

Nanocellulose Production Using Ionic Liquids with Enzymatic Pretreatment

“…Different classes of enzymes have been applied in nanocellulose preparations, including cellulases, xylanases, and lytic polysaccharide monooxygenases [27]. However, cellulases, which are produced by cellulolytic organisms, including fungal species such as Aspergillus, Trichoderma, or Clostridium, are the most commonly used in preparation of nanocellulose [27,28]. It is generally recognized that complete hydrolysis of cellulose to glucose requires a synergistic action of at least two of the three groups into which cellulases are divided, namely endoglucanases, exoglucanases, and cellobiohydrolases [1,29].…”

“…However, for the production of nanocellulose, endoglucanases are of greatest interest due to their action on amorphous cellulose [30]. It should also be emphasized that the efficiency of the enzymatic hydrolysis process depends on the types of cellulolytic enzymes that determine the sizes of nanometric particles, as well as their polydispersion [28]. According to data from the literature, enzymes are used in the extraction of nanometric cellulose, both alone or combined with chemical or mechanical methods [22,27,[31][32][33][34][35][36][37][38].…”