Fractionation and cellulase treatment for enhancing the properties of kraft-based dissolving pulp

Construction and Characterization of Fitting Equations for a New Wheat Straw Pulping Method

The pretreatment of pulp with enzymes has been extensively studied in the laboratory. However, due to cost constraints, the application of enzymes in the pulp and paper industry is very limited. In this paper, an environment-friendly and efficient pulping method is proposed as an alternative to traditional pulping and papermaking methods. This new method overcomes the low efficiency and extreme pollution problems associated with traditional pulping methods. In addition, fitting equations for the new pulping method are constructed using data on enzyme treatments, which reflect the effect of enzymes and enable the realization of real-time control of the pulping process. The experimental results show that the efficiency of the pulping and papermaking process can be improved using biological enzymes, and the separation of cellulose can be facilitated using mixed enzymes, which have a better effect than single enzymes.

Enzymatic treatment processes for the production of cellulose nanomaterials: A review

Cellulose nanomaterials have attracted much attention in recent years because of their unique properties. Commercial or semi-commercial production of nanocellulose has been reported in recent years. Mechanical treatments for nanocellulose production are viable but highly energy-intensive. Chemical processes are well reported; however, these chemical processes are not only costly, but also cause environmental concerns and end-use related challenges. This review summarizes recent researches on enzymatic treatment of cellulose fibers for the production of cellulose nanomaterials, with focus on novel enzymatic processes with xylanase and lytic polysaccharide monooxygenases (LPMO) to enhance the efficacy of cellulase. Different enzymes are discussed, including endoglucanase, exoglucanase and xylanase, as well as LPMO, with emphasis on the accessibility and hydrolytic specificity of LPMO enzymes to cellulose fiber structures. LPMO acts in a synergistic way with cellulase to cause significant physical and chemical changes to the cellulose fiber cell-wall structures, which facilitate the nano-fibrillation of the fibers.

Lignocellulose dissociation with biological pretreatment towards the biochemical platform: A review

Lignocellulose utilization has been gaining great attention worldwide due to its abundance, accessibility, renewability and recyclability. Destruction and dissociation of the cross-linked, hierarchical structure within cellulose hemicellulose and lignin is the key procedure during chemical utilization of lignocellulose. Of the pretreatments, biological treatment, which can effectively target the complex structures, is attractive due to its mild reaction conditions and environmentally friendly characteristics. Herein, we report a comprehensive review of the current biological pretreatments for lignocellulose dissociation and their corresponding degradation mechanisms. Firstly, we analyze the layered, hierarchical structure of cell wall, and the cross-linked network between cellulose, hemicellulose and lignin, then highlight that the cracking of β-aryl ether is considered the key to lignin degradation because of its dominant position. Secondly, we explore the effect of biological pretreatments, such as fungi, bacteria, microbial consortium, and enzymes, on substrate structure and degradation efficiency. Additionally, combining biological pretreatment with other methods (chemical methods and catalytic materials) may reduce the time necessary for the whole process, which also help to strengthen the lignocellulose dissociation efficiency. Thirdly, we summarize the related applications of lignocellulose, such as fuel production, chemicals platform, and bio-pulping, which could effectively alleviate the energy pressure through bioconversion into high value-added products. Based on reviewing of current progress of lignocellulose pretreatment, the challenges and future prospects are emphasized. Genetic engineering and other technologies to modify strains or enzymes for improved biotransformation efficiency will be the focus of future research.

Xylanolytic Enzymes in Pulp and Paper Industry: New Technologies and Perspectives

The pulp and paper industry discharges massive amount of wastewater containing hazardous organochlorine compounds released during different processing stages. Therefore, some cost-effective and nonpolluting practices such as enzymatic treatments are required for the potential mitigation of effluents released in the environment. Various xylanolytic enzymes such as xylanases, laccases, cellulases and hemicellulases are used to hydrolyse raw materials in the paper manufacturing industry. These enzymes are used either individually or in combination, which has the efficient potential to be considered for bio-deinking and bio-bleaching components. They are highly dynamic, renewable, and high in specificity for enhancing paper quality. The xylanase act on the xylan and cellulases act on the cellulose fibers, and thus increase the bleaching efficacy of paper. Similarly, hemicellulase enzyme like endo-xylanases, arabinofuranosidase and β-D-xylosidases have been described as functional properties towards the biodegradation of biomass. In contrast, laccase enzymes act as multi-copper oxidoreductases, bleaching the paper by the oxidation and reduction process. Laccases possess low redox potential compared to other enzymes, which need some redox mediators to catalyze. The enzymatic process can be affected by various factors such as pH, temperature, metal ions, incubation periods, etc. These factors can either increase or decrease the efficiency of the enzymes. This review draws attention to the xylanolytic enzyme-based advanced technologies for pulp bleaching in the paper industry.

Dissolving pulp production: Cellulases and xylanases for the enhancement of cellulose accessibility and reactivity

Dissolving pulps are high-grade cellulose pulps that have minimum amount of non-cellulosic impurities. Dissolving pulps are the basic source for the manufacturing of several cellulosic products such as viscose, lyocell, cellulose acetates, cellulose nitrates, carboxymethyl-cellulose, etc. Dissolving pulps are mainly manufactured by pre-hydrolysis kraft and acid sulphite pulping. A high reactivity of dissolving pulps is desirable for its eco-friendly utilization for several purposes. Several approaches including mechanical, chemical, ultrasonic, and enzymatic treatments have been employed for the improvement of pulp reactivity. This review mainly focussed on pulp reactivity improvement through enzymatic approaches. Cellulases and xylanase have been proved effective for the improvement of pulp reactivity of dissolving pulp from different sources. The different combinations of cellulase, xylanase, and mechanical refining have been tested and found more effective rather than the single one.

Applications of enzymatic technologies to the production of high-quality dissolving pulp: A review

Recently, the worldwide production of dissolving pulp has grown rapidly. Enzymatic technologies play an important role in producing high-quality dissolving pulp, due to their green, mild conditions, high specificity and efficiency. In this review, the relevant publications regarding enzyme applications for dissolving pulp are summarized. Cellulase and xylanase are two major enzymes used for this purpose. Cellulase can improve the quality of dissolving pulp, such as improving the reactivity/accessibility, controlling the intrinsic viscosity and adjusting the molecular weight. Xylanase is mainly used to increase the purity of the dissolving pulp and improve the pulp brightness. Furthermore, in order to increase the enzymatic treatment efficiency, the enzymatic technology can be combined with other techniques, including mechanical refining, fiber fractionations, alkali treatment and use of additives. The advantages, disadvantages and practical implications are analyzed. Also, the potential of other enzymes (such as laccase, mannanase) are discussed.

Enhancing the Fock reactivity of dissolving pulp by the combined prerefining and poly dimethyl diallyl ammonium chloride-assisted cellulase treatment

Dissolving pulp is an important source of cellulose raw material, and its key quality parameter is the Fock reactivity for viscose rayon application. Cellulase treatment is an effective method for improving the Fock reactivity of kraft-based dissolving pulp. In this study, a novel process concept of improving the cellulase treatment for this purpose was developed, and it consists of mechanical pre-refining and PDADMAC-assisted cellulase treatment. The hypothesis is based on: 1) opening up the fiber structures to improve the cellulase accessibility by pulp prerefining, 2) the addition of cationic poly DADMAC to the subsequent cellulase stage enhances the cellulase adsorption onto anionic fibers due to favorable electrostatic interactions. The results showed that the Fock reactivity of the resultant pulp from the combined treatment is much higher than that of the control, yet, achieved at a much lower cellulase dosage.

Heteropoly acid catalytic treatment for reactivity enhancement and viscosity control of dissolving pulp

The reactivity enhancement and viscosity control are of practical importance during the manufacture of high-quality cellulose (also known as dissolving pulp). In the study, the concept of using phosphotungstic acid (HPW) for this purpose was demonstrated. The Fock reactivity of resultant pulp increased from 49.1% to 74.1% after the HPW catalytic treatment at a dosage of 86.4 mg HPW/g odp. The improved results can be attributed to the increased fiber accessibility, thanks to the favorable fiber morphologic changes, such as increased pore volume/size, water retention value and specific surface area. HPW can be readily recycled/reused by evaporating method, where maintaining 87.1% catalytic activity after six recycle times. The HPW catalytic treatment concept may provide a green alternative for the manufacture of high-quality dissolving pulp.