Nishi Kant Bhardwaj

A comparative study of the effect of refining on charge of various pulps

This work studied the influence of refining on various pulp properties such as freeness, specific surface area, specific volume, water retention value, surface charge, total charge and tensile index of five different pulps. At a freeness level the wheat straw pulp exhibited higher surface charge and total charge compared to other pulps. The specific surface area, specific volume and water retention value of the pulps increased with increased refining. The total fibre charge as determined by conductometric titrations was not affected by refining. However, the surface charge as determined by titrations with poly-DADMAC increased with refining. The increases in specific surface area of pulps by refining resulted in a higher fibre surface charge and also better fibre-fibre bonding. The linear regression models developed using experimental data were found to be accurate. The comparison of model predicted data and the experimental data showed an excellent agreement between them.

Pretreatment with xylanase and its significance in hemicellulose removal from mixed hardwood kraft pulp as a process step for viscose.

The upturn of viscose fiber market has triggered an augmented dissolving pulp usage over the last decade. Dissolving pulp is feasible to obtain from kraft pulp after two essential steps including hemicellulose removal and subsequent pulp activation. Prerequisite of conversion being hemicellulose reduction can be gently done by using xylanase treatment prior to alkali extraction. Herein, the significance of xylanase treatment and the optimum xylanase dose required in conjunction with subsequent alkali extraction was investigated. An increase in xylanase dose prior to alkali extraction had no significant effect on pentosans while the Fock reactivity and viscosity both improved at the dose of 50AXU/g. Also, alkali extraction without xylanase pretreatment resulted in decreased Fock reactivity, alpha cellulose, brightness and viscosity of paper grade pulp. A moderate dose of xylanase prior to alkali extraction can thus be used to facilitate the hemicellulose removal while simultaneously protecting the native structure of cellulose.

Fabrication of poly (vinyl alcohol)/ovalbumin/cellulose nanocrystals/nanohydroxyapatite based biocomposite scaffolds

ABSTRACT Biocomposite scaffolds composed of PVA, ovalbumin, cellulose nanocrystals, and nanohydroxyapatite were fabricated by freeze-drying method. The results revealed that the different fractions of nanohydroxyapatite and cellulose nanocrystals provide the mechanical strength and stiffness to the desired biocomposite scaffolds. In vitro biomineralization showed the formation of apatite onto the surface of obtained biocomposite scaffolds and increased as amount of nanohydroxyapatite increased. The obtained results suggest that the different combinations of these four biomaterials can be used to fabricate highly porous scaffolds with desired mechanical performance and degradation rate by adjusting ratio for potential use in low load-bearing applications. GRAPHICAL ABSTRACT

Morphological, mechanical, and in vitro cytocompatibility analysis of poly(vinyl alcohol)–silica glass hybrid scaffolds reinforced with cellulose nanocrystals

ABSTRACT Cellulose nanocrystal-reinforced poly(vinyl alcohol)/silica glass hybrid scaffolds were fabricated using the freeze-drying method. In this study, we develop molecular-level-based hybrid scaffolds with possible bioactivity behavior by adding silica sol–gel. The results showed a highly porous structure and a significant improvement in mechanical performance (stiffness) of hybrid scaffolds with an increased content of cellulose nanocrystals followed by the addition of silica-based bioactive glass. In vitro cell study with MC3T3-E1 cells on hybrid scaffolds for 1 and 3 days revealed good cell adhesion and growth. Thus, the obtained hybrid scaffold may be a competitive candidate for bone tissue engineering applications.

Application of Microbial Enzymes in Dissolving Pulp Production

The uprising demand in dissolving pulp, a special chemical pulp, during the last decade has fascinated the researchers to develop a modern biotechnology which could either improve its existing processes or facilitate novel processes of production in eco-friendly manner. These include the use of different microbial enzymes or the microorganisms themselves in various bioprocesses such as biopulping and/or biobleaching of sulphite pulp or bioconversion of kraft pulp to dissolving pulp. The hydrolytic enzymes specifically xylanases and cellulases have been used as the process tools rendering the benefit of eco-friendly and economic bioprocess. Special emphasis is paid to convert kraft pulp, originating from both wood and nonwood, into dissolving pulp by using xylanases and cellulases to selectively reduce hemicelluloses and improve pulp reactivity, respectively. The viscose process being a major consumer of dissolving pulp has drawn more attention. Extensive research work has been conducted to achieve high pulp reactivity as well as accessibility towards solvent and reagent for reducing the carbon disulphide (CS2) consumption in viscose process. Here, the various characteristic properties of dissolving pulp and its end use with various processes, including existing and novel, for its production are reviewed. Microbial enzymes, namely, xylanases and cellulases, for their immense potential as process tools are briefly discussed along with their mode of action.

Bacterial cellulase treatment for enhancing reactivity of pre-hydrolysed kraft dissolving pulp for viscose

To improve the process economy of reactivity improvement, crude cellulase from Bacillus subtilis was employed for the treatment and significant dissolving pulp properties were analyzed. With increase in enzyme dose from 0.25 to 2 U/g o.d. pulp, improvement in Fock reactivity and alkali solubilities (S10 and S18) were observed with simultaneous reduction in viscosity and yield. Fourier transform infrared spectroscopy and scanning electron microscopy were used to observe the molecular level effects on dissolving grade pulp. The most suitable cellulase dose for reactivity improvement with lowering of viscosity was 0.25 U/g o.d. pulp. With increases in enzyme dose, alkali solubilities (S10 and S18) of dissolving pulp showed continuous increment, while alpha-cellulose of pulp showed reduction due to chain scission of long cellulose fiber fraction.

Corrigendum to “Pretreatment with xylanase and its significance in hemicelluloses removal from mixed hardwood kraft pulp as a process step for viscose” [Carbohydr. Polym. 145 (2016) 95–102]

Please cite this article in press as: Kaur, P., et al. Corrigendum to “Pretreatment with xylanase and its significance in hemicelluloses removal from mixed hardwood kraft pulp as a process step for viscose” [Carbohydr. Polym. 145 (2016) 95–102]. Carbohydrate Polymers (2016), http://dx.doi.org/10.1016/j.carbpol.2016.07.047 Which is corrected as: “For differently treated pulps . . .. . .. . . amorphous phase it was found at 2 = 18.72◦, 18.39◦, 18.30◦, 18.17◦ and 18.32◦ respectively Fig. 5).” The authors would like to apologise for any inconvenience caused.