Abstract
Xylanase is commonly applied in pulp and paper industries to ease cost-related and environmental pressures. The effect of xylanase treatment on pulp bleaching is well-established, however, few studies were conducted on the effects of xylanase treatment in pulp yellowing, especially the mechanism of pulp yellowing inhibition by xylanase treatment. In this study, pure xylanase (EC 3.2.1.8) was applied to treat wheat straw chemical pulp (CP) and poplar chemi-thermo-mechanical pulp (CTMP) to determine their effects on pulp brightness and on light- and heat-induced yellowing. The xylanase treatment decreased the post-color number of the pulps during light- and heat-induced yellowing. However, differences were observed in the yellowing inhibition between the wheat straw CP and poplar CTMP. The changes in chemical components of pulps after the xylanase treatment, for example, lignin, hemicellulose, and HexA contents, and analysis of UV–vis absorption spectra and Fourier transform infrared-attenuated total reflectance spectrum were used to explore the pulp yellowing inhibition causes by the xylanase treatment.
Highlights
The world’s total production of paper and paperboard reached approximately 400 million tons in 2012, and the global demand for paper and paperboard for packaging purposes has increased by 75% in the last five years[1]
We investigated the effects of xylanase treatment on pulp light- and heat-induced yellowing and its inhibition yellowing mechanism
The decrease in hemicellulose content of wheat straw chemical pulp (CP) was higher than that of poplar chemi-thermo-mechanical pulp (CTMP) after xylanase treatment under the same treatment conditions. This result is probably because wheat straw CP contained more hemicellulose compared with poplar CTMP and xylan is a primary hemicellulose sugar in wheat straw CP
Summary
The world’s total production of paper and paperboard reached approximately 400 million tons in 2012, and the global demand for paper and paperboard for packaging purposes has increased by 75% in the last five years[1]. Fluorescent whitening agents are another type of substance that can be applied to slow down pulp yellowing[20], and studies have shown that chemical modification and paper coating are effective methods of inhibiting yellowing[12]. Most of these methods are not appropriate in practice because www.nature.com/scientificreports/. Ramos et al.[21], for example, applied crude ligninolytic enzymes, which possess laccase, lignin peroxidase, and manganese peroxidase to sugar cane bagasse, to enhance pulping and paper properties They found that the brightness of enzyme-treated pulps increased by 2% compared with the control
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