Application and research progress of biological enzymes in pulp and paper making process

1. The importance of biotechnology for pulp and paper making

The pulp and paper industry uses plant fibers as raw materials in the production process, such as wood and non-wood. These raw materials are rich in cellulose, hemicellulose, resin and pectin and other organic, inorganic extracts and minerals, etc., so in the pulping and papermaking often need to use physical or chemical means to remove or retain lignin and other waste cellulose, resulting in biotechnology and pulping and papermaking process between inextricably linked. In fact, the application of biotechnology in pulping and papermaking can be traced back to 105 AD, but it was not until the 1960s that pulping and papermaking gradually entered the era of industrialization, coupled with the continuous development and improvement of bioengineering, genetic engineering and enzyme engineering technology, the industrialization of biological enzymes has brought great opportunities to the development of pulping and papermaking industry. And gradually penetrate into the various processes of pulp and paper, to a large extent to promote the rapid development of the paper industry.

2, the application of biological enzymes in the process of pulping and papermaking

2.1 Biological pulping

The so-called biological pulping is actually the use of biological enzymes to degrade raw materials, and further combined with mechanical and chemical means to further separate the fiber raw materials, this process is called biological pulping. In general, the biological enzymes used in different raw materials are not the same. For example, phloem fibers contain a lot of glia, so it is necessary to select pectinase to decompose the glia and release cellulose. Straw pulp and wood pulp are rich in lignin, so it is necessary to choose a combination of lignin degradation, chemical pulping and mechanical pulping to complete the pulping work [1]. It can be seen that the basic process of biological pulping is: wood chip - enzyme treatment - chemical or mechanical pulping, general chemical pulping or biological pulping advantages are lower energy consumption, low alkali consumption, light environmental pressure and mild performance.

2.2 Biological Bleaching

Hemicellulase and lignin-degrading enzymes are mainly used in pulping bleaching, among which hemicellulase includes xylanase and polynose-degrading enzyme. The purpose of biological bleaching is to use as little chemical bleach as possible to improve the performance of pulping, thereby reducing the pollution caused by bleach. In general, xylitase can effectively improve the whiteness of pulping and reduce the amount of bleach and waste water pollution in pulping bleaching pretreatment, while not adversely affecting the viscosity of the pulp and the strength of the paper. Compared with the bleaching process using hydrogen dioxide or hydrogen peroxide, the production cost can be significantly reduced. However, in terms of its mechanism, xylosin only plays a role in the bleaching process, and can not directly replace the chemical bleaching agent. The development of xylosin-assisted bleaching is actually an enzyme that is stable and can show biological activity under high temperature resistance and alkaline environment. The main reason is that the temperature of sulfate can reach 95℃ after cooking, and its PH value can reach or even exceed 13. Under such conditions, dellignification basically does not change. Therefore, in order to promote the enzyme can be directly into the pulp after cooking or washing without reducing the temperature and PH value of the pulp, it is necessary to use the high temperature resistance and alkaline ability of xylose enzyme, so xylose enzyme is a promising biological agent.

2.3 Enzymatic beating

The role of enzymes is to achieve the goal of reducing the energy consumption of beating with the help of cellulose modification. At present, the biological enzymes widely used in the process of pulp and paper are: pectinase, cellulase, xylose enzyme, mannanase, laccase and arabinose hydrolase.

Taking cellulase as an example, the application of cellulase in pulp and paper is often the first to act on the amorphous region of cellulose, but the crystallization region is not very sensitive to cellulase. The use of cellulase, hemicellulase and xylosamase to carry out pre-treatment before beating can effectively reduce energy consumption and steam consumption, and achieve the goal of improving paper performance [2].

At present, the price of pure enzymes is slightly high, so it is necessary to find the right adjuvant to improve the efficiency of enzyme use and achieve the goal of reducing energy consumption. However, if the correct use of enzyme treatment in the pulping and papermaking process can not only change the performance of the slurry, but also ensure the normal operation of the paper machine is a major research focus at present.

2.4 Enzymatic deinking

Traditional chemical deinking techniques can no longer meet the requirements of laser printing or copying of office waste paper, and may even cause environmental pollution. The deinking technology using biological enzyme method is gradually mature, and has been tested in laboratory and factory. It is an effective and widely applicable deinking method. At present, the enzymes commonly used in waste paper deinking mainly include cellulase, hemicellulase, esterase, amylase, pectinase and lignin degrading enzyme. Among them, hemicellulase and cellulase are the most used [3].