Paper industry "enzyme" good future

Traditional industrial chemicals are heavily consumed

The pulping section in the paper industry is to destroy the plant cell wall by mechanical or chemical methods to remove the lignin and hemicellulose wrapped with cellulose in lignocellulosic raw materials, so that cellulose can be separated and used. As a result, the papermaking and pulping section consumes a lot of energy and chemicals, and may damage the cellulose.

In the pulp and paper industry of wood fiber as raw materials, for example, in order to dissolve and remove lignin and hemicellulose and release cellulose, chemical pulping requires a large number of chemicals such as sodium hydroxide, sodium sulfide and sodium sulfite in the process of wood chip pulping. The pulping and deinking processes using waste paper as raw materials mainly use sodium hydroxide, sodium silicate and surfactants. In the pulping bleaching section, chlorine compounds, hydrogen peroxide, ozone and other oxidants are mainly used.

In order to improve the papermaking process and pulp performance, the papermaking process also uses a variety of chemical additives, reinforcing agents, sizing additives and coating adhesives and other chemicals, making the pulp and paper industry become one of the main light industries for chemical use and emission.

Enzymes help green development

With the continuous development of industrial biotechnology, new enzyme molecules have been gradually excavated, and the level of efficient enzyme fermentation production and application has been continuously improved. How to improve the application efficiency of enzyme preparations in the pulp and paper industry and reduce production costs has become a hot spot of concern for scientists and industry.

In the past ten years, through the collaboration of bioscientists and pulp and paper engineering personnel, enzyme preparations have been applied in pulp and paper making, and remarkable results have been achieved in reducing energy consumption and the use of harmful substances in biological pulping.

Biological pulping refers to the pretreatment of wood fiber by enzyme producing microorganisms or enzyme preparations, destroying the structure of lignin or hemicellulose, promoting its shedding rate in the mechanical or chemical pulping process, which is conducive to the separation of cellulose, while reducing the consumption of energy and alkali, shortening the pulping time, and improving the quality of pulping.

For example, white rot bacteria have been widely used in the research of biological pulping. White rot bacteria are rich in laccase, which can effectively decompose lignin in wood fibers. More importantly, as a filamentous fungus of basidiomycetes, white rot bacteria can penetrate wood raw materials and release extracellular enzymes in mixed culture pretreatment of wood and other raw materials to promote lignin decomposition.

With the enhancement of people's environmental awareness, in order to reduce the impact of chlorine emissions on the environment in the paper industry, the development of non-chlorine bleaching process is also the focus of the pulp and paper industry, pulp bioenzyme bleaching is one of the non-chlorine bleaching ways with development prospects. Xylanase and laccase are the main enzymes used for biobleaching in the paper industry.

In addition, there are some fat-soluble extracts in the pulping and papermaking process of wood or non-wood annual herbal fiber raw materials. After these substances fall off, they are not soluble in water and are removed. If they are deposited in the pulp and brought into the paper, they will form "paper disease".

The use of color-changing bacteria, white rot bacteria and other microorganisms to pretreat wood chips can obviously achieve the purpose of resin control. In contrast, enzyme preparation is mainly used to remove fat soluble extracts from pulp, and the use of enzyme preparation for resin control has the characteristics of short action time and good specificity.

Not only that, the use of enzyme preparations for waste paper deinking applications can also reduce wastewater discharge, save water and energy consumption.

In addition, the enzyme can also improve the properties of papermaking fiber. In the pulping process, there is a refining section, that is, the dredging and finishing of pulping cellulose, the main purpose is to improve the papermaking and strength of cellulose, cut off too long fibers to improve the uniformity of paper, and improve the absorption rate, porosity and whiteness of paper. The traditional method is mainly through mechanical action or the action of chemical substances to achieve the required goal, but the use of microbial enzymes for biological modification of pulp fiber is beneficial to save energy and reduce the destruction of chemical agents on fiber.

Continue to promote the application of biotechnology

In the paper industry, there have been cases of industrial-scale use of papermaking enzymes, including cellulase, xylanase, pectinase, manganese peroxidase and laccase, in the sections of crude pulp washing, mechanical pulp bleaching, waste paper beating and deinking for chemical pulping.