The use of environment friendly processes is becoming more popular in the pulp and paper industry and therefore biotechnological processes are coming to the forefront of research. Biotechnology is defined as the use of biological organisms/ systems and processes for practical or commercial purposes. In this broad sense, biotechnology encompasses a diverse array of activities including fermentation, immobilized cell and enzyme technology, cell and tissue culture and monoclonal antibody techniques; although in recent years, the term has been increasingly identified with techniques for genetic transfer and DNA manipulation, namely genetic engineering. The attractiveness of biotechnology lies in its potential to provide processes/ products where non-biological processes are impractical, to increase specificity in reactions, to provide less environmentally deleterious processes [1], to save energy [2], and by virtue of the foregoing, to decrease cost. The raw material in forest-based industries is wood and its components. Thus, possibilities for employing biotechnology in these industries are numerous as one of nature’s most important biological processes is the degradation of lignocellulosic materials to carbon dioxide, water and humic substances. In fact, biotechnology has been used in the paper industry for quite some time. Wastewater treatment systems for removal of oxygen-demanding substances and suspended solids, fermentation of sulphite liquors and preparation of starch for paper sizing have long been part of the industry. Improvement in fibre supply by selection of superior trees is still being carried out by forest product companies. Even the control of slime and deposits on paper machines can be considered as an aspect of biotechnology. However, during last few years, biotechnologists have sought specific applications for microorganisms/ enzymes in the pulp and paper industry. This article reviews the past success and future possibilities for biotechnology in the pulp and paper industry.

Biotechnical methods for degradation of pitch have found application in sulphite and TMP mills. Treatment of wood chips in the chip piles with specific resin degrading fungi is one method and another method is to use lipases. Lipases have been used in mill operations to control pitch build up in the white water systems. Different lipases have been used for removal of pitch. Few commercial preparations of lipases for pitch removal are available. The enzymatic pitch control method using lipase was put into practice in a large-scale papermaking process as a routine operation in the early 1990s and was the first case in the world in which an enzyme was put into practice in a large-scale papermaking process [chapter 2 of reference 1]. Lipases have also found a market for deinking applications in cases where the inks contain vegetable oils in their formulations.

Polymers used in laser and xerographic printing have made conventional deinking methods inadequate for recycling to produce high quality paper. Recycling mills are, therefore, increasing dependence upon mechanical devices for breaking down the large, non-impact ink particles to be able to remove them by flotation or washing. These intensive mechanical forces are energy demanding and shorten the fibers decreasing freeness and strength of the paper formed from these fibres. Mixtures of enzymes, mostly cellulases, have therefore been implemented to substitute for chemical deinking of such furnishes. Other furnishes, such as old newsprint (ONP) and old magazine (OMP) are also successfully deinked using mixture of enzymes. Using the so-called Enzynk process, developed at the University of Georgia, it was found that all kinds of recycled paper could be successfully deinked [6]. Some type of furnishes need a large variety of enzymes, others less multiple enzyme components. The company Enzymatic Deinking Technologies (EDT) with offices and laboratories in Norcross near Atlanta, Georgia was founded in 1994. The company has commercialized the enzymatic deinking technology in pulp and paper mills in United States, Europe and Asia and the market for this technique seems to be growing very fast. At present, enzymatic deinking is one of the most promising and viable biotechnologies in the pulp and paper industry. Enzymatic deinking has the capability to reduce the dirt count and stickies and to increase freeness of the pulp to a much greater extent as compared to conventional chemical pulping.

The pulp and paper industry has invested enormous amounts of work and money to abandon at least molecular chlorine and to develop more environmentally benign bleaching processes. Oxygen based chemicals such as O2, O3 or H2O2 in combination with enzymes can be employed for bleaching of pulp and the use of these enzymes in these processes is practically a hot area of research (Table 1). As expected, the phenol oxidase, laccase, manganese peroxidase (MnP) and lignin peroxidase (LiP) are possible enzyme candidates in pulp bleaching processes. Of these, laccase combined with redox mediators is probably the most interesting and it became clear in the recent 8th International Conference on Biotechnology in Pulp & Paper Industry that a race is on involving laboratories in several countries to develop a bleaching stage using laccase plus redox mediators into commercialization [7].

One biotechnology-based process close to commercialization is biopulping. For pulp and paper production, wood chips are stored in chip piles for various lengths of time depending on their future fate. While fresh chips are prepared for kraft pulping, somewhat larger storage times are normally required for chips aimed for sulphite or mechanical pulping. Delignification of chips prior to further processing is desirable both in chemical or mechanical pulping for savings of energy, chemicals, treatment time etc. The delignification is particularly desirable in production of mechanical pulp since it is very energy demanding process. To obtain specific lignin degrading fungi, researchers at the Swedish Pulp and Paper Research Institute in Stockholm directed considerable efforts towards developing cellulase less mutants of white-rot fungus Phanerochaete chrysosporium. However, a more thorough investigation on the feasibility of biomechanical pulping was started in 1987 at the Forest Products Laboratory (FPL) in Madison, Wisconsin. A comprehensive screening program was initiated to select fast-growing white-rot fungi able to selectively remove lignin from wood. Cereporiopsis subvermispora was found to be the best suited for this purpose and has been used in large-scale outdoor delignification of a 50 metric ton chip pile at FPL. In this test about 30% energy was saved and the quality of the paper from the pretreated chips was better than that from the non-pretreated chips [8]. Efforts are being made to commercialize the process. Fungal treatment for kraft pulping of eucalyptus has been recently studied, the results of which show promise for an improved process [9]. Fungal treatment reduced the pitch content in the wood chips and during kraft pulping, reduced the active alkali requirement upto 18%, reduced the total cooking time by upto 33% or reduced the sulphidity requirement of the white  liquor by upto 30%. The quality of the resultant biopulp was better than that of the control. The bleached pulps were easier to refine than the reference pulp.

Improvement of pulp drainage with enzymes (mixture of cellulase and xylanase enzyme) is practiced routinely at mill scale. Several commercial enzymes are available which improve the drainage of secondary fibres. Ciba-Geigy and its partner Genencor have conducted more than 100 plant scale trials. The outcome is several regular customers worldwide. Cellulase and hemicellulase enzymes are also found to reduce energy requirement during refining of chemical and mechanical pulps. At the moment, the process is not economically viable. However, with rising power cost and a possible reduction in enzyme cost in the near future, the process seems to have great potential. Mills, that are currently throughput limited because of refiner power limits, may assign substantial value to the removal of bottlenecks provided by enzymatic treatment.

Pectinases and hemicellulase enzymes are found to reduce energy requirement as much as 80% during debarking. One of the major difficulties with enzymatic debarking is the poor infiltration of enzymes in the cambium of whole logs. Pectinase and xylanase have been also used in processing plant fibre sources such as flax and hemp. At present, the fibre liberation is affected by retting. Replacement of slow natural retting by treatment with artificial mixture of enzymes could become a new fibre liberation technology. A patent of disclosure from Honshu Paper Co. described the use of commercial cellulases to enhance the flexibility of hardwood vessels [10]. Enzyme treatment reduced vessel picking by 85%. At the same time, smoothness and tensile strength increased and drainage time also increased. A novel enzyme formulation, Shivex, which is basically a xylanase enzyme, can be used to increase the efficiency of shive removal by bleaching. By treating brown stock with Shivex, mills can increase the degree of shive removal in the subsequent bleaching by 50%. At a given bleached brightness, Shivex treatment results in a lower shive count. Enzyme treatment, therefore, helps to remove shives from the pulp beyond the associated gain in the brightness. Removal of shives and ease of pulp bleaching by the use of enzymes also help in reducing the energy requirement.