A Publication on World Pulp, Paper & Allied Industry

October-December' 2001

TECHNOLOGY

   

Status of Biotechnology in Pulp and Paper Industry
by Dr. Pratima Bajpai* and Dr. Pramod K. Bajpai**

 


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.

HISTORICAL PERSPECTIVE
At the time, when biotechnology was developed for the pulp and paper industry i.e. in the mid 70’s, our knowledge about the enzyme mechanisms involved in the degradation of wood and its component was in its infancy. The suggestion, at that time, to use enzymes in pulp and papermaking seemed out of reach. Production of the required enzyme quantities at a price that would have been close to economic feasibility was impossible. However, since then enormous progress has been made in the biosciences in general i.e. in genetics, molecular biology, biochemistry and microbiology. This has allowed for production of enzymes at economically feasible process, which has made them technically interesting for the industry. Enzymes from alkaliphilic and thermophilic microorganisms can now be cloned into efficient production systems and enzymes for bleaching, enzymatic deinking and other papermaking processes can be produced at costs we could hardly envision 10 years ago. Microorganisms can now be genetically changed to make them ideal for specific purposes and enzyme can be designed to better catalyze industrially important reactions. The massive amount of efforts devoted over the past few decades to a better understanding of the enzymes produced by wood degrading microorganisms for conversion and degradation of lignin, cellulose and hemicellulose have provided a fresh base for successful development of biotechnology in pulp and paper industry.
DEVELOPMENTS

Due to above advances, the current state of the art of biotechnology in pulp and paper industry has improved tremendously over the last decade and several new biotechnology markets have been developed. One such development is the use of xylanase in bleaching of kraft pulp. This technology has been successfully transferred to full industrial scale in just a few years. The use of xylanase degrading enzymes to aid in the bleaching of chemical pulp was introduced by Viikari et al. [3]. Xylanases are indirect tools for lignin removal. There are many different hypotheses for how xylanases act and aid in pulp bleaching. A thorough discussion of these hypotheses and theories has been published [4]. This technology is now in use at several mills worldwide. Use of xylanase enzyme can sometimes reduce chemical bleaching costs by upto 20%. For chlorine based bleaching technologies, xylanase pretreatment of kraft pulps has also been shown to reduce the AOX discharges by 5-20% depending upon wood furnish and mill pulping conditions. The use of a xylanase stage into commercial TCF bleaching operations has also been successfully implemented. One such example is the Enzone process, which bleaches hardwood pulp to full brightness in the sequence OXZP and softwood pulp in the sequence OXEPZP [5]. The xylanase stage contributes to the high brightness which, after the full sequence is 5-8% ISO higher as compared to when the xylanase stage is not used.

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.

Table 1: Enzymes investigated for bleaching of wood pulp

Enzymes Reaction catalyzed
Xylanase Degradation of xylan
Laccase plus redox mediators Oxidation/ polymerization of lignin
Manganese Peroxidase (MnP) Oxidation/ polymerization of lignin
Lignin Peroxidase (LiP) Depolymerization/ repolymerization of lignin
Cellobiose Dehydrogenase (CDH) Reduction of quinones, phenoxy and cation radicals

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.

PRESENT STATUS
 

Table 2: Biotechnology in pulp & paper industry: Current status

S. No.

Process

Status

1. Biological depithing of raw material Commercial
2. Biological pitch removal from wood chips Commercial
3. Enzymatic pitch removal from pulp Commercial
4. Xylanases for pulp bleaching Commercial
5. Improvement of pulp drainage by enzymes Commercial
6. Enzymatic deinking Commercial
7. Production of dissolving pulp using xylanase enzyme Commercial
8. Biofiltration for control of odorous emissions Commercial
9. Improving beatability of pulp with enzymes Commercial
10. Pulp bleaching with lignin oxidizing enzymes Pilot scale
11. Biopulping - mechanical/ chemical Pilot scale
12 De-chlorination and de-toxification of bleach effluent Pilot scale
13. Tree improvement Pilot scale
14. Enzymatic debarking Lab. scale
15. Enzymatic retting of flax fibres Lab. scale

Table 2 presents the current developmental stages of various biotechnological approaches for use in the pulp and paper industry. While many applications are still in the research and development stage, several new applications have found their way into the mill in an unprecedently short period of time. In addition, some of these new developments in biotechnology, if successful, could have a profound impact on the future technology of the pulp and paper manufacturing process.

INDIA SCENARIO
 

The commercial application of biotechnology in pulp and paper in India started with the modification of starch for surface sizing of paper. Thapar Centre for Industrial R&D (TCIRD), Patiala carried the developmental work in the 1980s and the process technology is in use in few paper mills since 1992. A similar process of enzymatic modification of starch was also developed by TCIRD for lamination of paperboards, which was brought to the mills in mid 1990s.

The second application of biotech process in Indian pulp and paper industry is xylanase pre-bleaching of pulp. Extensive R&D work on enzymatic prebleaching of pulp from Indian raw materials and manufactured according to pulping and bleaching processes prevalent in India, was done by TCIRD in early 1990s [11-16]. The first ever mill trial on xylanase pre-bleaching in India was conducted in a pulp and paper mill of Ballarpur Industries Ltd. (BILT) in 1992 using acidic xylanase enzyme, produced by M/s Biocon India Pvt. Ltd. Subsequently, several other mill trials were organized in different mills using different types of raw materials and practicing different pulping and bleaching processes, using xylanase enzymes of different qualities (including alkaline and thermotolerant ones). Due to pressure on reducing organochlorine compounds (AOX) in the effluents [17], more and more pulp mills are getting interested in this process and have also started taking mill trials. Century Pulp and Paper [18], Grasim, Central Pulp and Paper Mills, Star Paper Mills, Shreyans Papers and Varinder Agro Paper Mills

Papers and Varinder Agro Paper Mills are worth mentioning. First ever process on the use of xylanase enzyme for the production of high quality dissolving pulp has been developed at TCIRD [19]. By this process, a pulp of better optical properties and reactivity is obtained which also results in higher viscose yield. The process has been transferred to a pulp mill and an Indian patent is pending for the same.

Now, the thermostable alkaline xylanase enzymes are available in India from M/s Novozyme South Asia Pvt. Ltd., Biocon India Pvt. Ltd. (in collaboration with Rohm Enzyme Oy, Finland), Advance Biochemicals Ltd. (in collaboration with BIL, Australia). Earlier Esvin Biotech has also tried to produce xylanase enzyme, in collaboration with BIL-Australia, for pre-bleaching of pulp, which could not see the light of the day. Recently, M/s J.K. Pharma has also started promoting alkaline xylanase enzyme and M/s Khandelwal Laboratories Ltd. is scaling up the xylanase production with partial financial support from Depart of Scientific and Industrial Research (DSIR), Ministry of Industries, Government of India.

Although R&D work on isolation and screening of microbial cultures, capable of producing low molecular weight xylanase enzyme, was done at National Chemical Laboratory Pune in early 1990s, further progress could not take place. Lately, IIT Delhi, Birla Institute of Scientific and Industrial Research Jaipur and few other research and academic institutions have started working on culture development for the production of alkaline thermotolerant xylanase enzymes. A national research laboratory - Central Pulp and Paper Research Institute (CPPRI) and a premier educational institution in the country - Institute of Paper Technology (IPT) have also initiated R&D on xylanase enzyme pre-bleaching of pulp.

R&D works on improving the drainabilty and refining of pulp (virgin as well as recycled) using enzymes have been carried out at TCIRD [20,21]. These processes are still to be commercialized in India for the want of their cost effectiveness. R&D on enzymatic deinking of recycled paper has been initiated at TCIRD [22]. Efforts are on at TCIRD and few other organizations on deinking of mixed office waste and other waste papers.

An R&D project on the development of lignin oxidizing enzymes and its use in delignification of brown stock has been started recently at TCIRD with the financial supports from Department of Science & Technology (DST), Government of India and Ballarpur Industries Ltd.

The laboratory work on bio-pulping of Indian raw materials was initiated in 1995 at TCIRD, Patiala in collaboration with Forest Products Laboratory, Madison, Wisconsin (USA)/ Bio-pulping International Inc. (USA). A technically sound process has been developed for biokraft pulping of eucalyptus [9], for which a world patent under PCT was applied in the year 1998 and subsequently to several countries including India and USA. Now, the efforts are on to commercialize the process. Recently, Indian Agro Paper Mills Association (IAPMA) has shown interest on bio-chemical pulping of agri-residues. Based on the encouraging laboratory results with bagasse and wheat straw at TCIRD, further R&D work has been done with wheat straw. Now, IAPMA and TCIRD are arranging for the pilot scale study at an agro paper mill.

REFERENCES

 

  1. Bajpai, P., Bajpai, P.K. and Kondo R. (1999) Biotechnology for Environmental Protection in Pulp and Paper Industry, Springer-Verlag, Germany.

  2. Bajpai, P. and Bajpai, P.K. (1998) Biotechnology in Pulp and Paper Industry: a Route to Energy Conservation, PIRA International, U.K.

  3. Viikari, L., Ranua, M., Kantelinen, A., Sundquist, J. and Linko. M (1986) Proc. 3rd Intl. Conference on Biotechnology in the Pulp and Paper Industry, Stockholm, Sweden, p. 67.

  4. Suurnakki, A., Tenkanen, M., Buchert, J. and Viikari, L. (1997) Advances in Biochemical Engineering/ Biotechnology Vol. 57 (edited by K.-E. Eriksson, Springer-Verlag, Germany), p. 261.

  5. Young, J.D. (1994) Pulp Pap., Nov. 1994, 81.

  6. Knudsen, O, Young, J.D. and Yang, J.L. (1998) Proc. 7th Intl. Conference on Biotechnology in the Pulp and Paper Industry, Vancouver, Canada, p. A-17.

  7. Call, H.-P. (2001) Proc. 8th Intl. Conference on Biotechnology in the Pulp and Paper Industry, Helsinki, Finland, p. 68.

  8. Akhtar, M., Blanchette, R.A. and Kirk, T.K. (1997) Advances in Biochemical Engineering/ Biotechnology Vol. 57 (edited by K.-E. Eriksson, Springer-Verlag, Germany), p. 159.

  9. Bajpai, P., Bajpai, P.K., Akhtar, M. and Jauhari, M.B. (2001) J. Pulp & Paper Science, 27(7), 235.

  10. Jeffries, T., Patel, R.N., Sykes, M.S. and Klungness, J.H. (1992) Proc. Mater. Res. Soc. Symp. 266, 277.

  11. Bajpai, P. and Bajpai, P.K. (1992) Process Biochemistry. 27(6), 319.

  12. Bajpai, P., Bhardwaj, N.K., Maheshwari, S. and Bajpai, P.K. (1993) Appita 46(4), 274.

  13. Bajpai, P., Bhardwaj, N.K., Bajpai, P.K. and Jauhari, M.B. (1994) J. Biotechnol. 38(1), 1.

  14. Bajpai, P. and Bajpai, P.K. (1996) Tappi J. 79(4), 225.

  15. Bajpai, P. and Bajpai, P.K. (1997) Advances in Biochemical Engineering/ Biotechnology Vol. 56 (edited by T. Scheper, Springer-Verlag, Germany), p. 1.

  16. Bajpai, P. and Bajpai, P.K. (1999) InPaper International, 3(4), 17.

  17. Bajpai, P. and Bajpai, P.K. (1996) Organochlorine Compounds in Pulp and Paper Mill Effluents - Genesis and Control, PIRA International, U.K.

  18. Mishra, D.K., Joshi, H.C., Bhatia, H.S., Chandran, D.P. and Lakhotia, R.L. (2001) IPPTA Convention Issue, p. 5.

  19. Bajpai, P. and Bajpai, P.K. (2001) Appita 54(4), 381.

  20. Bhardwaj, N.K., Bajpai, P. and Bajpai, P.K. (1995) Appita 48(5), 378.

  21. Bhardwaj, N.K., Bajpai, P. and Bajpai, P.K. (1996) J. Biotechnol., 51, 21.

  22. Bajpai, P. and Bajpai, P.K. (1998) Tappi J. 81(12), 111

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