Enzyme Applications in the Pulp and Paper Industries

1
Enzyme Applications in the Pulp and Paper
Industries

• Thomas W. Jeffries
• USDA, Forest Service
• Forest Products Laboratory

2
Pulp and paper processing is one of the largest
uses of biomass today

• Per capita consumption of paper in the United
  States exceeds 300 kg annually.
• Paper consumption increases with standard of
  living.
• Established processes are inefficient and
  environmentally costly.
• Greater emphasis is being placed on fiber recycle.

3
Biotechnology will affect pulp and paper
processing in increasing ways.

• Enhanced bleaching of chemical pulps
• Better removal of ink from recycled fibers
• Disposal of cellulosic fines
• Improved processing of mechanical pulps
• Bioremediation of waste streams

4
Enhanced bleaching by xylanases and mannanases is
becoming commercial.

• Discovering effective enzymes
• Thermostable
• Alkaline active
• High turnover number
• Cloning and producing them in high yield
• Understanding process conditions for application

5
Xylanase treatment economically reduces chlorine
demand in bleaching

• Chlorine bleaching costs about 15 to 18 per
  ton.
• Enzyme treatment reduces chlorine by 30 to 50.
• Xylanase treatment of hardwood pulp costs about
  6 to 10 per ton.
• Other bleaching technologies are more expensive.

6
Enzymatic deinking could become commercial.

• Deinking is critical in fiber recycle.
• Residual ink decreases brightness.
• Toner particles create a conspicuous background.
• Toners and inks are hard to separate from fibers.
• Microbial cellulases facilitate contaminant
  removal.

7
Enzymes might have roles in other pulp and paper
processes.

• Retting
• Bark removal
• Pitch removal
• Lignin removal
• Enhanced fiber bonding
• Inter-fiber bond strength restoration

8
Microbial xylanases for enhanced bleaching of
chemical pulps

• First demonstrated by Liisa Viikari in 1985
• Showed that xylanases rather than lignanases
  could reduce chlorine demand
• Some xylanases are more effective than others
• Commercial products show high thermal stability
  and alkaline activity
• Mechanism is still not completely understood

9
Xylanases enhance bleaching chemical
accessibility and remove chromophores

• Xylan is solubilized during the pulping process
• As the pH drops, xylan is deposited on fiber
  surfaces
• Precipitated xylan blocks extraction of lignin
• Xylan facilitates inter-fiber bonding
• Chromophores in pulp are cross linked to xylan
• Xylanases can release chromophores from fibers

10
Conclusions

• Xylanases reduce chemical bleaching
• Thermo-stable, alkaline-active enzymes are
  commercially available
• Enzymes increase pulp accessibility and
  chromophore release
• Xylanases act synergistically

11
Microbial cellulases can enhance deinking and
toner removal

• Deinking and contaminant removal are major
  barriers in paper recycling
• Toners are particularly difficult to remove
• Resilient plastic polymers
• fused to the fibers
• Cellulases release toners from fiber surfaces
• Cellulases increase drainage rates

12
Enzyme action is affected by paper constituents
and deinking conditions

• Mechanical vs. chemical fibers
• Presence or absence of sizing agents
• Consistency of deinking
• pH of pulp

13
Enzyme action is affected by paper constituents
and deinking conditions

• Chemically-pulped fibers are more susceptible
  than mechanically-pulped
• Sizing agents reduce enzyme activity
• Enzyme action is complemented by maceration
• Many recycled fibers have an alkaline pH due to
  carbonate loading

14
Fungal cellulases work well with acid sized or
mechanical papers

• Low doses of enzymes release toners
• Higher treatments effective for dispersible inks
• Excess enzyme and mechanical action reduces the
  deinking effect
• Xylanases have little effect

15
Sizings reduce the effect of enzymes

• ASA and AKD
• Alkenyl succinic anhydride
• Alkyl ketone dimer
• Added to paper to prevent ink from running
• Increase hydrophobic character of fiber
• Interfere with enzyme action
• Can be overcome by the addition of surfactants

16
Laser and xerographic toners are among the most
difficult to remove

• Nylon based polymers
• Particles do not readily disperse
• Fused to the fiber surface
• Have similar density as fibers
• Dispersible inks used in newsprint and magazines

17
Pilot plant deinking trials have been promising

• Novozyme 342 (Humicola insolens)
• Neutral-active fungal cellulase complex
• Three runs of 2,300 kg each
• 100 toner office waste paper
• Control heat inactivated enzyme
• Enzyme run 1 Ambient pH, 0.4 L/1000 kg
• Enzyme run 2 Adjusted pH to 7.9

18
Enzyme treatment conditions

• Fiberize for 5 min at 16 consistency with 0.125
  surfactant
• Add enzyme batchwise in 10-15 of pulp volume
• Pulp at 14 consistency with enzymes
• 50C, 30 min

19
Conclusions

• Cellulases can remove toners from fibers
• Pulp pH must be in enzyme activity range
• Surfactants overcome presence of sizings
• Mechanical action is a critical variable

20
Enzymatic bleaching

• Marguerite Sykes
• Tony Grabski
• Rajesh Patel

• Vina Yang
• Graziano Elegir
• Zenghui Zhuang

21
Enzymatic deinking

• Marguerite Sykes
• Kathie Cropsey
• John Klungness
• Vina Yang