Treatment of wood chips using enzymes

Abstract

A method of treating wood chips or saw dust with an enzyme formulation, prior to refining, in order to reduce the total extractives content of the wood chips or sawdust and to modify the wood structure is described herein. The wood chips or sawdust are treated with one or more enzymes such as lipases, esterases, pectinases, cellulases, laccases, hemicellulases and combinations thereof. The enzyme formulation can be applied to the surface of the wood chips or sawdust, e.g. by spraying, or can be impregnated into the wood chips. The enzyme formulation can further comprise one or more surface active agents which can enhance the effectiveness of the enzyme treatment by improving the diffusion or impregnation of the enzymes into the wood chips. The enzyme-based treatment can be applied at any of several different locations prior to the pulping process including chip piles, chip conveyors, chip silos, chips washers, chip washer water stream, impregnation liquor, or during chip storage. The enzyme-based treatment is quick and easy to apply in most commercial mill operations. The enzyme-based treatment is effective at temperatures from about 20° C. to about 100° C., preferably from about 35° C. to about 70° C. The wood chips or saw dust can be treated for a period of time from about 0.10 to about 200 hours, more preferably from about 10 to about 72 hours. The addition of the enzyme formulation into the wood chip or sawdust pile increases the concentration of pitch-degrading enzymes on the chip or dust surfaces which can significantly accelerate the degradation of pitch components inside the chips or sawdust. Decreasing the total extractives content of the wood chips and modifying the structure of the wood chips or sawdust leads to a decrease in the apparent pitch content during pulping and in reduced energy requirements, increased paper strength, improved paper machine runability, and lower costs associated with paper manufacturing.

1 . A method of treating wood chips or sawdust, prior to refining, the method comprising treating the wood chips or sawdust with a formulation comprising one or more enzymes at a concentration of at least about 0.001% by weight of the oven-dried wood chips or sawdust.  
   
   
       2 . The method of  claim 1  wherein the one or more enzymes is selected from the group consisting of lipases, esterases, pectinases, cellulases, hemicellulases, laccases and combinations thereof.  
   
   
       3 . The method of  claim 1  wherein the concentration of the one or more enzymes is from about 0.001% to about 5% by weight of the oven-dried wood chips.  
   
   
       4 . The method of  claim 3  wherein the concentration of the one or more enzymes is from about 0.01% to about 1% by weight of the oven-dried wood chips.  
   
   
       5 . The composition of  claim 1  further comprising one or more surface active agents.  
   
   
       6 . The method of  claim 1  wherein the one or more surface active agents is selected from the group consisting of primary and branched alkoxylates, fatty acid alkoxylates, phosphate esters and their alkoxylates, alkylphenol alkoxylates, block copolymers of ethylene and propylene oxide, alkanesulfonates, olefinsulfonates, fatty amine alkoxylates, glyceride alkoxylates, glycerol ester alkoxylates, sorbitan ester alkoxylates, polyethylene glycol esters, polyalkylene glycols, and combinations thereof.  
   
   
       7 . The method of  claim 6  wherein the concentration of the one or more surface active agents is from about 2% to about 50% by weight of the formulation.  
   
   
       8 . The method of  claim 7  wherein the concentration of the one or more surface active agents is from about 5% to about 20% by weight of the formulation.  
   
   
       9 . The method of  claim 1  wherein the wood chips or sawdust are treated with the one or more enzymes at a temperature from about 20 to about 100° C.  
   
   
       10 . The method of  claim 9  wherein the wood chips or sawdust are treated with the one or more enzymes at a temperature from about 35 to about 70° C.  
   
   
       11 . The method of  claim 1  wherein the wood chips or sawdust are treated with the one or more enzymes for a time ranging from about 0.10 to about 200 hours.  
   
   
       12 . The method of  claim 11  wherein the wood chips or sawdust are treated with the one or more enzymes for a time ranging from about 10 to about 72 hours.  
   
   
       13 . The method of  claim 1  wherein the wood chips or sawdust are treated in a location selected from the group consisting of chip piles, chip conveyors, chip silos, chip washers, chip washer water stream, impregnation liquor, and chip storage.  
   
   
       14 . The method of  claim 1  wherein the wood chips or sawdust are treated by spraying the one or more enzymes onto the wood chips.  
   
   
       15 . The method of  claim 1  wherein the wood chips or sawdust are treated by impregnating the wood chips with the one or more enzymes.  
   
   
       16 . The method of  claim 1  wherein the wood chips or sawdust are washed with water after treatment with the one or more enzymes.  
   
   
       17 . The method of  claim 1  wherein the wash water is removed after the wood chips or sawdust have been treated and washed.  
   
   
       18 . The method of  claim 1  wherein the woodchips or sawdust are treated with the one or more enzymes at a pH of between about 3 and about 9.  
   
   
       19 . The method of  claim 1  further comprising measuring the decrease in the total extractives content in the wood chips or sawdust by comparing the pitch content of a wood pulp sample prepared from wood chips or sawdust treated with a formulation comprising one or more enzymes with the pitch content of a wood pulp sample prepared from untreated wood chips or sawdust.