| The consumption of paper and cardboard is increasing as the rapid development of the world economy led people to improve living standards.In facing of the shortage of forest resources,the use of secondary fiber deinked pulps has became the main means to satisfy the need.In order to adapt to the actual needs of the future deinking papermaking manufacturers and to achieve a better secondary fiber deinking efficiency and deinking results,this study highly expressed two kinds of ?-amylase BlAmy and AmyK and the one with higher enzymatic activity was chosen to mixed in a certain proportion with lipase ARL and xylanase S7 to deinking with three kinds of wastepapers(MOW,PHOT,ONP),the specific experimental results are as follows:Flask fermentation supernatant of recombinant amylase GS115/pHKA-BlAmy is up to5.82U/m L at 144 h.It has an optimum temperature of 40?,optimum pH of 8 and 60%activity can be maintained in the range from 6 to 10.The activity of flask fermentation recombinant amylase GS115/pPIC9K-AmyK is very high,and its supernatant reach 5984U/m L at 120 h and 3L fermenter is 7.7 fold higher than flask fermentation that reach 40200U/mL.It has an optimum temperature of 50?,optimum pH of 6 and it can maintain a relatively high pH stability in the range from 6 to 8.It also can maintain more than 60% residual activity with incubation in 50-70?for 30 min.The deinking result was good when XLA was used to deink mixed office waste paper(MOW).The best dosage of amylase in XLA was 30U/ g dry pulp.Under this condition,the brightness of deinked pulp was the highest and ERIC was the lowest,and the deinking efficiency was 2.94%.The addition of amylase could further improve the efficiency of XL enzyme deinked pulp,XLA(30)deinked pulp has improved tensile,tearing and bursting index;amylase can help reduced the MOW fine fiber content,increased the weight average fiber length,changed the fiber curl index and kink index.The degree of crystallinity of deinked pulp is the highest under the condition of XLA(30),which is the same as that of XLA(30)deinked pulp in the previous study.Chemical method ineffective for non-contactprinting paper like MOW.The deinking result was also good when XLA was used to deink ooks and magazines waste paper(PHOT).The best deinking result of XLA was 50U/g dry pulp,the deinking efficiency of deinked pulp was 13.63%.The addition of amylase could improve the strength of deinked pulp,XLA(50)deinked pulp was better than the XL,and tensile and tear index have improved with breaking index decreased;amylase can also help reduced the PHOT fine fiber content,increased the weight average fiber length,changed the fiber take-up index And the kink index.The degree of crystallinity of the deinked pulp was the highest under the condition of XLA(50),which was consistent with the improvement of XLA(50)deinked pulp strength in the previous study.The chemical method can deink PHOT,but the deinking efficiency was not as good as enzymatic deinking.The addition of small amount of amylase did not improve brightness or reduce ERIC.On the contrary,excessive amylase had a side effect on the optical properties of deinked pulp.Compared with XL deinked pulp,the addition of amylase damaged the strength of deinked pulp,and that of XLA(10)deinked pulp had the highest brightness and the lowest value of ERIC.When the amount of amylase was 10U/g,amylase can help to increase the content of ONP fine fibers,reduce the weight average fiber length,change the fiber's curl index and kink index;the deinked pulp of LW increased;The crystallinity was the lowest for XLA(10),which was consistent with the impaired strength of XLA(10)deinked pulp in the previous study.Chemical method was the best for the flexographic printing paper like ONP. |
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