Endoglucanase Expression In Pichia Pastoris And Its Modification Of Pulp Fibers

In recent times,application of cellulase in the pulp and paper industry has been keptgrowing and received increased attention,such as,improved pulp drainability,reduced beatingenergy consumption,improved paper properties,improved pulp alkali solubility,deinking,pre-bleaching and bleaching ect.Application of enzymes in the pulp and paper can not only improvethe performance of the pulp but also reduce the amount of pollutants and energy consumptionfundamentally.In this study,endoglucanase EG1,cMGL504 and STCE1 are expressed inPichia pastoris respectively,with fermentation preparation and analysis of the product.Experiment with EG1 has studied the following aspects:1)Endoglucanase enzymaticmodification of waste paper and deinking effect.2)Endoglucanase enzymatic modification ofkraft pulp and enzymatic beating effect.3)E ndoglucanase enzymatic modification of kraft pulpduring recycling.The results are followed:1.Using a signal peptide for EG 1 expression in P.pastoris is better than the signal peptidefrom EG1 its own.Flask fermentation supernatant is up to 18.8U/ml and 10L fermenter canreach 180U/ml at 144h.Recombinant endogl ucanase EG1 has an opti mum temperature of 50?,optimum pH of 4 and 80%activity can be maintained in the rangefrom weakly acidic to neutralpH.2.Using their own peptides for CMGL504 and STCE1 expression in P.pastoris is betterthan the a signal peptide.Flask fermentation supernatant of cMGL504 reach 12U/ml at 120h.R ecombi nant endogl ucanase c M G L 504 has an opti mum temperature of 50?,opti mum pH of8 and it can maintain a relatively high pH stability in neutral range.Flask fermentationsupernatant of STCE1 reach 6.6U/ml at 120h.Recombinant endoglucanase STCE1 has anopti mum temperature of 60?,opti mum pH of 4.5 and it can mai ntai n more than 80%resi dualactivity over a wide pH range,25%activity can be retained with incubation in 80? for 1 h.3.Compared with CMGL504 and STCE1,EG1 are chosen as the object of applicationfor its high production.EG1 is poor at ONP deinking but good at MOW deinking.With thecondition of 1U/g,enzyme-treated group increase 2%ISO,reduce ERIC about10%,burstindex and tensile index can be improved by 7.1%and 16.7%,respectively,while the tear index is unaffected.With the condition of 1U/g,incubation at 50? for 1 h,EG1 can reach the same effect of LV K commercial enzyme at 5U/g but with side effect on the mechanical properties of paper sheet.4.With the condition of 3U/g,the paper recycling can be improved.The kink index of the enzyme-treated group decreased sharply by 44.6%after the first recycling.EG1-mediated modification of kraft pulp resulted in paper sheet with the tensile index and burst index increased by 10.1%and 6.6%,respectively.Furthermore,EG1 treatment slowed down the growth of crystallinity and crystal size,which alleviated paper aging.