Preparation And Application Of The Porous Starch

Porous starch is a new type of modified starch,the surface of particles distribute many porous honeycombs with adsorption properties.However after the starch into the holes,the grain structure becomes unstable,Physical properties such as mechanical strength may redue,and the structure collapses easily,which affects adsorption capacity.The functional group of porous starch only has hydroxyl.In order to improve these properties,using glutaraldehyde cross-linke porous starch to enhance its stability and resistance,grafting polyethyleneimine to solve its single surface functional groups.Preparing a more excellent immobilization carrier can expand the application fields of Porous Starch?This research use corn starch as raw material,preparating porous starch by enzymatic method,the oil absorption rate is used as the evaluation index.The optimal enzymatic hydrolysis conditions were determined by single factor and orthogonal experiments,the opltimum conditions as follows:Alpha-starch enzyme:glucoamylase1:4,enzyme dosage 5%,the reaction system pH 6,the enzymatic hydrolysis temperature 50 ?,the time of enzymatic hydrolysis 21 h.Under the optimum conditions,the oil absorption rate of porous starch was 77.65%.The primary and secondary factors affecting the rate of oil absorption were enzymolysis temperature > the amount of enzyme> pH>enzymolysis time.Using scanning electron microscope to observe the microstructure of porous starch,found that the surface of porous starch distributes many moderate depth of the micropores.To solve the problem of porous starch surface single functional group,grafting polyethylene,trinitrobenzene sulfonic acid is used qualitative analysis,determinning the amino content of modified porous starch by titration,amination density is 0.735 mmol / g.The porous starch was cross-linked with glutaraldehyde,settlement plot as an evaluation index.The cross-linking temperature is 35 ?,the cross-linking time is 8h,and the concentration of glutaraldehyde is 4%.After modification,its stability was improved,the oil absorption rate was increased by 9.15%.The isoelectric point of porous starch and modified porous starch are measured by Zeta potential instrument,respectively,+6.2mV ?+9.8meV,which proves that graft polyethyleneimine can provide more positive charge characteristic to porous starch.Due to bacteria are usually negatively charged,and the isoelectric point of modified porous starch improves,by electrostatic interactions,which more conducive to bacterial immobilization.E.coli is fixed into the pores of the crosslinked modified starch porous,comparing the immobilized E.coli number of porous starch and modified starch by plate count method,PS-PEI >PS.By SEM picture found that this carrier can be applied to the immobilized E.coli,not only retains the adsorption performance of its holes,but also has better structural stability.In summary,crosslinked modified starch can be used as a excellent immobilized cell carrier.