Application Of Enzyme-induced Protein Hydrogel And Analysis Of Protein Fouling During Filtration

In order to investigate the application of protein aggregation behavior in drugrelease, transglutaminase was used as the cross-linker to help the casein solution toform hydrogel. Konjac glucomannan (KGM) was used as the auxiliary material in thehydrogel to improve the strength and the stability of casein hydrogel. SEM, FT-IR,DSC, and so on were used to investigate the internal structure of hydrogel. We studiedthe absorbent and the stability of the hydrogel by the viscosity test, swellingexperiment, and in vitro degradation experiment. The hydrogels with KGM were usedas the drug carrier embedding docetaxel and levofloxacin hydrochloride for drugrelease. The in vitro release was used to test the effect of drug release.In order to dissolve the fouling problem in industrial process, bovine serumalbumin (BSA) and lysozyme were used as the model proteins to investigate thefouling during the ultrafiltration process in this paper. The operation conditions, suchas, stirring speed, molecular weight cut off (MWCO) of the membrane, the method ofmembrane regeneration, and the influence of ion exchange resin adding in thefiltration process. The fouling behaviors of BSA and casein hydrolysates duringmicrofiltration were also studied. The ion exchange resin in the process wasconsidered as the important factor to study its effects on the flux during the membraneprocess. The SEC-UV-RI-MALLS was used to analyze the change in molecularweights of protein before and after microfiltration, which can help us to deeplyinvestigate the structures of protein during the filtration. After the filtration process,SEM was used to examine the membrane surface.All the conclusions of the study are showed as followed:(1) In the casein hydrogel cross-linked by MTG, the addition of KGM can reducethe gelation time and improve the viscosity in the gelation process. The stability ofhydrogel with KGM was improved because of the hydrogen bonds between caseinand KGM. The crystallization occurs during the gelation process. The hydrogel has agood swelling ratio.(2) Docetaxel and levofloxacin hydrochloride were embedded by caseinhydrogel with KGM for drug release. The effects of drug release were both good. Thehydrophobic drug had a certain release ratio after long time release, while thehydrophilic drug hardly released at that time. The hydrogel is fit to hydrophobic drugfor long-time release and hydrophilic drug for short-time release. (3) The increase in stirring speed at a certain range can improve the flux duringthe ultrafiltration. The irreversible fouling always occurs when the molecular weightof protein is similar as the MWCO of the membrane. If the reversible fouling occurs,NaOH solution can be used to regenerate the membrane. Though the ion exchangeresin added in the filtration process cannot improve the flux, it can reduce the time forthe membrane to reach the steady-state balance during the filtration.(4) During the microfiltration process, ion exchange resin is not only incapableof improving the flux of BSA solution, but also reduces the flux. On the contrary, theparticle can improve the flux of casein hydrolysates. Compared with the solutionsbefore filtration, the protein concentrations of both BSA and casein hydrolysatessolution decreased. This indicated that the protein could adsorb on the membranesurface during filtration.