Production of a novel non-toxicγ-PGA/casein composite hydrogel using MTG and optimization by response surface methodology

Theγ-PGA-based food hydrogel exhibits good biodegradability and biocompatibility,and is non-toxic to humans.In this study,a novel hydrogel(γ-PGA/casein composite hydrogel)was prepared by combining casein with y-PGA separated from natto using microbial transglutaminase(MTG)as the crosslinker.The effects of the MTG mass concentration,gelation time,crosslinking temperature,pH,and the mass ratio of y-PGA to casein on the crosslinking ratio of y-PGA and swelling ratio of theγ-PGA/casein hydrogel were investigated.Furthermore,the synthesis conditions were optimized by response surface methodology to optimize three important factors,i.e.crosslinking temperature,pH and the mass ratio of y-PGA to casein.The results of single factor experiments showed that the MTG mass concentration and crosslinking time had little impacts on the crosslinking ratio of y-PGA and the swelling ratio;the preferred MTG mass concentration,crosslinking time,temperature and pH were selected as 0.3%,7 h,40℃and 7.5;and the preferred mass ratio ofγ-PGA to casein was 0.1 for the crosslinking ratio ofγ-PGA and 0.2 for the swelling ratio.The response surface experiment results showed that the optimum crosslinking temperature,pH and the mass ratio of y-PGA to casein ratio were 42.4℃,7.33,and 0.18,respectively.Under these optimum conditions,the predicted crosslinking ratio of y-PGA and swelling ratio reached 90.35%and 112.07%,which were highly consistent with the experimental values(88.00%and 115.87%).Theγ-PGA/casein composite hydrogel developed in this study shows promising application potential in food industry,biomedical field,and cosmetic industry.