The Stability Of Transglutaminase Biosynthesis By Streptoverticillium And Its Effects On Emulsifying Property Of CPI

Transglutaminase(TGase) is a kind of thiol enzyme that catalyzes acryl-transfer reaction, which introduces inter- or intra-molecular covalent crosslinks in many proteins, changing the quality of food products. TGase has been widely used in food industry. The author studied the effects of metal ions on TGase production by Streptoviticillium SK4.001 and the emulsifying property of chickpea protein isolates(CPI) modified by Alcalase and TGase.By studying the effects of initial metal ions in the fermentation medium on TGase production by Streptoviticillium SK4.001, it was found that Zn2+ played an important role in TGase production by Streptoviticillium SK4.001. TGase activity reached highest, when Zn2+ initial concentration in the fermentation medium reached 8.15ug/mL. However TGase activity did not change significantly by increasing Zn2+ initial concentration.TGase activity did not change significantly when the fermentation culture was dialysed with EDTA addition. according to the change of biomass at different Zn2+ initial concentrations, the author considered that Zn2+ was not the component or active centre of TGase. The mechanism of Zn2+ improving TGase production needs to keep on investigating.When the hydrolyzed CPI (DH2.65%) was incubated by 4 U/g pro TGase at pH7.0, 35oC for 50min, its emulsifying capacity reached 0.987, increased 17.64% than that of untreated CPI, however its emulsifying stability was lower than CPI's as 0.819.The CPI's solubility and surface hydrophobicity increased after the CPI being hydrolyzed by Alcalase. However its flexibility did not improve. After the hydrolyzed CPI being incubated by TGase, its solubility and surface hydrophobicity reduced for the crosslink action of TGase. However its flexibility improve significantly. The distributing of surface hydrophobicity area might also be changed too. All of these effects improved the emulsifying property of modified CPI.SDS-PAGE of CPI,CPI hydrolyzate,hydrolyzed CPI crosslink product showed the proteins of molecular mass above 40.1KD reduced significantly for the effect of Alcalase, the effect of TGase polymerized the CPI hydrolysis product, the macropolymer molecules were so large that they were unable to penetrate the stacking or the separation gels in SDS-PAGE. The flexibility and hydrophobicity of CPI was changed with the moleculer mass, and the emulsifying property of CPI was changed too.