title: Soybean whey protein/chitosan complex behavior and selective recovery of kunitz trypsin inhibitor.
abstract: Proteins in soybean whey were separated by Tricine-SDS-PAGE and identified by MALDI-TOF/TOF-MS. In addition to β-amylase, soybean agglutinin (SBA), and Kunitz trypsin inhibitor (KTI), a 12 kDa band was found to have an amino acid sequence similar to that of Bowman-Birk protease inhibitor (BBI) and showed both trypsin and chymotrypsin inhibitor activities. The complex behavior of soybean whey proteins (SWP) with chitosan (Ch) as a function of pH and protein to polysaccharide ratio (RSWP/Ch) was studied by turbidimetric titration and SDS-PAGE. During pH titration, the ratio of zeta potentials (absolute values) for proteins to chitosan (|ZSWP|/ZCh) at the initial point of phase separation (pHφ1) was equal to the reciprocal of their mass ratio (SWP/Ch), revealing that the electric neutrality conditions were fulfilled. The maximum protein recovery (32%) was obtained at RSWP/Ch = 4:1 and pH 6.3, whereas at RSWP/Ch = 20:1 and pH 5.5, chitosan consumption was the lowest (0.196 g Ch/g recovered proteins). In the protein-chitosan complex, KTI and the 12 kDa protein were higher in content than SBA and β-amylase. However, if soybean whey was precentrifuged to remove aggregated proteins and interacted with chitosan at the conditions of SWP/Ch = 100:1, pH 4.8, and low ionic strength, KTI was found to be selectively complexed. After removal of chitosan at pH 10, a high-purity KTI (90% by SEC-HPLC) could be obtained.
authors.affiliation: State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University , 1800 Lihu Avenue, Wuxi, Jiangsu Province 214122, People's Republic of China.
authors.forename: Xingfei
authors.initials: X
authors.lastname: Li
authors.forename: Die
authors.initials: D
authors.lastname: Dong
authors.forename: Yufei
authors.initials: Y
authors.lastname: Hua
authors.forename: Yeming
authors.initials: Y
authors.lastname: Chen
authors.forename: Xiangzhen
authors.initials: X
authors.lastname: Kong
authors.forename: Caimeng
authors.initials: C
authors.lastname: Zhang
mesh_terms: D048271:Chitosan / Q000737:chemistry*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D008894:Milk Proteins / Q000737:chemistry*; D013025:Glycine max / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014360:Trypsin Inhibitor, Kunitz Soybean / Q000737:chemistry / Q000494:pharmacology*; D000067816:Whey Proteins
chemical_list: D008894:Milk Proteins; D000067816:Whey Proteins; D048271:Chitosan; D014360:Trypsin Inhibitor, Kunitz Soybean