title: Influence of gas-liquid two-phase flow on angiotensin-I converting enzyme inhibitory peptides separation by ultra-filtration.
abstract: BACKGROUND
  Membrane fouling is a major problem in ultra-filtration systems and two-phase flow is a promising technique for permeate flux enhancement. The objective of this research was to study the use of an ultra-filtration (UF) system to enrich angiotensin-I converting enzyme (ACE) inhibitory peptides from tilapia protein hydrolysate. To select the most appropriate membrane and operating condition, the effects of membrane molecular weight cut-off (MWCO), transmembrane pressure (TMP) and cross-flow velocity (CFV) on permeate flux and ACE inhibitory peptide separation were studied. Additionally, the gas-liquid two-phase flow technique was applied to investigate its effect on the process capability.
  
  
  RESULTS
  The results showed that the highest ACE inhibitory activity was obtained from permeate of the 1 kDa membrane. In terms of TMP and CFV, the permeate flux tended to increase with TMP and CFV. The use of gas-liquid two-phase flow as indicated by shear stress number could reduce membrane fouling and increase the permeate flux up to 42%, depending on shear stress number. Moreover, the use of a shear stress number of 0.039 led to an augmentation in ACE inhibitory activity of permeates.
  
  
  CONCLUSIONS
  Operating conditions using a shear stress number of 0.039 were recommended for enrichment of ACE inhibitory peptides. © 2016 Society of Chemical Industry.
authors.affiliation: Department of Natural Product Technology, Faculty of Agricultural Technology, Burapha University Sakaeo Campus, Sakaeo, 27160, Thailand.
authors.forename: Narin
authors.initials: N
authors.lastname: Charoenphun
authors.affiliation: Department of Food Technology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, 90112, Thailand.|Membrane Science and Technology Research Center, Prince of Songkla University, Hat Yai, 90112, Thailand.
authors.forename: Wirote
authors.initials: W
authors.lastname: Youravong
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000302:isolation & purification*; D000818:Animals; D029941:Fish Proteins / Q000302:isolation & purification*; D010455:Peptides / Q000302:isolation & purification*; D011492:Protein Hydrolysates / Q000737:chemistry*; D012212:Rheology; D017210:Tilapia; D014462:Ultrafiltration / Q000379:methods*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D029941:Fish Proteins; D010455:Peptides; D011492:Protein Hydrolysates
keywords: ACE inhibitory peptides; gas-liquid two-phase flow; tilapia protein; ultra-filtration