title: Effects of salt concentration and pH on structural and functional properties of Lactobacillus acidophilus: FT-IR spectroscopic analysis.
abstract: The effects of sodium chloride concentration and varying pH levels on the structural and functional properties of Lactobacillus acidophilus were investigated. Reconstituted skim milk was inoculated with Lb. acidophilus at varying salt concentrations (0, 1, 2, 5 and 10% NaCl) and pH levels (4.0, 5.0 and 6.0) and ACE-inhibitory activity and proteolytic activity were determined and the viable cell count was enumerated after 24h of fermentation at 37 °C. The degree of proteolysis exhibited an increase with higher salt concentration at pH 5.0 and 6.0. ACE-inhibitory activity was found to be the highest at pH 5.0 at all salt concentrations. Fourier transform infrared spectroscopy results demonstrated significant changes occurring beyond 2% NaCl particularly at low pH (4.0). The findings revealed that significant changes occurred in amide I and amide III regions when Lb. acidophilus was subjected to varying salt concentrations.
authors.affiliation: Food and Nutritional Science, School of Biological Sciences, The University of Hong Kong, Hong Kong.
authors.forename: Akanksha
authors.initials: A
authors.lastname: Gandhi
authors.affiliation: Food and Nutritional Science, School of Biological Sciences, The University of Hong Kong, Hong Kong. Electronic address: npshah@hku.hk.
authors.forename: Nagendra P
authors.initials: NP
authors.lastname: Shah
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D010450:Endopeptidases / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D007779:Lactobacillus acidophilus / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D050296:Microbial Viability / Q000187:drug effects; D008892:Milk / Q000737:chemistry / Q000382:microbiology*; D059748:Proteolysis; D012965:Sodium Chloride / Q000494:pharmacology; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D012965:Sodium Chloride; D010450:Endopeptidases
keywords: ACE-inhibitory activity; FT-IR; Lb. acidophilus; Proteolytic activity; Salt reduction