Bioactivity of highly hydrolytic bacteria isolated from Chiapas Cheese
: México

  • Joana Filipa Horta Machado (Student)

Student thesis: Master's Thesis


Lactic acid bacteria (LAB) are widely used in food industry. This group of microorganisms notonly have the ability to produce lactic acid, which contributes to the taste and texture offermented products but also show the capability to produce, during milk fermentation, bioactivepeptides that can be important in human health by having antihypertensive, antimicrobial, antioxidative, antithrombotic and mineral-binding activities. Chiapas cream cheese, a traditionaltype of Mexican cheese, is obtained through a prolonged acid-enzymatic coagulation of cowraw milk and has unique sensory characteristics due to the endogenous LAB in milk from thisregion. Thus, the aim of this project was to select and study the bioactivity of high hydrolyticisolates from Chiapas cheese. An initial selection from 84 isolates was made for production ofdiacetyl and a negative production of catalase. Further analysis to measure the degree ofhydrolysis and to obtain the peptide profile was carried out. Selected isolates were compared toLactobacillus helveticus DSM 13137 and used to study the potential activity of peptidesreleased through lactic fermentation. The antioxidant properties of whey fractions, after 24h and48h of fermentation in reconstituted skimmed milk (RSM), were evaluated by twospectrophotometric methods. Scavenging of the cation radical of 2, 2’-Azino-Bis (3–Ethylbenzthiazoline–6-Sulfonic Acid) (ABTS) ranged from 50%-86% while ferric reducingantioxidant power assay presented variable FRAP values among the selected strains. Anangiotensin-converting enzyme (ACE) inhibitory assay by HPLC was performed showinginhibitions by average mean of 75% in the isolates compared to 96% in DSM 13137. Thepotential inhibitory effects of the bioactive peptides produced by the selected isolates were alsotested against some food-poisoning pathogenic organisms: Escherichia coli, Salmonella Typhi,Salmonella Enteritidis and Listeria monocytogenes, using the paper disc method, showingcases with inhibitory zones by average mean of 12 mm diameter zone. The results indicatedsuggest that these strains could have applications as starters in dairy industry and as a sourceof new bioactive peptides with different modes of action.
Date of Award9 Feb 2017
Original languageEnglish
Awarding Institution
  • Universidade Católica Portuguesa
SupervisorJauregi Paula (Supervisor) & Maria Manuela Pintado (Co-Supervisor)


  • Lactic acid bacteria
  • Chiapas cheese
  • Bioactive peptide
  • Fermentation


  • Mestrado em Microbiologia Aplicada

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