Enzymatic activity of lactic acid bacteria (with antimicrobial properties) isolated from a traditional Spanish cheese
ABSTRACT Twenty-four strains of lactic acid bacteria (LAB) isolated from a traditional Spanish cheese (Genestoso cheese) were evaluated for their enzymatic activities (acidifying and proteolytic abilities and carboxypeptidase, aminopeptidase, dipeptidase, caseinolytic and esterase activities), in order to select indigenous strains of technical interest for the manufacture of cheese. These strains were selected on the basis of their antimicrobial activity relative to five reference strains and were identified as Lactococcus lactis subsp. lactis (thirteen strains), Leuconostoc mesenteroides (two strains), Leuconostoc pseudomesenteroides (one strain), Lactobacillus paracasei (two strains), Lactobacillus plantarum (one strain) and Enterococcus faecalis (five strains). Lactococcus strains were those that showed the greatest degree of acidifying and proteolytic activity. The cell-free extracts (CFE) of L. paracasei exhibited the highest level of aminopeptidase activity. The highest level of caseinolytic activity was shown by the CFE of one strain of L. lactis. High values were also obtained with the CFE of Lactobacillus and of several Leuconostoc. The highest level of dipeptidase activity was found amongst the strains of L. lactis. Carboxypeptidase activity was generally very low or undetectable for the majority of strains. The greatest degree of esterolytic activity was detected for Enterococcus.
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ABSTRACT: Growing expectations of consumers of fermented dairy products urge the search for novel solutions that would improve their organoleptic properties and in the case of rennet cheeses-that would also accelerate their ripening process. The aim of this study was to determine the peptidolytic activities and growth of heat-treated commercial culture of lactic acid bacteria. The analyzed culture was characterized by a relatively high peptidolytic activity. The growth of bacterial culture subjected to heat treatment at 50-80 °C for 15 s, 10 and 3 min was delayed by a few or 10-20 h compared to the control culture. Based on the results achieved, it may be concluded that in the production of rennet cheeses, the application of additional, fermentation-impaired starter cultures (via heating for ten or so minutes) may serve to accelerate their ripening and to improve their sensory attributes.Applied Biochemistry and Biotechnology 12/2014; DOI:10.1007/s12010-014-1453-6 · 1.69 Impact Factor
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ABSTRACT: Background Physico-chemical characteristics, proteolysis and lipolysis were studied throughout the ripening of eight batches of a traditional Spanish variety made from raw cow's milk, in order to establish basis for its industrial production.ResultsThe main compositional characteristics of this cheese after 60 days of ripening were its high proportion of Total Solids (752 g Kg−1 of cheese), an average content of protein (452.8 g Kg−1 TS) and fat (475.1 g Kg−1 TS), and presence of residual lactose (12.5 g Kg−1 TS). Its pH value (4.04) was extremely low. Phosphorus (5.13 g Kg−1 TS) and sodium (8.29 g Kg−1 TS) were the most abundant mineral elements in cheese, whereas calcium levels (1.92 g Kg−1 TS) were very low. Proteolysis extension and depth were very low, which resulted in almost zero degradation of αs1- and β-casein. Fat acidity increased during ripening, reaching final values of 50.1 mg KOH Kg−1 of fat. The main free fatty acid was C16:0, followed by C18:1 and C14:0.Conclusion These results suggest that this variety undergoes a limited proteolysis and moderate lipolysis during ripening. The low pH, the low calcium content and the limited proteolysis led to a crumbly texture in this cheese variety.Journal of the Science of Food and Agriculture 11/2014; 95(4). DOI:10.1002/jsfa.7011 · 1.88 Impact Factor
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ABSTRACT: Background Lactococcus lactis is a lactic acid bacterium that has been used for centuries in the production of a variety of cheeses, as these bacteria rapidly acidify milk and greatly contribute to the flavour of the fermentation end-products. After a short growth phase during cheese ripening L. lactis enters an extended non-growing state whilst still strongly contributing to amino acid-derived flavour formation. Here, a research approach is presented that allows investigation of strain- and amino acid-specific flavour formation during the non-growing state.ResultsNon-growing cells of five selected L. lactis strains were demonstrated to degrade amino acids into flavour compounds that are relevant in food fermentations and differs greatly from production of flavour compounds using growing cells. As observed earlier in other research set-ups and with other microorganisms, addition of NADH, ¿-ketoglutarate and pyridoxal-5-phosphate was demonstrated to be essential for optimal flavour formation, suggesting that intracellular pools of these substrates are too low for the significant production of the flavour compounds. Production of flavours during the non-growing phase strongly depends on the individual amino acids that were supplied, on the presence of other amino acids (mixtures versus single compounds), and on the strain used. Moreover, we observed that the plasmid-free model strains L. lactis MG1363 and IL1403 produce relatively low amounts of flavour components under the various conditions tested.Conclusions By using this simplified and rapid approach to study flavour formation by non-growing lactic acid bacteria, lengthy ripening periods are no longer required to assess the capacity of strains to produce flavours in the long, non-growing state of dairy fermentation. In addition, this method also provides insight into the conversion of single amino acids versus the conversion of a mixture of amino acids as produced during protein degradation. The generated results are complementary to earlier generated datasets using growing cells, allowing assessment of the full flavour forming potential of strains used as starter cultures in industrial food fermentation processes.Microbial Cell Factories 12/2014; 13(1):176. DOI:10.1186/s12934-014-0176-2 · 4.25 Impact Factor