Properties of Lactococcus Lactis strains isolated from self-fermented dairy products in Belarus
Închide
Articolul precedent
Articolul urmator
471 2
Ultima descărcare din IBN:
2021-12-07 10:18
SM ISO690:2012
SAFONOVA, M., NAIDENKO, I.. Properties of Lactococcus Lactis strains isolated from self-fermented dairy products in Belarus. In: Microbial Biotechnology, 12-13 octombrie 2016, Chișinău. Chișinău, Republica Moldova: Institutul de Microbiologie şi Biotehnologie, 2016, Ediția 3, p. 107.
EXPORT metadate:
Google Scholar
Crossref
CERIF

DataCite
Dublin Core
Microbial Biotechnology
Ediția 3, 2016
Conferința "Microbial Biotechnology"
Chișinău, Moldova, 12-13 octombrie 2016

Properties of Lactococcus Lactis strains isolated from self-fermented dairy products in Belarus


Pag. 107-107

Safonova M., Naidenko I.
 
Institute of Microbiology of the NAS of Belarus
 
Disponibil în IBN: 14 martie 2019



Teza

Unique properties, taste, odor, consistence of fermented milk and cheese products are determined by selection of starter and adjunct microbial cultures and their specific characteristics. Strains of species Lactococcus lactis (L. lactis) represent lactic acid bacteria most frequently and widely used in food industry. Strains L. lactis T8, KM1, 4/4c were solated from spontaneously fermented unpasteurized cow or goat milk and curd samples from private farms in Minsk suburbs and further were tested for valuable properties (growth rate and acidogenesis, halotolerance, proteolytic and antagonistic activity). The resulting cultures displayed traits typical for lactococci and generated acid metabolites during submerged growth in MRS liquid nutrient medium. Spherical or oval cells forming chains of variable length were distinguished by positive Gram-staining and lack of sporulation. Arginine hydrolysis test with ammonium emission proved positive, whereas gas evolution from glucose was not recorded. All examined lactococci readily utilized glucose, lactose, fructose, galactose, maltose. None of them consumed raffinose and rhamnose, sucrose was digested only by strain L. lactis T8, xylose by L. lactis 4/4c, cellobiose by T8 and 4/4c. The optimal temperature for all studied cultures was 280C. The strain L. lactis 4/4c demonstrated the highest level of biomass accumulation after 24 h of fermentation on MRS medium. The strain L. lactis T8 showed the highest sensitivity to temperature of 37 0C and 43 0C, and demonstrated 4.4 and 15.5-times fall in biomass accumulation, respectively. Experiments on growth dynamics of L. lactis T8, KM1 and 4/4c cultured on skim milk demonstrated steady rise in viable cell titer during the initial 9 h of fermentation, reaching 2.9–8.3 bln CFU/ml, then it plateaued until 24 h and gradually decreased to 1.8–3.8·108 CFU/ ml (10.3–46.1 times) by 72 h. The values of cell fission constant at exponential growth phase varied slightly among tested lactococci (1.46–1.57 h-1). Investigation of acid generation in the course of microbial population development on skim milk indicated intense pH drop throughout log growth phase, followed at stationary phase so that by 24 h the level of active acidity (pH) was downgraded to 4.1–4.2. The examined bacteria were prolific acid producers and diminished pH values by 1.34–1.65 within the first 6 h of the culture. Proteolytic activity assays revealed distinctions in lactococcal strains. L. lactis T8 showed the maximal enzymatic activity on skim milk. The contents of free aminoacids (calculated as tyrosine) in analyzed milk samples upon microbial treatment constituted 0.74 μM/ml after 24 h and 1.08 μM/ml after 168 h. Good growth of tested lactococci was established when 4 % NaCl was added into the medium: by 48 h biomass accumulation made up 65–70 % of the control parameter (in NaCl-free medium). Build-up of salt concentration to 6.5 % was marked by significant growth inhibition (down to 20 % of the control) and suppression of acidogenesis in all lactococci. Comparative investigation of physiological-biochemical properties shown by microbial isolates enabled to deduce that the examined lactococcal strains possessed similar growth parameters when cultured on skim milk and enhanced acid generation potential. The obtained data will be considered in selecting constituents of complex microbial starter cultures for food industrial processes.