ABSTRACT
Fourteen strains of Candida famata and 7 strains of C. sphaerica originating from blue-veined Rokpol cheese were studied for their ability to produce killer toxins against 3 strains of Yarrowia lipolytica selected as potential starter cultures for cheesemaking. All tested strains revealed killer activity in the presence of salt, at 14 degrees C and pH 4.6. Only one Y. lipolytica strain was resistant to C. famata and C. sphaerica killer toxins.
Subject(s)
Candida/growth & development , Candida/pathogenicity , Cheese/microbiology , Mycotoxins/metabolism , Yarrowia/growth & development , Candida/classification , Culture Media/chemistry , Hydrogen-Ion Concentration , Killer Factors, Yeast , Mycotoxins/pharmacology , Sodium Chloride , Species Specificity , Temperature , Yarrowia/classification , Yarrowia/drug effectsABSTRACT
Yeast microflora on the surface and interior of Rokpol cheese was examined for cheeses produced at three dairies located in Lower Silesia, Poland. Yeast populations on the surface of the cheeses ranged from 10(5)-10(9) cfu/g, but were 10-100 times lower for interior samples. The occurrence and proportions of yeast species varied, depending on the dairy plant and cheese sample. The most frequently isolated species were: Candida famata and C. spherica, followed by C. intermedia and Geotrichum sp. Other species such as Saccharomyces kluyveri, C. kefyr and C. lipolytica were found occasionally. Extracellular and intracellular proteolytic and lipolytic activities were examined for 39 isolates of C. famata.
Subject(s)
Candida/isolation & purification , Cheese/microbiology , Candida/enzymology , Colony Count, Microbial , Food Microbiology , Hydrogen-Ion ConcentrationABSTRACT
Four commercial strains and two mutants of the yeast species Yarrowia lipolytica were screened using batch fermentation. Strain Y. lipolytica A-101-1.14 (induced with UV irradiation) was found to be the most suitable for citric acid production from glucose hydrol (39.9% glucose and 2.1% other sugars), a byproduct of glucose production from potato starch. The specific rate of total citric and isocitric acid production was 0.138 g/g.h, the yield on consumed glucose 0.93 g/g, and the productivity achieved was as high as 1.25 g/L.h. All of the tested yeast strains were able to utilize only the glucose from the glucose hydrol medium. Thus, some residual higher oligosaccharides remained in the process effluent.
Subject(s)
Citrates/biosynthesis , Fermentation , Glucose/metabolism , Yeasts/metabolism , Citric Acid , Kinetics , Mutagenesis , Ultraviolet RaysABSTRACT
The dynamics of the utilization of hydrocarbons from a synthetic mixture used as sole carbon and energy source in medium during the growth of two strains of yeast, Candida scottii A-31 and Candida rugosa A-7, was studied. The yeasts grew in a mineral medium with 2% of hydrocarbons, on a shaker, for 72 hours. During this time almost complete utilization of n-paraffins in the medium was observed and the biomass increments were 11.2 and 12.64 g of dry wt./l, respectively. The examined strains did not utilize iso-paraffins but were found to metabolize n-paraffins at various rates.
