The yeasts of British fresh sausage and minced beef

Three hundred and eighty three yeasts isolated from samples of unsulphited or sulphited sausages and skinless sausages and minced beef were characterized in detail.Debaryomyces hansenii was the most commonly isolated yeast from most samples followed byCandida zeylanoides andPichia membranaefaciens. The presence of sulphite in sausages did not appear to affect the numbers and range of yeasts present but did affect their relative proportions. A survey of one factory showed that meat intended for sausage production and equipment harboured the same range of yeasts that are found in the finished products.     

Psychrophilic yeasts isolated from marine fish

Yeasts were isolated from marine fish using low incubation temperatures. The isolates were screened for their ability to grow at 4 C and 30 C. Isolates growing at 4 C but not at 30 C were considered to be psychrophilic and were selected for further study. Approximately 25% of the isolates were in this category. The isolates comprised the following genera:Candida, Cryptococcus, Debaryomyces, Rhodotorula, Torulopsis andTrichosporon. Rhodotorula infirmo-miniata accounted for 50% of the isolates andTrichosporon pullulans 10%. Other species were present in numbers below the 10% level. The distribution of the species between the two sample areas is discussed. The vitamin requirements and optimum growth temperatures of the isolates were assessed.     

Effects of pesticides on yeasts isolated from agricultural soil

The effect of six various pesticides on the growth of yeasts isolated from agricultural soil was investigated. Two herbicides (with the effective substances lactofen and metazachlor), two fungicides (with the effective substances fluquinconazole and prochloraz), and two insecticides (with the effective substances cypermethrin + chlorpyrifos and triazamate) were tested. It is evident that there are considerable differences in inhibition effects of studied pesticides. The fungicide with the effective substance prochloraz inhibited the growth of majority of yeast strains. The insecticide triazamate at concentration 0.6 mM restricted or inhibited growth of all tested strains. The strains of the genus Cryptococcus were the most sensitive to pesticides, while the strains of the species Cystofilobasidium capitatum, Debaryomyces occidentalis var. occidentalis, and Trichosporon cutaneum were the most resistant.     

Radiation resistance of lactobacilli isolated from radurized meat relative to growth and environment

Of 113 lactobacilli isolated from radurized (5 kGy) minced meat, 7 Lactobacillus sake strains, 1 L. curvatus strain, and 1 L. farciminis strain were used for radiation resistance studies in a semisynthetic substrate (i.e., modified MRS broth). Five reference Lactobacillus spp., one Staphylococcus aureus strain, and one Salmonella typhimurium strain were used for comparative purposes. All L. sake isolates exhibited the phenomenon of being more resistant to gamma-irradiation in the exponential (log) phase than in the stationary phase of their growth cycles by a factor of 28%. Four references strains also exhibited this phenomenon, with L. sake (DSM 20017) showing a 68% increase in resistance in the log phase over the stationary phase. This phenomenon was not common to all bacteria tested and is not common to all strains with high radiation resistance. Four L. sake isolates and three reference strains were used in radiation sensitivity testing in a natural food system (i.e., meat). The bacteria were irradiated in minced meat and packaged under four different conditions (air, vacuum, CO2, and N2). Organisms exhibited the highest death rate (lowest D10 values [doses required to reduce the logarithm of the bacterial population by 1] ) under CO2 packaging conditions, but resistance to irradiation was increased under N2. The D10 values of the isolates were generally greater than those of the reference strains. The D10 values were also higher (approximately two times) in meat than in semisynthetic growth medium.     

Multicenter survey of in vitro antifungal resistance in yeasts of medical importance isolated from Spanish patients

Twelve Spanish laboratories collected 325 yeast clinical isolates during a 30 day's period, among them 224 Candida albicans, 30 Candida glabrata, and 27 Candida parapsilosis. In vitro antifungal susceptibility to amphotericin B, ketoconazole, fluconazole and itraconazole was determined by an agar diffusion test (Neo-Sensitabs, Rosco, Denmark). All the isolates tested were susceptible in vitroto amphotericin B and nearly all (97.2%) to itraconazole. In vitrosusceptibility to fluconazole and ketoconazole was high (90.2% and 91.4% of isolates, respectively) but showed variations depending on the species tested. Resistance to fluconazole and ketoconazole was low in C. albicans (4% and 3%, respectively), but 30% of Candida guilliermondii and 36% of C. glabrata isolates were resistant to fluconazole. Ketoconazole resistance was observed in 40% of C. glabrata, and 17% of Candida tropicalis. Resistance to antifungal drugs is very low in Spain and it is related to non-C. albicans isolates.     

Radiation resistance of lactobacilli isolated from radurized meat relative to growth and environment.

Of 113 lactobacilli isolated from radurized (5 kGy) minced meat, 7 Lactobacillus sake strains, 1 L. curvatus strain, and 1 L. farciminis strain were used for radiation resistance studies in a semisynthetic substrate (i.e., modified MRS broth). Five reference Lactobacillus spp., one Staphylococcus aureus strain, and one Salmonella typhimurium strain were used for comparative purposes. All L. sake isolates exhibited the phenomenon of being more resistant to gamma-irradiation in the exponential (log) phase than in the stationary phase of their growth cycles by a factor of 28%. Four references strains also exhibited this phenomenon, with L. sake (DSM 20017) showing a 68% increase in resistance in the log phase over the stationary phase. This phenomenon was not common to all bacteria tested and is not common to all strains with high radiation resistance. Four L. sake isolates and three reference strains were used in radiation sensitivity testing in a natural food system (i.e., meat). The bacteria were irradiated in minced meat and packaged under four different conditions (air, vacuum, CO2, and N2). Organisms exhibited the highest death rate (lowest D10 values [doses required to reduce the logarithm of the bacterial population by 1] ) under CO2 packaging conditions, but resistance to irradiation was increased under N2. The D10 values of the isolates were generally greater than those of the reference strains. The D10 values were also higher (approximately two times) in meat than in semisynthetic growth medium.     

Influence of thickeners on the fragmentation of fish meat sausage by mastication

The influence of food thickeners (potato starch, guar gum, and xanthan gum and deionized water) on the breakdown of solid food was numerically analyzed, and an investigation was made into the cumulative size distribution of food fragments, textural properties, sensory evaluation and maximum transit velocity of a bolus in the pharynx.The results suggest that evaluating the breakability into small pieces was easily influenced by the addition ratio of the dispersion medium. However, in respect of the destruction process for the solid body, each sample was more strongly affected by the type of the dispersion medium than by the addition ratio of this medium.The destruction process was strongly influenced by the history of the breakdown caused by mastication when a liquid dispersion medium was added to the solid. However, when a high-viscosity sol was added to the solid, the destruction process was random and not affected by any history.     

Phenol degradation by yeasts isolated from industrial effluents

Yeast strains of the genera Aureobasidium, Rhodotorula and Trichosporon were isolated from stainless steel effluents and tested for their ability to utilize phenol as the sole carbon source. Fourteen strains grew in the presence of up to 10 mm phenol. Only the strain Trichosporon sp. LE3 was able to grow in the presence of up to 20 mm phenol. An inhibitory effect was observed at concentrations higher than 11 mm, resulting in reduction of specific growth rates. Phenol degradation was a function of strain, time of incubation and initial phenol concentration. All strains exhibited activity of catechol 1,2-dioxygenase and phenol hydroxylase in free cell extracts from cells grown on phenol, suggesting that catechol was oxidized by the ortho type of ring fission. Addition of glucose and benzoate reduced the phenol consumption rate, and both substrates were used simultaneously. Glucose concentrations higher than 0.25% inhibited the induction of phenol oxidation by non-proliferating cells and inhibited phenol oxidation by pre-induced cells.     

The ability of saprotrophic bacteria isolated from natural habitats to lyse yeasts

More than 600 bacterial strains isolated from different horizons of steppe biogeocenoses and zoogenous loci (diplopod intestines and feces) were tested for the ability to lyse yeast cell walls. About half of the strains that were isolated from biotopes with active degradation of plant debris (steppe litters and diplopod intestines and feces) were found to possess yeast-lytic activity. Most of the yeast-lytic strains belonged to the genera Streptomyces, Promicromonospora, Oerskovia, and Agromyces. The yeast-lytic activity of actinobacteria from the genera Agromyces, Mycobacterium, and Micrococcus has not previously been reported.     

A note on the leavening activity of yeasts isolated from Nigerian palm wine

The role of the yeast flora of Nigerian palm wine in the leavening activity of the beverage was investigated by subjecting organisms from the wine to dough-raising tests. Those with appreciable leavening activity were identified as Saccharomyces cerevisiae and Candida spp. They produced maximum dough volumes in 3–4 h at 37°C. The study has provided experimental evidence that yeasts contribute to the leavening activity of palm wine and has identified strains which have potential utility in commercial bread baking.