Diversity of Yeast and Mold Species from a Variety of Cheese Types

Abstract

To generate a comprehensive profile of viable fungi (yeasts and molds) on cheese as it is purchased by consumers, 44 types of cheese were obtained from a local grocery store from 1 to 4 times each (depending on availability) and sampled. Pure cultures were obtained and identified by DNA sequence of the ITS region, as well as growth characteristics and colony morphology. The yeast Debaryomyces hansenii was the most abundant fungus, present in 79 % of all cheeses and 63 % of all samples. Penicillium roqueforti was the most common mold, isolated from a variety of cheeses in addition to the blue cheeses. Eighteen other fungal species were isolated, ten from only one sample each. Most fungi isolated have been documented from dairy products; a few raise potential food safety concerns (i.e. Aspergillus flavus, isolated from a single sample and capable of producing aflatoxins; and Candida parapsilosis, an emerging human pathogen isolated from three cheeses). With the exception of D. hansenii (present in most cheese) and P. roqueforti (a necessary component of blue cheese), no strong correlation was observed between cheese type, manufacturer, or sampling time with the yeast or mold species composition.

Fungi in the healthy human gastrointestinal tract

“…commune, foodborne species incapable of growing at 37 C. 39,40 Finally, there is the long tail of rarely-detected fungi which make up most of the species richness in gut mycobiota studies but whose presence in human fecal samples is strictly incidental and cannot be assumed to influence the gut ecology. These include edible mushrooms, 23 plant pathogens (widely reported; see, e.g.…”

Production, Characterization, and Antimicrobial Activity of Mycocin Produced byDebaryomyces hanseniiDSMZ70238

“…Debaryomyces hansenii is one of the most common yeast species in nature and food such as dairy products, including soft, brine, and hard cheese [1–3]. D. hansenii is a halotolerant species and it can be grown in medium supplemented with up to 25% sodium chloride [4].…”

Killer toxin from several food-derived Debaryomyces hansenii strains effective against pathogenic Candida yeasts

“…1 g samples from the outer surface of Romano and blue cheese as well as from shredded Gruyere cheese were placed on the plates and they were incubated for 3 days at either 25 °C or 37 °C. From sample where killer activity had been observed, three samples (10 g each) from the outer surface of that cheese were homogenized in 50ml of sterile 1% peptone using a stomacher Blender 400 and the samples were serially diluted and plated on yeast extract glucose chloramphenicol agar (YEGC) to prevent bacterial growth and incubated for 5 days at 25 °C (Banjara et al, 2015). Colonies were selected based on morphology and color and then restreaked on YEGC agar plates.…”

“…As described in Banjara et al (2015), 44 cheeses (differing in variety and/or manufacturer) were collected from local retailers and sampled for yeasts and molds. DNA was extracted from pure cultures following the method described by Harju et al (2004), and polymerase chain reaction (PCR) was performed using the fungal-specific forward primer ITS1F (Gardes and Bruns, 1993) and the universal eukaryotic reverse primer TW13 (White et al, 1990).…”

“…Debaryomyces hansenii is among the most common yeast species isolated in viable form from foods such as cheeses (Banjara et al, 2015;Breuer and Harms, 2006), due to its ability to grow in the presence of high salt (Breuer and Harms, 2006;Prista et al, 2005), low pH, and low water activity (Capece and Romano, 2009), and its ability to metabolize lactic and citric acids (Ferreira and Viljoen, 2003). In recognition of its food processing potential, D. hansenii has QPS status in the European Union, permitting its use in the production of cheeses and fermented sausages, and is considered a useful organism in food fermentations (Bourdichon et al, 2012).…”