The Composition of Camembert Cheese-Ripening Cultures Modulates both Mycelial Growth and Appearance

Abstract

The fungal microbiota of bloomy-rind cheeses, such as Camembert, forms a complex ecosystem that has not been well studied, and its monitoring during the ripening period remains a challenge. One limitation of enumerating yeasts and molds on traditional agar media is that hyphae are multicellular structures, and colonies on a petri dish rarely develop from single cells. In addition, fungi tend to rapidly invade agar surfaces, covering small yeast colonies and resulting in an underestimation of their number. In this study, we developed a real-time quantitative PCR (qPCR) method using TaqMan probes to quantify a mixed fungal community containing the most common dairy yeasts and molds: Penicillium camemberti, Geotrichum candidum, Debaryomyces hansenii, and Kluyveromyces lactis on soft-cheese model curds (SCMC). The qPCR method was optimized and validated on pure cultures and used to evaluate the growth dynamics of a ripening culture containing P. camemberti, G. candidum, and K. lactis on the surface of the SCMC during a 31-day ripening period. The results showed that P. camemberti and G. candidum quickly dominated the ecosystem, while K. lactis remained less abundant. When added to this ecosystem, D. hansenii completely inhibited the growth of K. lactis in addition to reducing the growth of the other fungi. This result was confirmed by the decrease in the mycelium biomass on SCMC. This study compares culture-dependent and qPCR methods to successfully quantify complex fungal microbiota on a model curd simulating Camembert-type cheese.

Dynamics of Penicillium camemberti growth quantified by real-time PCR on Camembert-type cheeses under different conditions of temperature and relative humidity

“…Molecular tools based on PCR amplifications have been developed for the identification of Penicillium species (Pedersen et al, 1997;Dupont et al, 1999;Niessen, 2008;Lessard et al, 2012). Le Dréan et al (2010) quantified the amount of P. camemberti mycelium in cheeses using real-time PCR.…”

“…In cheese manufacturing trials, the P. camemberti mycelium biomass reached a maximum on d 9 in Coulommiers cheeses, and continued to develop in Carré de l'Est cheeses until d 45. Lessard et al (2012) used a real-time PCR method with TaqMan probes to evaluate the growth dynamics of several dairy yeasts and molds, including P. camemberti in softcheese model curds. They showed that P. camemberti and G. candidum quickly dominated the ecosystem, whereas Kluyveromyces lactis remained less abundant.…”

Roles of Alkyl Hydroperoxide Reductase Subunit C (AhpC) in Viable but Nonculturable Vibrio parahaemolyticus

“…Also, a recombinant plasmid for the VP2468 gene was created to be used as a calibration standard, and a strong correlation (R 2 , 0.999) between the concentration of this target gene and threshold cycle (C T ) values was observed using the present RT-qPCR protocol (see Fig. S2 in the supplemental material) (28,29).…”

Melon aroma-producing yeast isolated from coastal marine sediment in Maizuru Bay, Japan

“…candidum directly and positively contributes to cheese ripening and flavor development of many soft and semi-hard cheeses [28,29]. In Camembert cheese production, G. candidum grows on the outside of the cheese and contributes to the formation of a rind [22,30]. ITS region sequence analysis suggested that strain MS1 is similar to G. candidum Tom1.…”

“…The 26S rRNA D1/D2 and ITS sequence analyses indicated that strains MS1 and MS2 were phylogenetically identified as G. candidum. G. candidum is known as a plant pathogenic fungus and is used for rind formation during Camembert cheese production [21,22]. Geotrichum candidum refers to an anamorph and Galactomyces candidus refers to a teleomorph [19,23].…”