Diversity of fungal flora in raw milk from the Italian Alps in relation to pasture altitude

Abstract

The present paper explores the diversity of mycobiota inhabiting raw milk sampled at different altitudes (1400 m, 1800 m, 2200 m) from cows grazing Alpine pastures of Valle d’Aosta (North-Western Italian Alps). To this aim, multilocus sequencing was performed at barcodes commonly used for fungal identification (ITS1, D1/D2 domains of the 26S rRNA gene, and part of the β-tubulin gene). A total of 31 species were detected, most of them yeasts, followed by moulds and by 2 sequences of macroscopic fungi. Several yeasts and moulds were well-characterized inhabitants of the dairy environment, known to positively contribute to cheesemaking. Among these, Candida was the most represented genus with a tendency to cluster at the highest altitudes (6 over 8 observations at ≥ 1800 m), and Kluyveromyces marxianus the most abundant single species, retrieved at all altitudes. The environmental ascomycetous Atrotorquata lineata, never put in relation with food nor described outside North-America, was another species among those most frequently retrieved and was detected in 6 milks at 1400 and 1800 m. The remaining fungi, in general never reported in milk, were mostly environmental. Many of them resulted associated with plants as pathogens or symbionts. Finally, the highest sampled altitude yielded a significant fungal diversity (17 species). This work enlarges the knowledge of fungal consortia inhabiting raw milk and introduces microbial ecology among the altitude-dependent factors, in the composition of Alpine pastures, with the potential of shaping the properties of milks and cheeses, together with the already described physical, chemical and botanical variables.

Yeast and mould dynamics in Caciofiore della Sibilla cheese coagulated with an aqueous extract of Carlina acanthifolia All.

“…This is especially true for yeasts and moulds, whose occurrence and diversity in vegetable coagulants have been very poorly explored (Roseiro et al ., ). The importance of these microorganisms in cheese manufacturing is being increasingly acknowledged, due to the many beneficial activities of these microorganisms, including the excretion of growth factors (especially vitamins), the metabolization of lactate/lactose, which enhances the growth of a secondary microbiota constituted by acid‐sensitive bacteria, the production of alkaline metabolites and aromatic compounds, the inhibition of spoilage microorganisms, the enhancement of cheese flavour and aroma through proteolysis and lipolysis, and even probiosis (Beresford et al ., ; Jacques and Casaregola, ; Panelli et al ., ; Padilla et al ., ; Cardoso et al ., ). On the other hand, fungi can also act as spoilage microorganisms, causing cheese defects such as cheese softening, superficial discoloration, early blowing and the development of off‐flavours (Fleet, ; Jakobsen and Narvhus, ; Carreira et al ., ; Wyder et al ., ).…”

Internal transcribed spacer (ITS) sequencing reveals considerable fungal diversity in dairy products

“…Most authors suggest, however, that fungi found in raw milk are typically heat sensitive and that raw milk is thus not an important (direct) source of fungi found in dairy products (Jacques and Casaregola, 2008). A few studies have surveyed the diversity of fungi in raw milk and reported that yeasts are more frequently isolated from raw milk than molds (Callon et al, 2007;Delavenne et al, 2011;Panelli et al, 2013). For example, Panelli et al (2013) tested 40 bulk milk samples across the Italian Alps and most frequently isolated Kluyveromyces marxianus, Atrotorquata lineata, and Candida spp.…”

“…A few studies have surveyed the diversity of fungi in raw milk and reported that yeasts are more frequently isolated from raw milk than molds (Callon et al, 2007;Delavenne et al, 2011;Panelli et al, 2013). For example, Panelli et al (2013) tested 40 bulk milk samples across the Italian Alps and most frequently isolated Kluyveromyces marxianus, Atrotorquata lineata, and Candida spp. Importantly, these studies identified some fungal species that had not previously been found in raw milk, suggesting that the fungal diversity associated with raw milk remains to be fully understood.…”

Atrotorquata lineata as a proxy for Juncus roemerianus, Part I: Atrotorquata lineata as a proxy for Juncus roemerianus in surface sediments from high-level salt marshes in the southeastern United States

“…They are longitudinally striate and have 5 to 7 germ slits at each apex. Kohlmeyer and Volkmann-Kohlmeyer further suggest that A. lineata is probably host-specific to J. roemerianus, though there has been one recent report of A. lineata being detected in a DNA study of milk from cows grazing in the Italian Alps (Panelli et al 2013).…”