Characterization of Yeasts Isolated from Parmigiano Reggiano Cheese Natural Whey Starter: From Spoilage Agents to Potential Cell Factories for Whey Valorization

Abstract

Whey is the main byproduct of the dairy industry and contains sugars (lactose) and proteins (especially serum proteins and, at lesser extent, residual caseins), which can be valorized by the fermentative action of yeasts. In the present study, we characterized the spoilage yeast population inhabiting natural whey starter (NWS), the undefined starter culture of thermophilic lactic acid bacteria used in Parmigiano Reggiano (PR) cheesemaking, and evaluated thermotolerance, mating type, and the aptitude to produce ethanol and bioactive peptides from whey lactose and proteins, respectively, in a selected pool of strains. PCR-RFLP assay of ribosomal ITS regions and phylogenetic analysis of 26S rDNA D1/D2 domains showed that PR NWS yeast population consists of the well-documented Kluyveromyces marxianus, as well as of other species (Saccharomyces cerevisiae, Wickerhamiella pararugosa, and Torulaspora delbrueckii), with multiple biotypes scored within each species as demonstrated by (GTG)5-based MSP-PCR. Haploid and diploid K. marxianus strains were identified through MAT genotyping, while thermotolerance assay allowed the selection of strains suitable to grow up to 48 °C. In whey fermentation trials, one thermotolerant strain was suitable to release ethanol with a fermentation efficiency of 86.5%, while another candidate was able to produce the highest amounts of both ethanol and bioactive peptides with potentially anti-hypertensive function. The present work demonstrated that PR NWS is a reservoir of ethanol and bioactive peptides producer yeasts, which can be exploited to valorize whey, in agreement with the principles of circularity and sustainability.

Insights on the bacterial composition of Parmigiano Reggiano Natural Whey Starter by a culture-dependent and 16S rRNA metabarcoding portrait

“…1 F). These results agreed with data previously collected from other PR-NWS samples 25 , 26 . The lack of detectable level of ethanol in all NWS suggest that yeasts either preferably consume lactate or engage a respiratory sugar catabolism.…”

“…Among spoilage microbes, yeasts can utilize lactose and lactate reducing NWS acidifying performance. Among yeasts isolated from PR NWS, only Kluyveromyces marxianus breakdowns lactose, but all the other species, such as Torulaspora delbrueckii , Wickerhamiella pararugosa , and Saccharomyces cerevisiae , are galactose-fermenting yeasts 26 . The inverse relationship between yeast contamination and L. helveticus could depend on the ability of L. helveticus to ferment both glucose and galactose, leaving no sugar moieties available for yeast respiration.…”

“…pH was measured directly using a pH meter (Crison Instruments, Barcelona, Spain), without dilution. Titratable acidity was determined in 50 mL of NWS using the Soxhlet–Henkel method with 0.25 N NaOH and recorded in Soxhlet–Henkel degrees (°SH/50 mL) 26 . Acidification rate of NWS samples was assessed as previously reported 61 and expressed as Δ°SH/50 mL.…”

Microbial Dynamics of a Specialty Italian Raw Ewe’s Milk Cheese Curdled with Extracts from Spontaneous and Cultivated Onopordum tauricum Willd

“…However, Corbo et al [ 69 ] remarked the predominance of Y. lipolytica in ewe’s milk, which is characterized by a higher fat content than cow’s and goat’s milk. As for Wickerhamiella pararugosa (synonym Candida pararugosa ), this yeast has recently been found among the minority species in various dairy products [ 13 , 70 , 71 ] and milk [ 72 ]. Air is considered the main contamination source of Cladosporium spp.…”

Genotypic and Phenotypic Diversity ofKluyveromyces marxianusIsolates Obtained from the Elaboration Process of Two Traditional Mexican Alcoholic Beverages Derived from Agave: Pulque and Henequen (Agave fourcroydes) Mezcal

“…As emphasized by several authors, K. marxianus exhibits a substantial genetic and physiological diversity as illustrated by the variety of habitats from which it can be isolated [1,32,33]. This diversity has mainly been studied in strains isolated from dairy products [15,[34][35][36]. However, it has been recently proposed that K. marxianus strains isolated from agave or associated with agave-based fermentations may represent a divergent clade compared to strains from dairy environments and other habitats [37].…”