Microbiological characterization of Gioddu, an Italian fermented milk

Gioddu, also known as “Miciuratu”, “Mezzoraddu” or “Latte ischidu” (literally meaning acidulous milk), is the solevariety of traditional Italian fermented milk. The aim of the present study was to elucidate the microbiota andthe mycobiota occurring in artisan Gioddu sampled from three Sardinian producers by combining the results ofviable counting on selective culture media and high-throughput sequencing. Physico-chemical parameters werealso measured. The overall low pH values (3.80–4.22) recorded in the analyzed Gioddu samples attested thestrong acidifying activity carried out by lactic acid bacteria during fermentation. Viable counts revealed thepresence of presumptive lactococci, presumptive lactobacilli and non-Saccharomyces yeasts. A complex (kefirlike)microbiota of bacteria and yeasts was unveiled through sequencing. In more detail, Lactobacillus delbrueckiiwas found to dominate in Gioddu together with Streptococcus thermophilus, thus suggesting the establishment of ayogurt-like protocooperation. Unexpectedly, in all the three analyzed batches from two out of the three producersLactobacillus kefiri was also detected, thus representing an absolute novelty, which suggests the presenceof bioactive compounds (e.g. exopolysaccharides) similar to those characterizing milk kefir beverage. Mycobiotapopulation, studied for the very first time in Gioddu, revealed a more complex composition, with Kluyveromycesmarxianus, Galactomyces candidum and Geotrichum galactomyces constituting the core species. Further research isneeded to disclose the eventual occurence in Gioddu of probiotic cultures and bioactive compounds (e.g. exopolysaccharides,angiotensin-converting enzyme inhibitory peptides and antimicrobial compounds) with potentialhealth-benefits for the consumers.