Microbiological characterization using combined culture dependent and independent approaches of Casizolu pasta filata cheese

Aims: Casizolu is a traditional Sardinian (Italy) pasta filata cheese made with
cow raw milk belonging to Sardo-Modicana and/or Bruno-Sarda breeds added
with natural whey starter. This work aims to describe the traditional
technology of this product and to evaluate the microbial groups/species
involved in the first month of ripening.
Methods and Results: Raw milk, curd after stretching and Casizolu cheese
samples from two different farmsteads were subjected to enumeration of
microbial groups, isolation and genotypic characterization of isolates and PCR
temporal temperature gel electrophoresis (TTGE) analysis. The counts of
lactobacilli and lactococci groups in raw milk were about 5–6 log UFC ml
1 of
milk. These counts tended to increase in curd and cheeses, reaching values
higher than 8 log UFC g
1 of cheese. Culture dependent and independent
approaches employed in this work highlighted the fundamental role of
Lactococcus lactis subsp. lactis, Streptococcus thermophilus and Lactobacillus
paracasei in the manufacture and ripening of Casizolu cheese. Other species
frequently isolated were Enterococcus durans, Enterococcus faecium, Enterococcus
italicus while Enterococcus lactis, Streptococcus parauberis, Lactobacillus
plantarum, Lactobacillus pentosus, Lactobacillus brevis, Lactobacillus fermentum
and Lactococcus raffinolactis were isolated occasionally.
Conclusions: Lactococcus lactis subsp. lactis, Strep. thermophilus and
Lact. paracasei were the principal bacterial species involved in the Casizolu
cheese manufacturing and ripening. For the first time, Ent. italicus and
Ent. lactis were isolated in the pasta filata cheese.
Significance and Impact of the Study: This study shows the first data on
microbial groups and species involved in the manufacture of Casizolu cheese
and highlights the role of Lact. paracasei and Enterococcus spp. from the earliest
stages of ripening cheese; furthermore, provides evidence that raw milk cheese
is a source of new strains and therefore a reservoir of microbial biodiversity.