Cultivability ofStreptococcus thermophilusin Grana Padano cheese whey starters

Abstract

The application of a culture-independent approach, that of reverse transcriptase-length heterogeneity-PCR coupled with epifluorescence microscopy, allowed us to observe that Streptococcus thermophilus is metabolically active, but only partially cultivable in Grana Padano cheese whey starters. A short preincubation of the starters in sterile skimmed whey was followed by cultivation in sterile skimmed whey-enriched M17. This procedure restored the cultivability of S. thermophilus and enabled us to detect S. thermophilus at ranges (10(7)-10(8) CFU mL(-1)) which have rarely been reported in these cultures. The use of cheese whey as a cultivation-revitalization substrate can be useful to obtain an unbiased picture of the microbial composition of whey starters for Grana Padano cheese, thus avoiding an underestimation of S. thermophilus in these cultures.

A Selected Core Microbiome Drives the Early Stages of Three Popular Italian Cheese Manufactures

“…All these methods are based on cultivation of strains prior to molecular analysis, so they are subject to the well-known biases of culture-dependent methods. In fact, the presence of a high unculturable fraction of S. thermophilus in NWCs for GP production has been reported [58]. The occurrence of species-specific genes with substantial sequence heterogeneity can be a valid premise to apply high-throughput sequencing strategies to achieve strain specific monitoring without cultivation [38].…”

Parmigiano Reggiano cheese: evolution of cultivable and total lactic microflora and peptidase activities during manufacture and ripening

“…Subsequently, for each of the following samples, curd 6, 12 and 48 h after extraction, salted cheese (1 month) and cheese at different stages of ripening (2,3,4,6,8,10,12,16 and 20 months) were used; the wheels were cut lengthwise along the vertical axis and a central cheese section (1.0 cm thick) was obtained. Internal and external (0.5 cm from the cheese crust) portions were obtained from these cheese sections and grated before the analysis.…”

“…• C for 72 h to facilitate, respectively, the growth of thermophilic and mesophilic lactobacilli; M17-SSW [12] at 42…”

A review of the molecular approaches to investigate the diversity and activity of cheese microbiota

“…This technique provides a quick and easy way to evaluate technological functionality of many different whey starter cultures on the basis of qualitative and quantitative variations of the dominant LAB species, although LH-PCR is subject to certain biases inherent to the PCR process (Lazzi et al 2004). Length heterogeneity reverse transcriptase PCR has also been applied to study the metabolically active microbial populations recoverable from Grana Padano cheese whey starters (Fornasari et al 2006;Rossetti et al 2008;Santarelli et al 2008). The limit of sensitivity (10 5 CFU.mL −1 ) of S. thermophilus in eight whey starters of Grana Padano cheese suggests a need to combine LH-PCR with traditional cultivation methods (Rossetti et al 2008).…”

“…As active bacteria have a higher number of ribosomes than dead cells, this approach gave an estimate of metabolically active LAB populations present in the whey starters (Fornasari et al 2006).…”