Survey on community and dynamics of lactic acid bacteria in Grana Padano cheese

tGrana Padano (GP) is a Protected Designation of Origin cheese made with raw milk and natural wheyculture (NWC) that is characterised by a long ripening period. In this study, six GP productions wereconsidered in order to evaluate the trend of microbial dynamics and compare lactic acid bacteria (LAB)population levels in cheeses during the entire cheese-making process. To reach this goal, for each GPproduction, samples of vat raw milk, NWC and cheeses at 48 h, 2, 6, 9 and 13 months were subjected toplate counts and direct counts by fluorescence microscopy, as well as amplicon length heterogeneity-PCR (LH-PCR). Statistical analysis was applied to the results and ecological indices were estimated. It wasdemonstrated that the LAB able to grow in the cheese-environment conditions could arise from bothraw milk and NWC. Starter lactobacilli (SLAB) from NWC were the main species present during acidifica-tion, and non-starter LAB (NSLAB), mainly from milk but also from NWC, were able to grow after briningand they dominated during ripening. The peak areas of LH-PCR profiles were used to determine eco-logical indices during manufacture and ripening. Among cheese ecosystems with different ageing times,diversity, Evenness and Richness were different, with highest bacterial growth and diversity occurring incheese ripening at 2 months. At this time point, which seemed to be a crucial moment for GP microbialevolution, cell lysis of both SLAB and NSLAB was also observed.Sampling modality and statistical analysis gave greater significance to the results used to describe themicrobiological characteristics of a cheese recognised worldwide.