Resumen de Direct Application of Rep‐PCR on Type I Sourdough Matrix to Monitor the Dominance and Persistence of a Lactobacillus plantarumStarter Throughout Back‐Slopping
Paola Dolci Kalliopi Rantsiou, Luca Simone Cocolin
This study describes the optimization and application of repetitive element‐PCR (rep‐PCR) technique directly on microbial DNA extracted from type I sourdoughs for fast monitoring of a Lb. plantarumstarter strain (P1FMC) throughout daily back‐slopping. The challenge was to follow and study the performance of a starter culture directly in sourdoughs without cultivation on selective media. The extraction of good quality microbial DNA suitable for amplification from a complex matrix such as dough was the first target. In addition, the objective to obtain a clear rep‐PCR profile referable to a specific starter strain among a microbial community was pursued. Co‐inoculum trials, in flour matrix, with Lb. plantarumP1FMC and L. lactisLC71 strains and, subsequently, type I sourdough back‐slopping trials were performed. The rep‐PCR amplification profiles obtained were clearly referable to that of Lb. plantarumP1FMC starter in both co‐inoculum trials (also when it was present with one order of magnitude less with respect to L. lactisLC71) and back‐slopping trials where it dominated the fermentation process with loads of 108cfu g−1and prevailed on the autochthonous microbiota. Thus, the approach proposed in this paper could be considered a methodological advancement, based on a culture‐independent one‐step rep‐PCR, suitable for fast monitoring of starter performance. In response to practical needs of a bakery factory, a fast method was optimized to monitor the dominance of a starter culture in sourdough back‐slopping in order to intervene quickly in the process in case of poor performance of the starter. Actually, this method may be applied when a single starter strain is used as inoculum. Although this is not the most frequent case in sourdough fermentations, this technological approach could be taken into account for other applications in food fermentations where one‐strain starter cultures are used, or for monitoring microbial biomass production in a bioreactor.
