Population dynamics of lactic acid bacteria during spontaneous malolactic fermentation in industrial cider

A deeper knowledge on the complex microbial ecology of malolactic fermentation (MLF) in spontaneous cider production is essential to understand the cider making process, thus, applicable to develop adequate malolactic starters. Trends in food fermentation focussed on the isolation of proper wild-type strains from traditional products to be used as starter cultures, with the aim of conducting industrial production processes without losing their unique flavour and product characteristics. A mixed inoculum consisted of samples taken from the four main areas of the most traditional cider making region in Spain was used to carry out MLF under controlled laboratory conditions. A culture-based approach was used to investigate the diversity of lactic acid bacteria (LAB) by molecular tools. By monitoring MLF, population dynamics involved in the fermentation process were assessed. Interactions of different microorganisms adapted to a common environment, competition and resistance during the process, give rise to dominant species showing selective advantages. The main aim of this work was the identification of dominant species during the process in order to obtain potential starter cultures with a clear industrial utility. The fermentative capacity of a representative strain belonging to each isolated species, after analysis of interspecific polymorphisms in 16S rRNA sequencing of 84 isolates, was compared. Molecular characterization for the presence of gene coding for exopolysaccharide production (dps gene amplification), acrolein production (pdu gene amplification) and biogenic amine production (tyrdc, hdc and odc genes amplification) was carried out to verify the suitability of the selected strains.