The evolution of lactic acid bacteria community during the development of mature sourdough

Abstract

In order to follow the composition and changes in lactic acid bacteria (LAB) population of rye flour sourdough that was continuously propagated by a repeated inoculation, sixty-two strains of LAB were isolated and characterized. The LAB were the only bacteria detected, both at the end of the second propagation step and in the stage of mature sourdough (after two weeks of continuous daily refreshment). The stable ecological system in rye sourdough could be established from the second propagation step onward. The predominant genera of LAB during the development of sourdough were lactobacilli, which were grouped in eight clusters. Heterofermentative lactobacilli were in majority in both propagation step two and a mature sourdough participating 56% and 70% of total bacterial count, respectively. The identification based on a phenotypic characterization that was carried out by using a set of 36 tests, showed that the lactobacilli contained in the two sourdough steps did not clearly belong to any known species of the genus Lactobacillus. In addition, the structure of the bacterial population were monitored by two statistical techniques (Hierachical Cluster Analysis and Principal Component Analysis), being applied to phenotypical characteristics of the isolates.U cilju pracenja sastava i promena populacije bakterija mlecne kiseline (BMK) u kiselom testu pripremljenog sukcesivnim svakodnevnim premesavanjem testa od razanog brasna, 62 sojeva BMK je izolovano i okarakterisano. BMK su jedini mikroorganizmi izolovani na kraju drugog premesavanja, kao i u fazi zrelog kiselog testa (nakon 2 sedmice svakodnevnog sukcesivnog premesavanja). Stabilni ekoloski sistem u kiselom testu pripremljenom od razanog brasna uspostavlja se nakon drugog premesavanja. Rod BMK koji dominira u toku razvoja kiselog testa su laktobacili i koji su grupisani u 7 grupa. Heterofermentativni laktobacili dominiraju od drugog premesavanja, kao i u fazi zrelog kiselog testa, pri cemu ucestvuju sa 56%, odnosno 70% u ukupnom broju BMK. Identifikacija na osnovu fenotipskih i fizioloskih svojstava (primenom 36 testa) pokazala je da se laktobacili izzolovani iz kiselih testa ne mogu jasno svrstati u do sada poznate vrste roda Lactobacillus. Pored toga, pracena je struktura bakterijske populacije u kiselom testu primenom dve statistice tehnike (hijerarhijska klaster analiza i analiza glavnih komponenti) na fenotipska svojstva izolata.