Impact of Lactic Acid Bacteria and Bifidobacterium on the Survival of Bacillus subtilus During Fermentation of Wheat Sourdough

Abstract

The aim of this work was to monitor the survival of rope-forming Bacillus subtilus ATCC6633 during three stages of sourdough fermentation with or without Lactobacillus acidophilus 20552 and/or Bifidobacterium lactis Bb 12. Strains of lactic acid bacteria (LAB) and one strain of bifidobacterium were tested for their antimicrobial activities, wherein L. acidophilus ATCC20552 recorded the greatest inhibition zones, followed by Bf. lactis Bb12, while L. acidophilus ATCC4495 and Lactobacillus plantarum ATCC14917 exhibited moderate activities. Sourdoughs were made using L. acidophilus and/or Bf. lactis with added B. subtilus and fermented for 72 h. Microbiological and physicochemical properties of dough samples were periodically (at three stages) determined. Total bacterial, yeasts and molds counts (logo cfu/g) gradually increased during fermentation and reached the maximum at the third stage. Addition of LAB strains, individually or in combination, recorded lower total bacterial counts as well as higher yeasts and molds counts than other treatments. Starter treatments recorded the highest LAB initially and during all fermentation stages. Spore-forming bacteria counts were sharply decreased during fermentation stages in all starter treatments while counts gradually increased in positive control (with only B. subtilis). At the end of fermentation, spore-forming bacteria were not detected in starter treatments. pH values of sourdoughs decreased gradually till the end of fermentation. Starter treatments recorded the lowest pH values during all fermentation stages. Total titratable acidity (TTA) increased after the first fermentation stage and these increments were higher in starter treatments than both positive and negative controls. It could be concluded that using three-stage fermentation method gives L. acidophilus and Bf. lactis the chance to completely inhibit rope-forming B. subtilus. Practical Applications: Cereal-based foods represent an important source of biological as well as of cultural diversity, as testified by the wide range of derived fermented products. A trend that is increasingly attracting bakery industries as well as consumers is the use of biotechnology to produce novel products, characterized by peculiar flavor, better nutritional value and longer shelf life. The aim of our work was to monitor the survival of rope-forming B. subtilus during stages of sourdough fermentation with or without LAB. The results showed that LAB recorded low total bacterial counts, low pH values and high TTA in sourdough. Using three-stage fermentation method may give LAB the chance to inhibit rope-forming B. subtilus.