Freeze-drying of Enterococcus durans: effect on their probiotics and biopreservative properties

Abstract

The present work studied the preservation of probiotic strains of Enterococcus durans by freeze-drying. The prebiotic lactulose showed to be the best protectant agent for E. durans after freeze-drying and storage at 4 and 25 °C for 92 days. Freeze-dried E. durans LM01C01 was resistant to acid treatment and able to grow in the presence of bile. Also, freeze-dried samples grew in the presence of preservative food ingredients: potassium sorbate and sodium chloride. After addition of dried cultures in a cream cheese, the number of viable bacteria was maintained for 3 months (shelf-life of the products). The spent culture supernatant of E. durans LM01C01 showed inhibitory effects on the pathogens E. coli and S. aureus. Although the addition of dried probiotic to cream cheese did not have any effect on contamination of food matrix with E. coli, a drastic decrease of viability of S. aureus was observed. These results demonstrated the suitability of E. durans strains to develop a dried symbiotic product (probiotic plus prebiotic) that could be added to food matrices or nutraceutical products, that could also tolerate gastrointestinal conditions and may act as biopreservative too.