The effect of immobilization on some probiotic properties ofStreptococcus thermophilus strains

Abstract

In this study, the viability of free and immobilized forms of Streptococcus thermophilus A21 and W22 was evaluated in terms of their tolerance of low pH, bile salts and resistance to nisin and penicillin G. The immobilized strains were more resistant to low pH and to bile salts than free strains. Besides, immobilized strains found resistant to nisin and penicillin-G. When compared the amount of L(+) lactic acid and EPS produced by both free and immobilized strains, the decrease of L(+) lactic acid and EPS production in the immobilized strains were found to be insignificant. However, during a two week's storage period at refrigerator and room temperature, there were no significant differences in the viability of immobilized A21 and W22 strains. The results of this research show immobilization of the cells did not impair, or even improved, the probiotic and technological properties of tested strains.

Bile Salts Deconjugation Using Microencapsulated Lactic Acid Bacteria Isolated from Handmade Yogurt

“…For the encapsulation of viable bacterial cells, materials used as excipients should be gentle and non-toxic [19]. The most commonly used for microencapsulation of bacterial cells is alginate due to the fact that alginate is a cheap material and non-toxic for the body [8]. Other materials such as carrageenan, gelatin, chitosan, whey proteins, cellulose acetate phthalate, locust bean gum and starches can be used instead of alginate for encapsulation process [20].…”

“…A great interest has aroused for LAB because of their probiotic properties. The Lactobacillus and Streptococcus strains are among frequently used bacterial strains in probiotic cultures [8]. Among them a combination of S. thermophilus and L. delbrueckii subsp.…”

“…Microencapsulation process is important providing BSH enzymes maximum viability to access to the intestinal tract. Microencapsulation enables high level protection of bacteria from stomach acidity [8,10]. Capsules, as they proceed through the gastrointestinal tract, begin to be deformed, but bacteria, due to encapsulation, are almost never affected in terms of viability [8,20].…”

“…The alginate mixed-suspensions were dropped into a sterile 0.4 mol/l CaCl 2 solution by a peristaltic pump. The mixture was kept at +4°C for 2 h for the separation of encapsulated sodium-alginate beads (300µm in diameter) and settled at the bottom of the bottle as calcium chloride layer [8].…”

“…Microencapsulation is a concept in which biologically active materials are encapsulated in specialized ultra-thin semipermeable polymer membranes [8]. And also, this method is a powerful technology which has been developed for use in the food industry and allows the protection of bacteria [9].…”