Abstract
In this study, the fermentation and proteolysis of two co-cultures were investigated. Two fermented cow skim-milk lactoferrin 1 (LF1) and lactoferrin 2 (LF2) were prepared. LF1 was inoculated with Bifidobacterium longum (Bf I) and Streptococcus thermophillus (St I) while LF2 was inoculated with Lactobacillus plantarum (Lb O) and B. longum (Bf I). Incubation was at 42°C for 8 h. The enumeration revealed bacterial growth in all fermented milk. Maximum growth of (Lb O) and (Bf I) was observed when mixed together after 2 h of fermentation in comparison with Bf I and St I with values of 10 9 and 3.10 8 cfu/ml, respectively. The kinetics of acidification (pH and lactic acid production) gave significant values (p < 0.01) for LF2 when compared to LF1 and sterile milk (LS). The proteolytic activity (functions α-NH 2 released in M/mg) and total proteins (in μg/mg) gave significant values (p < 0.05) for LF2 when compared to LF1. Two mixed cultures (Lb O- Bf I) and (St I-Bf I) showed proteolysis of s-lactoglobulin (s-Lg) and -lactalbumin (α-la).
Highlights
Throughout history, humans have made use of lactic acid bacteria (LAB), which are distributed widely in nature
lactoferrin 1 (LF1) was inoculated with Bifidobacterium longum (Bf I) and Streptococcus thermophillus (St I) while lactoferrin 2 (LF2) was inoculated with Lactobacillus plantarum (Lb O) and B. longum (Bf I)
This study showed the potentiality of two strains of LAB S. thermophillus (St I), L. plantarum (Lb O) and one strain of bifidobacteria B. longum (Bf I) to grow in skim cow’s milk and to degrade the major proteins, -lg and α -lactalbumin ( -la)
Summary
Throughout history, humans have made use of lactic acid bacteria (LAB), which are distributed widely in nature. Twelve genera of LAB are recognized (Axelsson, 2004), starter cultures of LAB belong to one of four genera, with the dairy LAB representing the largest group This includes species of Lactococcus, Streptococcus, Leuco-. In addition to lactic acid producers, other types of organisms may be employed to impart therapeutic properties to fermented products, such as Bifidobacterium sp. One important result of the addition of the LAB necessary for fermentation is the resulting proteolytic activity. This activity is slight, resulting in a breakdown of only 1 to 2% of milk protein (Rasic and Kurmann 1978), it is essential for the release of small peptides and amino acids for the growth of the bacteria. The principal substrate for such proteolysis is casein, but limited degradation of whey proteins may occur. (Chandan et al, 1982; El-Zahar et al, 2003; Khalid et al, 1991)
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