Isolation, Biochemical Characterization and DNA Identification of Yogurt Starters &i&Streptococcus thermophilus&/i& & &i&Lactobacillus delbrueckii ssp. bulgaricus&/i& in Gaza Strip

摘要

Background: Milk is a healthy human nutrient, which is fermented to yogurt by lactic acid bacteria, mainly Streptococcus salivarius ssp, thermophilus and Lactobacillus. delbrueckii ssp. bulgaricus . This study aimed to isolate thermophilic starter bacteria from homemade yogurt made in Gaza Strip. The study sought to define both the biochemical and molecular characteristics of the isolated bacteria. Results: Three of the isolates were identified as Streptococcus thermophiles while two isolates were recognized as Lactobacillus delbrueckii ssp. bulgaricus . All five identified isolates showed worthy acidification capacity. Based on these characters, strains were applied for making yogurt either as single pure cultures or as mixed cultures. When using mixed cultures from S. thermophiles and L. bulgaricus , all tested combinations showed positive results. Conclusion: Isolated strains showed remarkable biotechnological characters. The isolates are expected to stimulate and improve quality of the yogurt when they are used as mixed starter cultures.