INFLUENCE OF PROTECTANTS ON Lactobacillus plantarum SUBJECTED TO FREEZE-DRYING

Abstract

       Lactobacillus plantarum is commonly found in many fermented food products and is an ideal candidate for the development of probiotics, which have healthy benefits for the body. The starter cultures have to be prepared to maintain their activity and stability to make use of the advantages of this species. Freeze-drying is a widely used technique for the preservation and storage of heat sensitive biological materials. However, bacterial cells can suffer from dehydration stress as water is removed. Therefore, to reduce adverse effects, protective substances can be added to samples before being freeze-dried to minimize stress associated with freeze-drying and to increase survival rate. Solutions of trehalose, lactose, trehalose + lactose, skim milk, and 2X lyophilization reagent were used as protective media for Lactobacillus plantarum A17 during freeze-drying. The survival rate, moisture content, and fermentation efficiency after freeze-drying were examined. The results showed that trehalose provided the highest survival rate followed by the combination of trehalose:lactose (64% and 61%, respectively). The moisture contents at the end of the freeze-drying cycle were less than 5% for all protectants tested. The efficiency of fermentation was significantly different (P < 0.01) between freeze-dried cells with and without protectants.