Abstract:

Rice bran was fermented with Bacillus natto and the 64-hour fermentation broth was separated by centrifugation to harvest supernatant. In the presence of protectant, the supernatant was vacuum lyophilized to produce a synbiotics. To maximize the survival rate of Bacillus natto, several protectants with good performance were chosen and formulated and subsequently, their optimal formulation was investigated using orthogonal arrays design. Moreover, the tolerance of synbiotics developed to simulated gastroenteric environment was explored. Results showed that the optimal compound lyophilization protectant formula consisted of skimmed milk powder 15%, sucrose 5% and β-cyclodextrin 5%. This formula resulted in an obvious increase of survival rate of Bacillus natto, reaching up to 82.1%. The synbiotics developed exhibited good tolerance to gastric fluid, intestinal fluid and digestive enzymes and could be stored for a long period of time under cold environment. Its hydroxyl free radical scavenging rate presented a dramatic decrease during storage at 25 or 37 ℃, whereas only a slight decrease was observed at 4 ℃.

Key words: Bacillus natto, rice bran, synbiotics, lyophilization, protectant, antioxidation