纳豆菌冷冻保护剂的研究

CRYOPROTECTANTS OF NATTO BACTERIA

纳豆菌具有溶解血栓、调节血糖等多种营养保健功能.纳豆菌冻干菌粉的生产过程中,冷冻对菌体的存活率影响较大.在纳豆菌菌悬液冷冻过程中添加5种保护剂:乳糖、甘露醇、麦芽糊精、L-抗坏血酸钠、β-环糊精,分别采用单因素试验和正交试验,测定冷冻前后菌体存活率,筛选出最适的纳豆菌冷冻保护剂.试验结果表明:纳豆菌最适保护剂配方为乳糖浓度为1.2%,甘露醇浓度为3%,麦芽糊精浓度为4.5%,L-抗坏血酸钠浓度为2.5%;纳豆菌菌悬液与该复合保护剂混合,在-20℃下冷冻48 h,存活率达到84.25%.此配方对纳豆菌冻干菌粉的生产具有指导意义.

Natto bacteria has the nutritional function of thrombolytic and regulate blood sugar. But the freezing has a great impact on bacterial survival during the Natto freeze-dried powder production process. The present study was to investigate the optimized formula of the cryoprotectants through the single factor and orthogonal experiment. Five protectants, such as lactose, mannitol, maltodextrin, L-ascorbate sodium and fl-cyclodextrin, were selected in this study. The results showed that optimal formulation of natto bacteria cryoprotectants were： the lactose concentration of 1.2%, the mannose concentration of 3%, the maltodextrin concentration of 4.5% and L-ascorbate sodium concentration of 2.5%. Under these conditions, when the mixture of natto bacteria and cryoprotectants was froze under -20 ~C for 48 hours, the Natto bacteria survival rate was reached to 84.25%. Furthermore, the order of the effect of the five cryoprotectants on the Natto bacteria survival rate was： lactose〉 mannitol〉maltodextrin〉sodium〉L-ascorbate. This might be due to the cell membrane phospholipid dehydration and the polarity between the phospholipid molecules and the Van der Waals＇ force between the cell membrane sugar chains were enhanced, which induced the cell membrane structure phase changed. And the lactose could inhibit the cell membrane phase change through ＂water replacement effect＂. It was concluded that this formula was significance to natto freeze-dried powder production.