Studies On Viable But Non-cucturable State Of Lactobacillus Delbrueckii Subsp.Bulgaricus ND02

LAB starter culture could not avoid the damage from production and application,not only leaded to a decrease in survival and activity of cells,but also increased the cost of production.Some published reported that bacteria will enter a so-called VBNC(viable but non-culturable)state under adverse environment,VBNC cells may lose their ability in growing in routine culture medium,once the LAB enter the VBNC state,the VBNC cells not only affected the development of its beneficial effects,but also made a significant influence on evaluating the activity of cells,but they could regain their cultivability by means of suitable condition.In this study,Lactobacillus delbrueckii subsp.bulgaricus ND02(Lb.bulgaricus ND02)was as a object,the induction into and resuscitation from the VBNC state were investigated,and the fermentation characteristics of resusction cells were also analyzed.Various conditions were used to induce and resuscitate the VBNC state of Lb.bulgaricus ND02,the changes in cellular morphology and membrane fatty acid composition were analyzed preliminarily,and the fermentation characteristics between the resuscitated and normal cells were also analyzed.The results showed that Lb.bulgaricus ND02 could enter into the VBNC state in different conditions,among which MRS broth and 4 ? was optimum,which spend 190 days on decreasing the culturable cells from 9.37 × 107 CFU/mL to zero.The average length of VBNC cells were also decreased from 5.91 ±0.64 ?m to 3.74±0.56 ?m,and the surface of the cells became drape,the content of unsaturated fatty acid in the VBNC cells were increased from 37.97±0.42%to 53.68±0.15%.When resuscitated the VBNC cells,rising temperature had no effect on the cells in VBNC state,but modified culture medium was the effective method,among which the skimmed milk adding yeast could recovery the viability cells in 7.83 × 108 CFU/mL.Considering the fermentation characteristics of the resuscitated cells,which also retain a low fermentation activity.Although there was significant differences from the normal cells,the resuscitated cells could produce some flavors compounds during the process of fermentation.In summary,studied VBNC state on the LAB starter culture was important to improve the activity of starter culture or reduce production cost,and also provided a theoretical basis for our LAB starter culture industry application and development.