Enhanced survival of GroESL-overproducing Lactobacillus paracasei NFBC 338 under stressful conditions induced by drying

Abstract

GroESL-overproducing Lactobacillus paracasei NFBC 338 was dried, and its viability was compared with that of controls. Spray- and freeze-dried cultures overproducing GroESL exhibited approximately 10-fold and 2-fold better survival, respectively, demonstrating the importance of GroESL in stress tolerance, which can be exploited to enhance the technological performance of sensitive probiotic cultures.

FIG. 1.

(a) Survival of L. paracasei NFBC 338 spray-dried in the presence of RSM (20%, wt/vol) at outlet temperatures of 95 to 100°C. Powders were formulated with cultures containing pGRO2 or pMSP3535. Powders were pour plated in MRS (open bars) and MRS containing NaCl (5%, wt/vol) (shaded bars). (b) Survival of L. paracasei NFBC 338 freeze-dried in the presence of RSM (20%, wt/vol) at outlet temperatures of 95 to 100°C. Powders were formulated with cultures containing pGRO2 or pMSP3535. Powders were pour plated in MRS (open bars) and MRS containing NaCl (5%, wt/vol) (shaded bars). The results are the means of triplicate drying trials, and the standard deviations are indicated by the error bars.

FIG. 2.

(a) Survival of spray-dried L. paracasei NFBC 338 during storage of powder at 4°C (▪ and □), 15°C (▴ and ▵), and 37°C (⧫ and ⋄). The solid symbols indicate powders prepared with cultures containing pGRO2, while the open symbols indicate powders prepared with cultures containing pMSP3535. (b) Survival of freeze-dried L. paracasei NFBC 338 during storage of powder at 20°C (▪ and □) and 37°C (▴ and ▵). The solid symbols indicate powders prepared with cultures containing pGRO2, while the open symbols indicate powders prepared with cultures containing pMSP3535. The results are the means of triplicate drying trials, and the standard deviations are indicated by the error bars.

FIG. 3.

(a and b) TEM images of spray-dried L. paracasei NFBC 338 containing pGRO2. (c) TEM image of spray-dried L. paracasei NFBC 338 containing pMSP3535. (d and e) TEM images of freeze-dried L. paracasei NFBC 338 containing pGRO2 (d) and pMSP3535 (e). Magnification, ×60,000. Bars = 0.5 μm.