Effect of the pH of growth on the survival of Lactobacillus delbrueckii subsp. bulgaricus to stress conditions during spray-drying.
OBJECTIVE
The aim of this study was to optimize survival of Lactobacillus delbrueckii subsp. bulgaricus during spray-drying and subsequent storage through optimizing the pH of growth conditions.


RESULTS
Cell concentrates previously grown without or with pH controlled were spray-dried and stored at 20 degrees C and heat treated at 57 degrees C. Cells grown under noncontrolled pH were more resistant to both drying and heating than cells grown under controlled pH but no significant differences were observed during storage. The intracellular proteins profile of cells grown under both conditions was studied by two-dimensional SDS-polyacrylamide gel electrophoresis. Eight proteins were identified using automated mass spectrometry (MS) and tandem mass spectrometry (MS/MS) data acquisition. Of the identified proteins, only cochaperonin GroES corresponded to a known heat shock protein (HSP). The other proteins identified are proteins involved in glycolysis. For cells grown under noncontrolled pH the expression of the Hsp70, GroES and GroEL, measured by Western blotting, was enhanced.


CONCLUSIONS
The higher resistance of cells grown under noncontrolled pH correlates with the enhanced production of heat shock proteins.


CONCLUSIONS
Growth of L. bulgaricus under controlled pH (commonly used by the starter cultures production industry) results in cells more sensitive to stresses frequently encountered by the cells during starter cultures preparation/storage/utilization.
Silva
J
J
Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, Porto, Portugal.
Carvalho
A S
AS
Ferreira
R
R
Vitorino
R
R
Amado
F
F
Domingues
P
P
Teixeira
P
P
Gibbs
P A
PA
D001426:Bacterial Proteins / Q000032:analysis; D015153:Blotting, Western / Q000379:methods; D018835:Chaperonin 10 / Q000032:analysis; D018834:Chaperonin 60 / Q000032:analysis; D003890:Desiccation; D015180:Electrophoresis, Gel, Two-Dimensional; D005516:Food Microbiology; D005519:Food Preservation; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D048668:Lactobacillus delbrueckii / Q000502:physiology*; D021241:Spectrometry, Mass, Electrospray Ionization
D001426:Bacterial Proteins; D018835:Chaperonin 10; D018834:Chaperonin 60; D018840:HSP70 Heat-Shock Proteins