Effect of the pH of growth on the survival of Lactobacillus delbrueckii subsp. ...

• Author(s): Silva, J. ; Carvalho, A. S. ; Ferreira, R. ; Vitorino, R. ; Amado, F. ; Domingues, P. ; Teixeira, P. ; Gibbs, P. A.
• Date: 2005
• Persistent ID: http://hdl.handle.net/10400.14/2857
• Origin: Veritati - Repositório Institucional da Universidade Católica Portuguesa
• Subject(s): Heat shock proteins; Lactobacillus bulgaricus; pH growth conditions; Spray-drying; Storage; Thermotolerance
• Document Type: Article
• Language: English

Description

Aims: The aim of this study was to optimize survival of Lactobacillus delbrueckii subsp. bulgaricus during spraydrying and subsequent storage through optimizing the pH of growth conditions. Methods and Results: Cell concentrates previously grown without or with pH controlled were spray-dried and stored at 20ºC and heat treated at 57ºC. 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. Significance and Impact of the Study: 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.