Fermentation conditions affecting the bacterial growth and exopolysaccharide production by Streptococcus thermophilus ST 111 in milk-based medium
Autor: | Tom Adriany, Frederik Vaningelgem, L. De Vuyst, Medana Zamfir |
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Rok vydání: | 2004 |
Předmět: |
Streptococcus thermophilus
Whey protein Cultured Milk Products Nitrogen Protein Hydrolysates Lactose Bacterial growth Biology Polysaccharide Applied Microbiology and Biotechnology Models Biological Hydrolysate fluids and secretions Starter Food microbiology Animals Food science Biomass chemistry.chemical_classification Polysaccharides Bacterial Temperature food and beverages Caseins General Medicine Hydrogen-Ion Concentration biology.organism_classification Culture Media Milk Biochemistry chemistry Peptones Fermentation Food Microbiology Biotechnology |
Zdroj: | Journal of applied microbiology. 97(6) |
ISSN: | 1364-5072 |
Popis: | F. VANINGELGEM, M. ZAMFIR, T. ADRIANY AND L. DE VUYST. 2004. Aims: To study the effect of different fermentation conditions and to model the effect of temperature and pH on different biokinetic parameters of bacterial growth and exopolysaccharides (EPS) production of Streptococcus thermophilus ST 111 in milk-based medium. Methods and Results: The influence of temperature and pH was studied through fermentation and modelling. Fermentations under non-pH controlled conditions with S. thermophilus ST 111 indicated that the EPS production was low in milk medium, even if additional nitrogen sources were supplemented. Under pH-controlled conditions, addition of whey protein hydrolysate to the milk medium resulted in a fivefold increase of the EPS production. This medium did not contain polysaccharides interfering with EPS isolation. Primary and secondary modelling of different fermentations revealed an optimum temperature and pH of 40� C and constant pH 6AE2, respectively, for growth in milk medium supplemented with whey protein hydrolysate. Maximum EPS production was observed in the range of 32‐42� C and constant pH 5AE5‐6AE6. Whereas growth and maximum EPS production were clearly influenced by temperature and pH, the specific EPS production was only affected by stress conditions (T ¼ 49� C). Conclusions: Addition of whey protein hydrolysate to milk medium resulted in an increased growth and EPS production of S. thermophilus ST 111 under pH-controlled conditions. A modelling approach allowed studying the influence of temperature and pH on the kinetics of both growth and EPS production. Significance and Impact of the Study: The use of an appropriate milk-based medium and a combined model of temperature and pH can be of practical importance for the production of yoghurt or other fermented milks as well as for process optimization of the large-scale production of starter strains to be used for their EPS production. |
Databáze: | OpenAIRE |
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