Exopolysaccharide production by Streptococcus thermophilus SY: production and preliminary characterization of the polymer.

Dipartimento di Biologia, Difesa e Biotecnologie Agro-forestali, Università della Basilicata, Potenza, Italy.
Journal of Applied Microbiology (Impact Factor: 2.2). 02/2002; 92(2):297-306. DOI: 10.1046/j.1365-2672.2002.01487.x
Source: PubMed

ABSTRACT To evaluate the effect of yeast extract (YE) concentration, temperature and pH on growth and exopolysaccharide (EPS) production in a whey-based medium by Streptococcus thermophilus SY and to characterize the partially purified EPS.
Factorial experiments and empirical model building were used to optimize fermentation conditions and the chemical composition, average molecular weight (MW) and rheological properties of aqueous dispersions of the EPS were determined. Exopolysaccharide production was growth associated and was higher (152 mg l(-1)) at pH 6.4 and 36 degrees C with 4 g l(-1) YE. High performance size exclusion chromatography of the partially purified EPS showed two peaks, with a weight average MW of 2 x 10(6) and 5 x 10(4), respectively. The EPS was a heteropolysaccharide, with a glucose : galactose : rhamnose ratio of 2 : 4.5 : 1. Its water dispersions had a pseudoplastic behaviour and showed a higher viscosity of xanthan solutions.
The fermentation conditions and some properties of an EPS produced by Strep. thermophilus, a dairy starter organism, were described.

  • [Show abstract] [Hide abstract]
    ABSTRACT: We have conducted a thorough study of the exopolysaccharide (EPS) produced by strain HK30 of Halomonas stenophila, which we have named haloglycan. This strain was chosen during an ongoing research program aimed at finding novel exopolysaccharide-producing halophilic bacteria in unexplored hypersaline habitats. Strain HK30 was isolated from a saline-wetland in Brikcha (Morocco) and identified as belonging to the species Halomonas stenophila. It produced EPS mainly during the exponential growth phase and to a lesser extent during the stationary phase. Culture parameters influenced both bacterial growth and EPS production, EPS yield always being directly related to the quantity of biomass. Under optimum culture conditions strain HK30 produced 3.89 gram of EPS per litre of medium. The polymer was a sulphated heteropolysaccharide composed of two fractions, with molecular masses of 8.2×10(4) and 1.4×10(6). The crude EPS contained 44±0.1% w/w carbohydrates and the following monosaccharide composition: glucose (24±1.73), glucuronic acid (7.5±0.37), mannose (5.5±0.17), fucose (4.5±0.36), galactose (1.2±0.17) and rhamnose (1±0.05) (%, w/w). It produced solutions of high viscosity and pseudoplastic behaviour that showed interesting flocculating and emulsifying activities and was also involved in forming biofilm.
    International journal of biological macromolecules. 08/2014;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This work investigates the influence of incubation temperature and culture media on exopolysaccharides (EPS) production. The S. thermophilus BN1 an EPS-producer strain isolated from cow milk was examined in this study. Skimmed milk, whole milk and cheese whey, were selected as culture media and two different temperatures were also tested. The EPS produced in the different studied conditions was purified and quantified. The strain BN1 was able to produce EPS in all established conditions. However, significant differences were observed in the amounts of produced EPS. The production of EPS reached the maximum values at 37°C in skimmed milk with amount of 548 PDM mg l -1 , followed by the amounts of 375 PDM mg l -1 and 325 PDM mg l -1 respectively in whey and whole milk. In addition, a slight significant difference was noted on the biomass, pH and lactic acid values obtained from the three fermented substrates (p <0.05). The present results demonstrate that incubation temperature (37°C) had a significant (P<0.05) effect on the EPS production by S. termophilus BN1.
    International Conference on Biology, Environment and Chemistry; 12/2011
  • [Show abstract] [Hide abstract]
    ABSTRACT: Summary A review is presented on the present status of commercial dairy starter cultures, their practical applications in the dairy industry and potential role as protective cultures. Starter cultures are those microorganisms that are used in the production of cultured dairy products such as yogurt, kefir and cheese. The natural microflora of milk is inefficient, uncontrollable, and unpredictable, or is destroyed by the heat treatments applied to the milk. A starter culture can provide particular characteristics in a more controlled and predictable fermenta- tion. The characteristic and properties of mesophilic and termophilic lactic acid bacteria (LAB), yeast and mould starter cultures were discussed. The primary function of lactic starters is the production of lactic acid from lactose. There are 3 groups of LAB starter cultures: single strain, single species and multispecies, in which the number and properties of LAB are known. Fermentation of milk by LAB is one of the oldest forms of practiced biopreservation. Due to proteolytic and lipolytic activities and production of exopolysaccharides (EPS) LAB also has an influence on flavor, aroma, color, smell, acidity and viscosity of final products. There are also kefir starter cultures used in the dairy industry instead of traditional kefir grains that contain lactococci, homofermentative and heterofermentative lactobacilli, yeasts and acetic acid bacteria. The positive aspect of yeasts and moulds used in dairy technology is also reviewed. It is known that many yeasts and mould strains are used for cheese making as co-starters with LAB, due to their proteolytic and lipolytic properties.

Full-text (2 Sources)

Available from
Oct 8, 2014

Similar Publications