Skip to main content
Article thumbnail
Location of Repository

Novel Techniques for the Characterisation of\ud Exopolysaccharides Secreted by Lactic Acid Bacteria

By Marcus J. Chadha


This project investigated the structures and physical characteristics of exopolysaccharides\ud (EPSs) secreted by lactic acid bacteria.\ud \ud \ud The structure of a novel exopolysaccharide (EPS) produced by Lactobacillus acidophilus 5e2 has been characterised. Analysis of the anomeric region of the H-NMR showed that the repeating oligosaccharide contained seven monosaccharides. GC-MS showed the structure to consist of D-glucose, D-galactose and D-N-acetyl-glucosamine in a molar ratio of 3:3:1. The linkage analysis showed that there were two terminal, three di-linked and two tri-linked monosaccharides, and in collaboration with data generated from a series of D-NMR experiments, an overall structure was determined.\ud \ud \ud The weight-average molecular weight (Mw) of the EPS secreted by Lactobacillus acidophilus 5e2 when grown in skimmed milk was monitored during extended fermentation times. During the exponential growth phase, the increase in Mw closely followed the increase in yield of EPS. Under the fermentation conditions applied in this study, few if any new polysaccharide chains were formed during this growth phase despite a twenty five-fold increase in the cell count; almost the entire increase in yield can be accounted for by an increase in chain length.\ud \ud These results suggested that synthesis of new EPS chains is switched off during the exponential and stationary phase of fermentation. The increase in\ud yield observed in this period is a consequence of the bacteria's ability to extend existing chains right up to the mid-stationary phase. These results raise questions about the factors that control EPS production and chain length.\ud Depolymerisation techniques have been shown to reduce the Mw of the polysaccharide in a controlled manner. The H-NMR results have shown that the physical methods, constant pressure and ultrasonic disruption break the EPS randomly through the repeating oligosaccharide unit; polydispersity data suggests that the breakages were occurring midchain.\ud A change to the peaks in the anomeric region of the H-NMR spectrum showed that depolymerisation, by acid hydrolysis, was chemically modifying the EPS structure. The approximate intrinsic viscosities of the EPS produced by Lactobacillus acidophilus 5e2 were determined to range between 0.6–2.0 dL g-1 for the Mw range of 1.59x105 – 4.78x105 g mol-1.\ud \ud \ud A capillary zone electrophoresis method was developed to determine the monosaccharide\ud composition of two EPS samples. The method successfully determined D-glucose and Dgalactose,\ud but a peak for D-N-acetyl-glucosamine was not seen. The method was sensitive compared to current techniques, but not as low as using a HP-AEC-PAD.\ud \ud \ud A novel method using LC-MS was developed for the linkage analysis of EPSs. Methylation, hydrolysis and reductive amination were used to derivatise the polysaccharide, and the fragmentation patterns were examined to determine the different linkage positions. Due to undesirable further fragmentation the method could not unequivocally differentiate between the different linkage positions, but the method was capable of resolving the monosaccharides residues with different linkage positions, at approximately the correct relative ratio

Topics: Q1, QD
OAI identifier:

Suggested articles


  1. (1996). Abstracts of
  2. (1944). Acta Physicochem. URSS
  3. (1949). Advance Carbohydrate Chemistry
  4. (2005). Anaerobe doi
  5. (2008). Analytica Chimica Acta doi
  6. (1996). Analytical Biochemistry doi
  7. (1995). Analytical Chemistry doi
  8. (1960). Antonie Van Leeuwenhoek doi
  9. (1997). Applied and Environmental Microbiology
  10. (2008). Applied Biochemistry and Biotechnology doi
  11. (1997). Applied Microbiology and Biotechnology doi
  12. Basic one- and two-dimensional doi
  13. (1964). Biochem (Tokyo)
  14. (1997). Bioscience Biotechnology and Biochemistry doi
  15. (1995). Biotechnology Advances doi
  16. (2009). British pharmacopoeia; Stationery Office: London,
  17. (1996). Carbohydr Res doi
  18. (1990). Carbohydrate Polymers doi
  19. (1996). Carbohydrate Research doi
  20. (2007). Comprehensive Glycoscience doi
  21. (2007). Comprehensive Glycoscience; Elsevier Science, doi
  22. (2005). Current Opinion in Chemical Biology doi
  23. Eds. Introduction to polymers; doi
  24. (1994). Electrophoresis doi
  25. (2004). Encyclopedia of Food Microbiology doi
  26. (2003). Fems Microbiology Letters doi
  27. (1990). Fems Microbiology Reviews doi
  28. (2007). Food Chemistry doi
  29. (2008). Food Control doi
  30. (2008). Food Hydrocolloids doi
  31. (1995). Food Polysaccharides and their Application 1st ed.;
  32. (1999). Food Science and Technology-Lebensmittel-Wissenschaft & Technologie
  33. (2000). Immunology and Cell Biology doi
  34. (1996). In High Resolution Separation and Analysis of Biological Macromolecules, doi
  35. (1984). London Acedemic Press Inc
  36. (2006). Manufacturing Yogurt and Fermented Milks, 1st ed.; doi
  37. (2005). Mass Spectrometry Reviews doi
  38. (2002). Medical Biochemistry, 4th ed.; doi
  39. (2003). Medical Hypotheses doi
  40. (1986). Microbiological Reviews
  41. (1986). Microbiological Sciences
  42. (2005). Mutation Research-Fundamental and Molecular Mechanisms of Mutagenesis doi
  43. (1998). Nippon Nogeikagaku Kaishi-Journal of the Japan Society for Bioscience Biotechnology and Agrochemistry
  44. (1998). Process Biochemistry doi
  45. (1913). Soc doi
  46. (2003). Trends in Biotechnology doi
  47. (1994). Ultrasonics Sonochemistry doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.