Carbohydrates for health

Our expertise in the structural analysis of complex carbohydrates enables us to research the role of carbohydrates and beneficial bacteria in human gut health.

Carbohydrate analysis

Complex carbohydrates

Polysaccharides and oligosaccharides (called complex carbohydrates) are made up of linear and branched chains of various sugar building blocks. The chains are often decorated with substituents, such as sulfate, phosphate, pyruvate and acetate.

The properties of these molecules—found in a wide range of food, food ingredients and industrial products—are determined by their structure and substitution patterns. Confirming the structure of these molecules is therefore an essential first step to understanding how they behave, whether gelling or thickening foods, being digested by bacteria in the colon, or in other uses.

Our advanced chemical analytical techniques enable us to find out what these building blocks and substituents are, and how the complex carbohydrate is linked together.

Current research projects

We are currently researching in these areas:

  • understanding how gut bacteria utilise polysaccharides and oligosaccharides in the diet (particularly for infant nutrition)
  • identifying combinations that result in butyrate production in the gut, which is a known health benefit
  • developing new analysis techniques.

Some of these projects are suitable for postgraduate research projects, including Masters and PhD theses. Please contact Dr Alison Daines for more information.

Collaborators

We contribute our analytical expertise to a wide range of collaborative projects.

Our key collaborators include:

Staff

Dr Ian Sims (programme lead) | Dr Tracey Bell | Dr Susie Carnachan | Dr Simon Hinkley

Functional infant formula

We are researching carbohydrate components that may function like those in human milk when incorporated into infant formula. Our research has focused on the sialic acid content, which varies from 5–15 g/L in human milk, but is only present at 50 mg/L in cows’ milk. Sialic acid is an essential component of the glycolipids required for the development of cognitive function.

In a Smart Ideas Phase 1 research programme with the University of Otago, we identified natural ingredients that contain high levels of sialic acid. Phase 2 research is now underway to assess if two of the ingredients can be manufactured at a commercial scale. This work also involves Callaghan Innovation.

Prebiotics

Prebiotics, non-digestible food ingredients such as oligosaccharides, are known to promote a healthy microbiome in humans. We are characterising the ability of beneficial bifido- and lacto-bacteria to utilise selected prebiotic carbohydrate substrates.

References

In vitro fermentation of prebiotic oligosaccharides by Bifidobacterium lactis HN019 and Lactobacillus spp., Anaerobe (2014).

RNA-stable-isotope probing shows utilization of carbon from inulin by specific bacterial populations in the rat large bowel, Applied and Environmental Microbiology (2014).

Lactobacillus reuteri 100-23 modulates urea hydrolysis in the murine stomach, Applied and Environmental Microbiology (2014).

Foods for health

We provide the carbohydrate analysis component of the Foods for Health multi-disciplinary research programme, funded by the Ministry for Business, Innovation and Employment and led by Plant & Food Research.

The programme is taking a holistic approach towards understanding the impact of selected dietary fibres on human health. Research is focussed in the following areas:

  • the metabolic behaviour of the microbiome
  • changes to complex carbohydrates during digestion
  • the presence or absence of various carbohydrate-degrading enzymes
  • the downstream immune effects.

These effects are being studied across a set of individuals. We have already observed very different responses between people as well as dramatic changes in an individual during trials.

References

Effects of simulated digestion in vitro on cell wall polysaccharides of kiwifruit (Actinidia spp.), Food Chemistry(2012).

Characterizing kiwifruit carbohydrate utilisation in vitro and its consequences for human faecal microbiota, Journal of Proteome Research (2012).

Bifidobacteria and the immune system

The gastrointestinal tract of a normal human foetus is sterile but is rapidly colonised by bacteria from the mother and the surrounding environment after birth. Beneficial bacteria, particularly bifidobacteria, are known to play a key role in the development of a normal immune system.

These bacteria ‘educate’ the developing immune system as it samples the carbohydrate-based structures on their surfaces. The presence of these bacteria eventually causes individuals to be less susceptible to allergens or atopic disease (asthma, eczema, hayfever) throughout their lives.

By analysing the polysaccharides and glycolipids on the surface of the bacteria, we have identified novel structures that may play a role in directing the immune system towards a tolerant, rather than allergic, phenotype.

We are currently working with Dr Elizabeth Forbes-Blom on animal models to determine the role of glycolipids and other surface components from gut bacteria in the allergic immune response.

Reference

Discovery of lipids from B. longum subsp. infantis using whole cell MALDI analysis, Journal of Organic Chemistry(2014).

Seaweed polysaccharides

Our team has made a significant contribution to the study of seaweed polysaccharides in research programmes spanning 30 years. In particular, we have refined the extraction, characterisation and uses of the agars and carrageenans from red seaweeds, and the alginates and fucoidans from brown seaweeds. Many of these polysaccharides have major commercial applications in the food and drug industries.

We developed improved chemical and spectroscopic methods that continue to be widely applied in academia and industry, and we regularly provide analytical and process development services under contract.

References

Activity of polysaccharides from brown seaweeds against herpes simplex virus type 1, and possible relevance to the treatment of Alzheimer's disease, International Journal of Biological Macromolecules (2015).

Chemical methods for the analysis of sulphated galactans from red algae, Carbohydrate Research (1991).

New analysis technologies

Identifying the structures of complex carbohydrates is challenging and new methodology is still required.

We have recently had success in the development of:

  • A quantitative capillary electrophoresis method for the analysis of disaccharide constituents of heparan sulfate.
  • HPLC methods using CAD (coronal aerosol discharge) detection to identify the potency and impurities of complex synthetic glycolipids and synthetic cancer vaccine components and to monitor their stability.

References

Engineering a vascular endothelial growth factor 165-binding heparan sulfate for vascular therapy, Biomaterials (2014).

Structure of a shear-thickening polysaccharide extracted from the New Zealand black tree fern,Cyathea medullaris, International Journal of Biological Macromolecules (2014).