13TSB_N4L2: CELLDEX - Development of a low calorie bulk sugar replacer
Lead Research Organisation:
University of Aberdeen
Department Name: Rowett Institute of Nutrition and Health
Abstract
The Microbiology Group at RINH (U. Aberdeen) will perform a key element (WP3.1- "Assessment of cellodextrin
fermentability by human colonic bacteria in vitro") of Work package 3 within the TSB project CELLDEX. They will use in
vitro approaches to assess the fermentability of cellodextrins by human intestinal microorganisms and to predict the likely
impact of cellodextrins upon microbial community composition and metabolic outputs. Cellodextrins will be incubated with
mixed human faecal microbiota under anaerobic conditions using batch cultures and pH-controlled continuous flow
fermentor models. Molecular approaches will be used to monitor changes in microbial community composition. The major
products of fermentation, short chain fatty acids and gases, will be monitored by gas chromatography and cellodextrin
utilization will be monitored by analysis of total sugars. The ability of a range of dominant polysaccharide-utilizing
anaerobes that have been isolated in our laboratory from from the human colon to grow with cellodextrins as a sole energy
source will also be assessed here. Together with the results from molecular community analysis, this should provide
information on species likely to be responsible for cellodextrin utilization. This work will precede and inform the planned
human dietary intervention studies to be performed by University of Nottingham.
fermentability by human colonic bacteria in vitro") of Work package 3 within the TSB project CELLDEX. They will use in
vitro approaches to assess the fermentability of cellodextrins by human intestinal microorganisms and to predict the likely
impact of cellodextrins upon microbial community composition and metabolic outputs. Cellodextrins will be incubated with
mixed human faecal microbiota under anaerobic conditions using batch cultures and pH-controlled continuous flow
fermentor models. Molecular approaches will be used to monitor changes in microbial community composition. The major
products of fermentation, short chain fatty acids and gases, will be monitored by gas chromatography and cellodextrin
utilization will be monitored by analysis of total sugars. The ability of a range of dominant polysaccharide-utilizing
anaerobes that have been isolated in our laboratory from from the human colon to grow with cellodextrins as a sole energy
source will also be assessed here. Together with the results from molecular community analysis, this should provide
information on species likely to be responsible for cellodextrin utilization. This work will precede and inform the planned
human dietary intervention studies to be performed by University of Nottingham.
Technical Summary
Technical Summary
The TSB project CELLDEX will investigate whether cellodextrins can be used as sugar replacers in certain human foodstuffs. Cellodextrins are beta (1-4) linked glucose polymers (the same primary structure as in cellulose) that cannot be degraded by human digestive enzymes. They will therefore arrive in the large intestine where they may be subject to microbial fermentation. The purpose of this part of the project (WP3.1) is to determine the likely rate and extent of such fermentation using in vitro approaches, and to predict the likely impact of cellodextrins upon microbial community composition and metabolic outputs. Cellodextrins will be provided as the sole added energy source to batch cultures of anaerobic medium (prepared under 100% CO2) inoculated with human faecal microbiota, and the resulting fermentation compared with that of replicate cultures provided with cellulose or soluble starch. Continuous flow fermentor models may also be employed to investigate the effect of pH on the fermentation. Microbial community composition will be monitored for the inoculum and after 48h incubation by qPCR, using a panel of primers developed by the RINH Microbiology group. High throughput sequencing of 16S rRNA amplicons using signature tagged primers may also be applied if required to obtain more detailed information. The major products of fermentation, short chain fatty acids and gases, will be monitored by gas chromatography and cellodextrin utilization will be monitored by the analysis of total sugars. Genome sequences are available for a range of dominant polysaccharide-utilizing anaerobes that have been isolated in our laboratory from the human colon. Those possessing candidate cellulase genes will be tested for their ability to grow with cellodextrins as a sole energy source.
The TSB project CELLDEX will investigate whether cellodextrins can be used as sugar replacers in certain human foodstuffs. Cellodextrins are beta (1-4) linked glucose polymers (the same primary structure as in cellulose) that cannot be degraded by human digestive enzymes. They will therefore arrive in the large intestine where they may be subject to microbial fermentation. The purpose of this part of the project (WP3.1) is to determine the likely rate and extent of such fermentation using in vitro approaches, and to predict the likely impact of cellodextrins upon microbial community composition and metabolic outputs. Cellodextrins will be provided as the sole added energy source to batch cultures of anaerobic medium (prepared under 100% CO2) inoculated with human faecal microbiota, and the resulting fermentation compared with that of replicate cultures provided with cellulose or soluble starch. Continuous flow fermentor models may also be employed to investigate the effect of pH on the fermentation. Microbial community composition will be monitored for the inoculum and after 48h incubation by qPCR, using a panel of primers developed by the RINH Microbiology group. High throughput sequencing of 16S rRNA amplicons using signature tagged primers may also be applied if required to obtain more detailed information. The major products of fermentation, short chain fatty acids and gases, will be monitored by gas chromatography and cellodextrin utilization will be monitored by the analysis of total sugars. Genome sequences are available for a range of dominant polysaccharide-utilizing anaerobes that have been isolated in our laboratory from the human colon. Those possessing candidate cellulase genes will be tested for their ability to grow with cellodextrins as a sole energy source.
Planned Impact
The long term potential impact of this work is to benefit public health by providing a safe and acceptable bulk sugar
replacer that might be used in a variety of foodstuffs. Such products can play an important role in combating obesity and
diabetes in the UK population by helping people to decrease their dietary intake of sugars and total energy. By assessing
the fermentability of cellodextrins, we will be helping to establish acceptable levels of intake that avoid possible problems
due to microbial activity in the large intestine. The work will of course benefit the food producer by allowing them to
introduce lower calorie alternatives to existing products and therefore to market new products for the weight-conscious
customer. Cellodextrins can be derived by enzymatic and/or chemical action from waste biomass and therefore represent
an environmentally sustainable solution.
replacer that might be used in a variety of foodstuffs. Such products can play an important role in combating obesity and
diabetes in the UK population by helping people to decrease their dietary intake of sugars and total energy. By assessing
the fermentability of cellodextrins, we will be helping to establish acceptable levels of intake that avoid possible problems
due to microbial activity in the large intestine. The work will of course benefit the food producer by allowing them to
introduce lower calorie alternatives to existing products and therefore to market new products for the weight-conscious
customer. Cellodextrins can be derived by enzymatic and/or chemical action from waste biomass and therefore represent
an environmentally sustainable solution.
People |
ORCID iD |
| Harry Flint (Principal Investigator) | |
| Petra Louis (Co-Investigator) |
| Description | 1. We have shown that certain bacterial species found in the healthy human intestine have the ability to use short chains of 5 or 6 glucose residues derived from cellulose as source of energy for growth. This ability was found in 7 out of 9 strains of fibre-degrading bacteria that we tested in pure culture (ie. as isolated bacterial strains). 2. We also investigated the ability of mixed human gut bacteria (from faecal samples) to ferment cellulose-related carbohydrates. We found that this activity was critically dependent on the volunteer who donated the faecal sample, with one out of 4 donors tested giving rise to fermentation of fibrillar cellulose. 3. The conclusion is that while beta-(1,4)-linked glucose chains (as found in cellulose) are totally non-digestible by human enzymes, there is some capacity for them to be degraded in the human intestine, at least in some individuals. The consequences of intestinal fermentation (production of acids, gas) must therefore be considered if they are to be used as sugar replacers. |
| Exploitation Route | These findings are being used by our partners in the Celldex consortium in the later stages of this project. |
| Sectors | Agriculture, Food and Drink,Healthcare |