Bacteria produce a variety of different compounds that are expressed on their surface or secreted to their surroundings. A large share of these compounds are different types of carbohydrates that play a number of different biological roles. Some of these carbohydrates are called “exopolysaccharides” (EPS) and is what make some bacteria very slimy and slippery. EPS play several important roles for both bacteria and humans. For example, bacterial pathogens use EPS to create biofilms to protect themselves from the immune system or antibiotics. Further, many food-related bacteria secrete carbohydrates that contribute with important properties such as texture and stabilizers in food. Finally, when bacteria are in complex communities like in the gastrointestinal environment, EPS can act as signaling entities between bacteria, between bacteria and the host, or serve as nutrient sources for other bacteria. Surprisingly, very little is known about how EPS are degraded by bacteria and their enzymes.
In this project we want to learn more about EPS, how these complex carbohydrates are degraded by bacteria and how we can use EPS in new food and health applications. By utilizing an on-site biorefinery, large amounts of pure EPS from several cornerstone bacteria will be produced and subsequently used as nutrient sources in bacterial cultivation screens. By analyzing the enzyme systems of the EPS-degrading bacteria, we will identify and obtain enzymes used for EPS-degradation. By treating the EPS we produce with EPS modifying enzymes and additional chemical methods, we will be able to make completely new compounds that can be used for many different purposes, for example to alter the composition of the gut microbiota (from unhealthy to healthy), to create new food based EPS for texture and taste and last but not least, create novel antimicrobial compounds.
Bacterial exopolysaccharides (EPS) represent a highly diverse group of biopolymers that are secreted by bacteria. Whereas hundreds of EPS structures have been characterized, few studies exist that have investigated EPS degradation and the enzymes involved. Due to the enormous diversity of EPS molecules, we thus hypothesize that there is a large gap in knowledge of EPS degrading and modifying enzymes. In the present project we will tap into this large reservoir of unexplored enzymes to increase our general understanding of EPS utilization in biological systems and, through an interdisciplinary effort, harness the acquired knowledge to generate novel biotechnological tools and applications. By utilizing an on-site biorefinery, multi-gram amounts of pure EPS from several bacteria will be produced and subsequently used as nutrient sources in bacterial cultivation screens. Here, an expected important outcome is knowledge on how EPS can alter the composition of the gut microbiota. By analysis of EPS degrading isolates or enrichment cultures by a combination of genomics and proteomics, enzymes involved in EPS degradation will be identified and subsequently cloned, expressed and characterized to reveal complete degradation pathways. These pathways are likely to contain multiple new enzyme families and activities. The characterized enzymes represent an EPS toolbox that will allow tailoring of EPS-oligosaccharides, that, by means of chemical synthesis, will be used to generate fluorescent glycoconjugates (e.g. fluorescent glyco-carbon dots) that in turn can be used to identify EPS-binding or degrading bacteria in complex microbial communities. Using the same chemical approach, novel antimicrobial compounds will be synthesized to specifically target EPS degrading pathogens identified earlier in the project timeline. Finally, EPSs and EPS-oligosaccharides will be screened for their immunomodulatory properties to unravel potential EPS-host interactions.