Hi BioStars Community,

I want to put a detailed theoretical concept out into the open to see if any computational biology labs or iGEM teams are interested in modeling it. Just to be completely clear up front: this is a purely hypothetical thought experiment, not a completed project with existing data. I am simply sharing the blueprint in hopes that someone might find the premise worth simulating.

The Core Idea Could we use synthetic biology to give humans the ability to digest plant cellulose? Specifically, I want to explore modeling the introduction of a heterologous, crystalline-capable cellulase enzyme system into a dominant, human-native gut bacterium.

How It Would Work (The Blueprint)

1. The Target Bacteria: We would use Bacteroides thetaiotaomicron (B. thetaiotaomicron). It is a dominant, highly stable colonizer of the human large intestine that already has advanced Polysaccharide Utilization Loci (PULs) built for complex carbohydrate digestion.
2. The Enzyme Source: The genetic code for the cellulase enzymes would be borrowed from highly efficient natural digesters, like the ruminant bacterium Fibrobacter succinogenes or the fungus Trichoderma reesei.
3. The Delivery System: To physically get the engineered bacteria into the human digestive tract, they would be freeze-dried and placed inside an enteric-coated oral capsule. This specialized coating protects the bacteria from being destroyed by harsh stomach acid. The capsule is designed to dissolve only when it hits the higher pH environment of the lower small intestine, releasing the live bacteria right at the gateway to the colon so they can safely integrate into the native microbiome.
4. The Surface-Display Mechanism: Instead of simple intracellular expression, the model would need to feature a surface-display system. The cellulase enzymes must anchor to the outer membrane of B. thetaiotaomicron so they can physically degrade crystalline cellulose on contact within the colonic lumen.

The Therapeutic Value While the idea of digesting plant matter is fascinating on its own, I hypothesize that this system could actually serve as a powerful, localized medical therapeutic:

• Metabolic and Weight Regulation: The bacteria would consume the resulting glucose for themselves, but they would excrete a massive volume of Short-Chain Fatty Acids (SCFAs)—specifically acetate and propionate—into the human bloodstream. This could trigger a heavy, natural release of GLP-1 and PYY satiety hormones, acting as a built-in biological tool to manage appetite and obesity.
• Targeted Gut Healing: The continuous fermentation process would release a steady supply of butyrate directly onto the colon lining, creating a powerful anti-inflammatory shield that could help manage or prevent IBD and Ulcerative Colitis.

The Big Bottleneck (Where I need your thoughts) If a team were to simulate this, how would the genomic model handle the massive byproducts of CO2 and methane gas? To prevent severe patient bloating and discomfort, would we need to model a co-cultured, syntrophic strain (like a methanogen) alongside it to consume the gas?

I am dropping this framework into the public domain for anyone looking for a unique metabolic modeling project. I would love to hear your thoughts on whether engineering this specific surface-display system is even genomically feasible!

Sincerly,

Nicholas Joel Vallverdu