278. Comparing Human and Canine in vitro Digestibility and Colonic Fermentation of Yeast-based Protein.

Abstract Introduction Yeast-based proteins (YBP) represent a sustainable alternative protein source for both human and animal nutrition. However, digestive physiology, such as GI transit time, body temperature and enzyme profile, differs significantly between humans and dogs, potentially affecting protein utilization. Due to these differences, results obtained from human studies cannot be directly extrapolated for the companion animal market. This study aimed to compare the digestibility of a yeast-based protein in human and canine digestive systems and evaluate its colonic fermentation patterns using in vitro models. Animals, materials and methods YBP digestibility was assessed using the TIM-1 [1] or TIM-1 FIDO [2] dynamic in vitro digestion system adapted for human or dog physiological conditions, with key differences in temperature, enzymes and gastric emptying curve (n = 3). Both mimic the upper gastrointestinal tract, including stomach and small intestinal compartments. Samples were collected hourly (5h for human and 6h for dog in total) from jejunum and ileum dialysate, and ileal effluent. Nitrogen content was analysed using Dumas method. For colonic fermentation assessment, the Colon-on-a-plate® technology (ProDigest, [3]) was used using individual faecal inoculum from 6 healthy adult humans (age and gender balanced) or 6 healthy dogs (n = 6, age and gender balanced). Fermentation parameters measured included short-chain fatty acid production, gas composition, and gut metabolite profiling using uHPLC-HRMS for relative quantification of 230 metabolites. Two-way ANOVA (canine vs human) was used to compare the differences between species for each read-out, followed by a Bonferroni multiple comparison analysis. Results and discussion YBP digestibility results showed species-specific differences in protein absorption kinetics, where the human digestion resulted in a faster jejunum and ileum nitrogen bioaccessibility compared to dog with respectively 77.8±2.4% (human, 5-hour digestion) and 75.9±2.7% (dog, 6-hour digestion) bioaccessible nitrogen compared to intake (p > 0.05). Overall, the total nitrogen bioaccessibility was comparable between the species (p > 0.05). The colonic fermentation results highlight differences between human and dog microbial activity, where the focus lies on the undigestible fraction of the yeast-based protein, mainly consisting of fibres like β-glucans and mannans. Conclusion This study assessed the differences in the kinetics of yeast protein digestion and the impact on colonic fermentation parameters between humans and dogs. Species-specific physiological differences impact digestibility and microbial metabolites and composition, which can be of importance when formulating alternative proteins in various applications. These results provide insights for optimizing nutritional formulations for both human and companion animals, potentially improving digestibility, colonic microbial health, and overall well-being. In vivo follow-up is recommended to assess the nutritional impact of YBP in dogs. References: [1] Verhoeckx et al (2015) Springer, Chapter 5, [2] Smeets-Peeters et al (1999) Alternatives to Laboratory Animals, 27(6), 935-949, [3] Perreau et al (2023) Nutrients, 15(19).