Introduction: Understanding the intricate interactions occurring within the gut microbiome and unravelling its impact on human health is a challenging task. Invasive strategies, such as endoscopy and nasoenteric probes that allow direct sampling of the gut environment, face practical and ethical limitations. Bioreactors are in vitro models used to overcome some of these limitations, which have contributed to our understanding of gut microbial ecology by providing controlled environments that mimic some of the features of the gastrointestinal tract.
Objectives: This work aims to develop a single-stage bioreactor to simulate selected conditions of the ascending colon.
Methods: All the experiments were performed in a Bio-Book Compact bioreactor. The conditions selected for the system were: temperature, 37 °C; pH, 6.8; hydraulic retention time, 12 h; and a working volume of 250 mL. A fresh stool sample from a 30-year-old healthy donor was used as inoculum, and a culture medium mimicking the nutrients available in the colon was used as feedstock. Anaerobic conditions were first established by purging the culture vessel with high-purity Argon during inoculation, and after this step, the microbial community sustained the anaerobic environment. The cultivation was run for a total of 9 days. 16s rRNA amplicon sequencing was used to characterize the microbial communities growing in the bioreactor, and proton nuclear magnetic resonance (1H NMR) experiments were performed for metabolic profiling.
Results: The bioreactor provided a suitable environment for the growth of a diverse microbial community, which sustained a low pO2 between 2 - 2.5 mbar and an oxidative redox potential (ORP) of -510 mV at the steady state. 1H NMR metabolic profiling enabled the putative identification of 20 metabolites. Microbial functionality markers such as dissolved oxygen, ORP, and short-chain fatty acids indicate functional stability after 3 days of cultivation. Moreover, we observed an enrichment of Blautia over Faecalibacterium in the system compared to the faecal inoculum.
Conclusion: Our single-stage bioreactor could sustain a functionally stable microbial community obtained from stool samples. This model is a valuable asset for future investigations aiming to unravel the complexities of microbial communities in the human gut.