The prebiotic effect is a fundamental concept in the fields of nutrition and gut health, referring to the beneficial effects of specific non-digestible dietary components on the gut microbiota, including xylooligosaccharides (XOS). These compounds function as food sources for beneficial gut bacteria, fostering their growth and activity. In this work, in vitro studies were performed to evaluate the
prebiotic potential of XOS produced from olive stones (OS) and coffee silver skin (CSS) via a onestep fermentation using a recombinant Bacillus subtilis 3610 harbouring the xylanase gene xyn2 from Trichoderma reesei. This potential was compared with a commercially available prebiotic oligofructose (Orafti®, BENEO, Germany). A mixture of human faeces from four healthy donors aged between 24 and 28 years old was used as inoculum. The pH variation and the production of short-chain fatty acids (SCFAs), gases, and ammonia were analysed during the 48 hours
fermentations. The prebiotic supplementation resulted in a reduction of the pH value over time, with oligofructose presenting the most significant pH drop at 48 hours (pH=3.65). The addition of prebiotics also significantly increased the production of beneficial SCFAs, with oligofrutose exhibiting a notable increase in the production of lactic and acetic acid production after 48 hours (28.0±0.1 and 28±1 mM, respectively), while OS-XOS and CSS-XOS demonstrated a more prominent rise towards the production of acetic acid (14.8±0.4 and 20.4±0.1 mM, respectively), butyric acid (2.5±0.3 and 3.29±0.04 mM, respectively), and valeric acid (75±1 and 110±14 mM, respectively) at 48 hours. Remarkably, the gas analysis revealed that the addition of OS/CSS-XOS fully suppressed the production of CH4 and increased the CO2 generation after 48 hours (2.6±0.7 and 5.20±0.05 mmol.L-1medium, respectively). These findings strongly suggest that the XOS produced from OS and CSS holds potential prebiotic properties for human health.CA, AC and JS acknowledge the junior researcher contract (CEECIND/00293/2020) and the PhD
scholarships (UI/BD/153689/2022 and 2022.11695.BD), respectively, from the Portuguese
Foundation of Science and Technology (FCT). This study was supported by FCT under the scope of the strategic funding of CIMO (UIDB/00690/2020 and UIDP/00690/2020), CEB
(UIDB/04469/2020) and Associate Laboratory SusTEC (LA/P/0007/2020).info:eu-repo/semantics/publishedVersio
