## 4 Discussion  
Overall, all four of the products tested resulted in an increase in SCFAs for the treatment period versus the control period. This was generally true for both donors, though there were some exceptions, likely the result of donor specific differences in baseline microbial community composition. The test products had little effect on lactate levels. Ammonium and bSCFA levels were also significantly increased in the treatment versus control period in the PC and DC compartments for all test products and both donors. All test products resulted in a significant increase in the Simpson diversity index in the treatment versus control periods in the luminal PC, supplementation with the LCM resulted in a significant increase for both the luminal and mucosal DC, and supplementation with the other three test products resulted in a significant increase in the mucosal PC. The significant increase in SCFAs in both the PC and DC is noteworthy, as it indicates that the test products are being fermented in both compartments. The propiogenic response was significantly stronger with the GoodBiome(tm) Foods products than with the comparator, indicating that the addition of prebiotics and _B. subtilis_ HU58 may be responsible for the increased propiogenic response. This response was strongest for donor A with the OSM product and for donor B with the LCM product. Although all test products resulted in increased acetate production, the OSM had the strongest overall effect. In donor A, an increase in butyrate was observed for all test products with the largest increase in butyrate production occurring with the OSM; butyrate production was only significantly increased with KC for donor B. Increased microbial diversity in the human gut is generally considered beneficial. For example, a recent study in humans reported that long term weight gain was associated with a significantly lower Simpson diversity index compared with individuals who did not experience long term weight gain [47]. Dietary fiber intake was also associated with less weight gain. Another study found that higher \(\alpha\) diversity in the gut microbiome, along with more butyrate-producing species, were associated with a lower incidence of type 2 diabetes and lower rates of insulin resistance among non-diabetic individuals [48]. Therefore, we consider the increase in the Simpson diversity index observed with the test products in this in vitro model to be encouraging regarding their potential to impart beneficial effects on the human gut. The significant increase in Proteobacteria levels in the PC for both donors and with all test products indicates the involvement of this phylum in the primary fermentation of these products. The increase in Proteobacteria was largely due to an increase in the  
Figure 4: Changes in microbial community composition (relative abundance) at the family level in the luminal PC and DC for (**A**) Donor A, luminal PC; (**B**) Donor B, luminal PC; (**C**) Donor A, luminal DC; (**D**) Donor B, luminal DC. * Unidentified family. BBM = Berry Blast Muffin; C = control period; DC = distal colon; KC = Kodiak Cake; LCM = Lemon Chia Muffin; OSM = Oat Spice Mookie; PC = proximal colon; TR = treatment period. Enterobacteriaceae_ family. While _Enterobacteriaceae_ are present both as resident and transient members of the healthy human microbiome [49; 50], they are considered symbionts and have the potential to be harmful as some members of this family are pathogenic. Therefore, the potential negative health effects of an increase in _Enterobacteriaceae_ must be taken into consideration and addressed in future studies. While the Bacteroidetes phylum did not increase significantly, there were changes in the microbial composition at the family level. At the expense of _Bacteroidaceae_, enrichment was observed for _Rikenelaceae_ and _Tannerelaceae_, which are a group of primary substrate degraders that produce mainly succinate and acetate [51].