# Production of Sustainable Postbiotics from Sugarcane Straw for Potential Food Applications
## 3 Results and Discussion
### Impact of Postbiotics on Gut Microbiota Modulation  
The effect of the extract in gut microbiota, an in vitro fermentation model was performed using feces from five donors. Fermentation sampling was performed at times 0, 24, and 48 h, to quantify the pH, the total and specific bacteria, such as _Enterobacteriaceae_, lactic \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Analysis**} & \multicolumn{2}{c}{**Non-Fermented**} & \multicolumn{2}{c}{**Fermented Straw**} \\  & & **Straw Extract** & **Extract** \\ \hline \multirow{3}{*}{Antioxidant activity} & ABTS IC\({}_{50}\) (mg/mL) & 7.34 \(\pm\) 0.34  \\  & DPPH IC\({}_{50}\) (mg/mL) & 13.08 \(\pm\) 0.34  \\  & ORAC (μmol TE/g) & 171.21 \(\pm\) 11.27  \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Antioxidant capacity of sugarcane straw extract after cellulose saccharification with and without (control) _S. cerevisiae_ fermentation. acid bacteria, and _Bifidobacterium_, and finally the short-chain fatty acids (SCFA). Obtained data were compared with two controls, one positive prebiotic designated as FOS and one negative only with inoculum control (IC). The use of FOS was for control of the impact on gut modulation in terms of microorganisms composition, in the evaluation of the main beneficial bacteria such as _Lactobacillus_ and _Bifidobacterium_. The common pH of the human colon varies between 6.0 and 8.0 [77], and in the negative control (IC), no significant differences (\(p>0.05\)) were observed after 48 h. On the other hand, FOS presented a high decrease from 7.15 to 3.64, and in the straw extract, pH decreased from 7.24 to 6.72 (Figure 3). The pH decrease, although slight, may create a favorable environment for the reproduction of some beneficial bacteria while inhibiting harmful microorganisms. The fermented straw extract as well as FOS used as the positive control and no extract addition as negative control were tested and were incubated for 48 h with fecal bacteria. Figure 4 depicts modifications in bacterial populations following this therapy. Figure 4: Changes in bacterial viable cell counts (log CFU/mL) in batch cultures after 48 h at 37 \({}^{\circ}\)C of inoculation of different substrates. Inoculum control (IC, #), fructose-oligosaccharides (FOS, #), and straw extract after fermentation with _S. cerevisiae_ (#). \({}^{\text{a,b,c,d,e}}\) Different letters mean statically significant (\(p<0.05\)) differences between samples. Figure 3: The changes in pH value of simulated gut microbiota fermentation (five donors) along 48 h in the presence of inoculum control that represents media with only fecal inoculum (IC, #), fructoligosaccharides (FOS, #), and straw extract after fermentation with _S. cerevisiae_ (#). \({}^{\text{a,b,c,d,e,f}}\) Different letters mean significant differences (\(p<0.05\)) between samples. After 24 or 48 hours of fermentation, no significant changes (p > 0.05) in the total number of bacteria were found, presenting a value of 8 log (CFU/mL) over the 48 h.  
In lactic acid bacteria (LAB), no significant differences (\(p\) > 0.05) were seen along fermentation time in the inoculums with straw extract or in the negative control. On the other side, the positive control (FOS) increased from 5.2 to 8.0 log (CFU/mL) after 48 h. _Bifidobacterium_, where no extract was added, presented a decrease by the end of 48 h, while in the positive control, the presence of FOS stimulated this group of bacteria to increase from 7.3 to 7.9 log (CFU/mL), and in the presence of straw extract, the group decreased (\(p\) < 0.05) from 7.3 to 6.0 log (CFU/mL). The group of _Enterobacteriaceae_ cells were not detected in positive controls after 24 and 48 h fermentation, while in the negative control and in the presence of straw extract, the group decreased significantly only after 48 h fermentation, from 5.5 to 3.5 log (CFU/mL). The inoculum with FOS was the only one that promoted the growth of LAB and bifidobacteria, and this was due to its prebiotic capacity.