# Production of Sustainable Postbiotics from Sugarcane Straw for Potential Food Applications
## 3 Results and Discussion
### Impact of Postbiotics on Gut Microbiota Modulation
One to three molecules of fructose bonded directly to the fructose residue of sucrose with 8-1,2 linkage form the non-digestible oligosaccharide known as FOS. Short-chain fatty acids including acetic, propionic, and n-butyric acids, carbon dioxide, hydrogen, methane, amino acids, and vitamins are produced during the fermentation of FOS by the gut bacteria. The increase in SCFA decreases the pH, which is favorable for _Bifidobacterium_ and _Lactobacillus_ growth, while it suppresses the pathogenic bacteria [78], also seen in this work (Figure 4). Prebiotics primarily target strains of _Lactobacillus_ and _Bifidobacterium_, among others, which can combat chronic diseases because intestinal fermentation generates SCFAs. They are produced as a byproduct of the intestinal microbiota's metabolism, primarily from dietary fiber that is not digestible [79]. Figure 5 shows the values obtained for SCFA in the cultures. Figure 5: Concentration (mM) of the short-chain fatty acids (SCFA) and lactate produced for 48 h of human colonic fermentation using straw extract obtained after fermentation with _S. cerevisiae_. Inoculum control (IC, \(\blacksquare\)), fructose-oligosaccharides (FOS, \(\blacksquare\)), and straw extract after fermentation with _S. cerevisiae_ (\(\blacksquare\)). a,b,c,d Significant variations (\(p\) < 0.05) between samples for each acid are denoted by different letters. Without the interference of a nutritional source, the IC gives background data on the intrinsic and established gut microbiota metabolite production. As expected, the IC has the lowest SCFA production because there is no additional substrate to feed the intestinal bacteria. After FOS administration, an increase in SCFA production was observed. Thus, the administration of prebiotics induces the synthesis of SCFA, which has been reported to exert positive effects against the inflammatory behavior of the intestinal barrier. According to these findings, prebiotics not only aid in the growth and development of particular colonic bacteria but also encourage the synthesis of bacterial metabolites that may have positive health effects [80]. The acetate was the main SCFA quantified in all samples after 48 h fermentation (\(p<0.05\)) when compared with negative and positive controls. The last two increased along fermentation time but to a lower extent. Fermentation for 24 h was enough for the maximum content of acetate, showing an increase from 21.6 to 69.3 mM. According to reports, this material is the most common substance in the large intestine and the main consequence of bifidobacterial fermentation in a human fecal environment [81; 82]. The abundance of acetate is crucial for reducing inflammation and blocking pathogen invasion such as Enterohaemorrhagic _Escherichia coli_[83; 84]. Lactate increased significantly in the presence of FOS, but no differences were observed in negative control or in the presence of straw extract. Butyrate increased along fermentation for all conditions tested, but the increase observed was higher when fermentation occurred in the presence of straw extract, presenting 9.94 mM by comparison with FOS, which only had 3.6 mM after 48 h. Several in vitro investigations have shown that butyrate can cause apoptosis in colonic tumor cell lines, and it is thought that butyrate is a beneficial metabolite of gut bacterial activity [85]. Butyrate formation occurs in certain Firmicutes bacteria, through two mechanisms, one via butyrate kinase and another by butyric acetate CoA transferase [86]. Butyric acid has beneficial effects on the intestinal mucosa and influences cell development, making it crucial for human health. It has anti-inflammatory qualities and lowers the likelihood of developing colon cancer [87; 81]. Colitis treatment options have also included butyrate irrigation (enema). As a result, substances that stimulate the formation of butyrate at intestinal epithelial cells are of interest to the food industry supplements.