# Production of Sustainable Postbiotics from Sugarcane Straw for Potential Food Applications
## 3 Results and Discussion
### Phenolic Compounds Profile
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Proposed Name** & **Concentration** \\  & **(\(\mu\)g/g Dry Extract)** & **(\(\mu\)g/g Dry Extract)** \\ \hline  & **Non-Fermented Straw** & **Fermented Straw** \\  & **Extract** & **Extract** \\ \hline Protocatechuic acid & 2.75 \(\pm\) 0.55 b  & 3.81 \(\pm\) 0.59 a  \\
2,5-Dihydroxybenzoic acid isomer 1 & 0.93 \(\pm\) 1.82 a  \\
2,5-Dihydroxybenzoic acid isomer 2 & 24.56 \(\pm\) 4.35 a  & 20.58 \(\pm\) 0.28 a  \\
4-Hydroxybenzoic acid acid & 1.97 \(\pm\) 0.10 a  & 1.38 \(\pm\) 0.02 a  \\
3,4-Dihydroxybenzaldehyde & 7.17 \(\pm\) 0.21 b  & 24.82 \(\pm\) 0.04 a  \\
4-Hydroxybenzaldehyde & 17.71 \(\pm\) 0.17 a  \\
5-O-Feruloylquinic acid & 8.39 \(\pm\) 0.05 a study. Most of the reports in the literature described phenolic extractions using organic solvents such as ethanol [47], but in this work, the solvent used was water, and the extract went through a sterilization process before the saccharification process. The exposure of the extract to high temperature and low pressure (121 \({}^{\circ}\)C, 10 min 1.1 atm) applied for sterilization may has been responsible for the lower content of polyphenols detected in this extract [48]. The aqueous environment was not favorable for flavonoids in the extract, since sugarcane straw is characterized by the presence of several compounds such as luteolin and apigenin with moieties of glucose or arabinoside and O-glycosylated or the presence of tricin and luteolin aglycone [49; 50]. Within hydroxybenzoic acids, six distinct compounds were found, and the two most representative were 2,5-dihydroxybenzoic acid isomer 2 (24.56 \(\pm\) 4.35 \(\upmu\)g/g dw) and 4-hydroxybenzaldehyde (17.71 \(\pm\) 0.17 \(\upmu\)g/g dw), with the ions \(m/z\) 153 [M \(-\) H]\({}^{-}\) (C\({}_{7}\)H\({}_{5}\)O\({}_{4}\)) and \(m/z\) 121 [M \(-\) H]\({}^{-}\) (C\({}_{7}\)H\({}_{5}\)O\({}_{2}\)), respectively. Around 27% of the extract's measured components fall into this category. High levels have been linked to systemic infections. Hydroxybenzoic acid derivatives are in charge for plants' defense response against pathogens [51]. In addition to serving plant purposes, they also possess intriguing biological characteristics that make them appealing to the food business. 2,5-Dihydroxybenzoic acid has shown interesting bioactive properties such as antidiabetic potential [52]. After yeast fermentation, the content of all the compounds within this class decreased except for 3,4-dihydroxybenzaldehyde, which increased from 7.17 to 24.82 \(\upmu\)g/g dw. 3,4-dihydroxybenzaldehyde is known to be covalently linked to cell wall polysaccharides, and during yeast fermentation, there may occur a release of these compounds from polysaccharides that are more accessible to quantify. Similar results were reported for sorghum fermented with a lactic bacteria [53]. Hydroscinamic acids were the predominant class representing 71% of whole-extract composition. The presence of quinic acid esterified with ferulic acid units was detected in four compounds. Additionally, free ferulic and \(p\)-coumaric acids were detected. Ferulic acid promotes the development of lignin in mature cane, making it a molecular marker that changes with genotypes, cell types, and tissues within the same plant [54]. Immunomodulatory effect by ferulic and \(p\)-coumaric acids has been reported due to its antioxidant capacity that exerts a cytoprotective effect [55]. Ferulic acid (\(m/z\) 193 [M \(-\) H]\({}^{-}\) (C\({}_{10}\)H\({}_{9}\)O\({}_{4}\))) was present in higher quantities with 110.36 \(\pm\) 0.01 \(\upmu\)g/g dw. After yeast fermentation, the only hydroxycinamic acid that decreased was ferulic acid, by ca. 39%. The remaining compounds did not present a significant variation (Table 3). _Saccharomyces cerevisiae_ growth may be inhibited by some phenolic compounds, and to overcome this issue, certain phenolic compounds can be catabolized and metabolically processed in situ by yeast.