## 3 Results and Discussion
### Prebiotic Potential
In the same way, an in vitro experimentation on _Bifidobacterium_ strains showed a higher biomass yield during fermentation using short chains FOS in comparison with longer FOS [51]. Furthermore, in their study, [PERSON] et al. [13] used a partial hydrolysis of pectin polysaccharide to improve their bifidogenic properties. They demonstrated that pectin oligosaccharides possess a better prebiotic activity than the complex pectin molecule, although their bifidogenic effect was lower compared to FOS. The prebiotic activity of PWPs and PLM was confirmed by lower pH values and higher organic acid concentrations during the fermentation of _Lactobacillus_ strains (Table 3). After 20 h of fermentation the bacteria acidified the initial pH of PWPs (pH = 6.55 at 0 h) and the initial pH of PLM (pH = 6.52 at 0 h) to pH 5.48 and pH 5.72, respectively. The lower pH microenvironment resulted by the production of organic acids. The microbial conversion of complex polysaccharides to monosaccharides involves various biochemical pathways and leads to the formation of fermentative end products as short-chain fatty acids (SCFAs), lactate and ethanol [53]. The major end products of the fermentation of PWPs and PLM were lactate, acetate and ethanol in different ratio. The expected easier fermentation of the low molecular weight fractions (PLM) compared to the native water-extractable polysaccharide from _P. major_ leaves (PWPs) was proven. The major product from glucose fermentation was lactic acid while a heterofermentative process with a significant production of acetate was observed in PWPs and PLM fermentations. The lactate/acetate ratio ranged from 1:1 to 1:5 as the highest amount of acetate was observed in _L. plantarum_ S30. The l/p-lactic acid ratio varied from 1:1 to 2:1 in different strains. In agreement with our result, lactate and to a lower extent acetate, were the main end products of _L. plantarum_ fermentation using glucose and FOS under anaerobic conditions [54]. Whereas, using _Amorphorphallus konjac_ glucomannans and their hydrolyses as substrates, other authors [55; 56] found that acetic acid was the chief SCFA produced by _L. plantarum_ in in vitro fermentation. The utilization of the heterogenic PWPs and PLM by _Lactobacillus_ strains could be due to their heterofermatative pattern [57], whereas the observed strain-specificity might be result from the metabolism-specificity of the different monosaccharide units composing the structure of PWPs and PLM [53]. A Three-Way ANOVA test was performed three times in order to evaluate statistically the obtained results for the production of total lactic acid, acetic acid and ethanol by the three tested bacterial strains. In each of these three tests the independent variables (individual factors) were the same-carbon sources (glucose, PWPs and PLM), bacterial strains (_L.A._N, _L.P_ S30, _L.S._ S16 and _L.B._ S27) and time points (0 h, 6 h and 20 h). The three ANOVA tests differed in terms of the dependent variable (response)-total lactic acid, acetic acid and ethanol, respectively. The results showed that there was a statistically significant difference between the individual factors and their combination interactions for each of the three fermentation products (\(p<0.05\)). The coefficient of determination R\({}^{2}\) (0.984-0.999) indicated a considerable linear relationship between the factors and the dependant variables. Moreover, [PERSON]'s HSD tests for post-hoc analysis were carried out in each of the three different ANOVA tests, which confirmed that in the different time points (0 h, 6 h, 20 h) all the mean differences of the dependent variables were significant (Supplementary Materials: Table S2). Most of the _Lactobacillus_ and _Bifidobacterium_ strains possess large number of genes that encode carbohydrate active enzymes and can switch readily between different energy sources in the gut depending on availability. The variety of secreted enzymes allows a degradation of complex carbohydrate substrates [58; 59].