## 4 Discussion  
In response to contemporary and future challenges for the food production sector in achieving sustainable development goals, the work presents an innovative solution for managing problematic food waste, such as bakery waste. It is also in line with current trends concerning the development of non-dairy fermented products including fermented beverages, which is associated with the increase in various health problems such as lactose intolerance. Applying lactic acid fermentation to cereal raw materials may be problematic due to the fact that LAB does not have good properties in converting starch into lactic acid, although some strains, including _L. plantarum_, show such activity [46]. However, the beneficial properties of LAB make them an attractive subject of research for new fermented products. It is worth emphasizing that bakery waste is rarely used as a matrix for composing a fermented beverage, so literature data in this area are strongly limited. [PERSON] et al. [47] used wheat bran, a major by-product of wheat processing, containing different nutritional constituents, such as proteins, carbohydrates, vitamins, and minerals, together with red beetroot/carrots to prepare fermented beverages. As the starter culture, two strains of _L. plantarum_ (BR9 and P3) and _L. acidophilus_ IBB801 were used. Similar to the results obtained in our work, in the final product the pH was, in most cases, below 3.5 and spoilage microbiota such as enterobacteria were not detected. [PERSON] et al. [48] described beverages based on flour from bread waste fermented using commercial starters Nu-trish(r) LGG(r) and Nu-trish(r) BY-01 DA. Regarding the number of LAB and _Bifidobacterium_ in beverages after 24 h of fermentation, the authors recorded values similar to the present study. Beverages fermented with Nu-trish(r) LGG(r) starter reached bacterial levels above \(10^{8}\) CFU/g, while beverages fermented with the Nu-trish(r) BY-01 DA saturator acquired lower values of \(10^{3}\)-\(10^{7}\) CFU/g, depending on the prepared variant. Moreover, [PERSON] et al. [48] found that the content of organic acids in the tested beverages ensures the pH value of the beverages, allowing the microbiological stability of the product to be maintained. Lactic acid fermentation of bread slurries using the _L. rhamnus_ GG ATCC 53103 strain was also carried out by [PERSON] et al. [49]. In the prepared fermented bread slurries (2.5% \(w\)/\(w\), dry weight) after 16 h of fermentation, the authors recorded _L. rhamnus_ at a concentration of 7.7 log CFU/g and a pH close to 3.5. The authors obtained a higher number of _L. rhamnus_, above \(10^{8}\) CFU/g, with an increased share of bread slurry (to 5% \(w\)/\(w\), dry weight) after 16 and 24 h of fermentation. While the pH value of the fermented bread slurries prepared by [PERSON] et al. [49] was close to the pH of the BWBs tested in this study (after 24 h fermentation), the LAB number obtained by [PERSON] et al. [49] was lower. Determining the antimicrobial activity of the fermented beverages was crucial due to their potential health-promoting properties; however, the presented data also indicate that the activity of fermented BWBs depended mostly on the genus of indicator bacteria, as well as on the concentration of the beverages. The higher degree of growth inhibition of indicator microorganisms was also observed with the extension of the fermentation time. In most cases, the addition of ground flaxseed to beverages had a positive effect on increasing the antimicrobial activity of BWBs. The antibacterial properties of fermented drinks are rarely an evaluation criterion. Very few data apply to products made from waste. Typically, antimicrobial properties are determined for strains subsequently used to produce the beverages. Nevertheless, some authors have also evaluated these properties. Similar to our results, [PERSON] et al. [47] observed inhibition of _Listeria monocytogenes_, _Salmonella enterica_, _Staphylococcus aureus_, and _E.