usingmethods 2 and 3, it should be pointed out that the use of an alkalinesolution for neutralization could cause a structural change of com-pounds. Consequently, the interpretation of their biological effectcan be misleading. Exemplarily, the neutralization of the acidic sep-aration of catechins in green tea by an alkali treatment (method3) caused the loss of the bio-response although the backgroundcolor was violet (Fig. 3f). Thus, a buffer solution at a biologicalpH range was preferred and tested next. The forth plate sectionwas immersed in a citric acid-phosphate buffer (0.02 M) at pH 7.8(method 4). Nevertheless, the bioassay was not successful (Fig. S-6c). The pH value of this plate was measured to be 5, which wasequivalent to the pH of the developed plate. The buffer capacity wasnot sufficient to compensate for the residual acid traces. A neutralpH value of the plate (7.0 ± 0.2), which was ideal for the viability ofthe bacteria (Fig. 3d and e), was first achieved by immersion of theplate into a 10-fold increased buffer concentration (0.2 M, pH 7.8,method 5).To conclude, the pH value of the developed plate used for DB,played a substantial role in the success or failure of the bioau-tographic workflow. The plate pH has to match the appropriatepH value of the microorganisms. Thus, it is inconceivable that thisplate pH influence on the B. s. bioassay has not been discussed inliterature so far.3.5.