A new method of optical detection of yeast acidification power

Abstract

We describe here a newly developed method for a contact-free optical pH measurement in yeast suspensions supplemented with glucose, and containing the pH sensitive triphenylmethane dye bromocresol green. It is suitable for performing the acidification power test (based on measuring the rate of pH drop of yeast suspension caused by active extrusion of acidity from cells after glucose addition) used for assessing yeast vitality in fermentation industries. Using this methodology we monitored the pH in yeast suspensions in the course of acidification in the pH range of 3.5-5.3. Optical pH measurement allows simultaneous testing of several samples, minimizes the sample volume, simplifies sample handling and reduces the hands-on time in sample processing.

Visual and simple determination of glucose-induced acidification by yeast cells: application to rapid cytotoxicity test

“…Though bromocresol green was used as pH indicator for acidification power test in the pH range from 3.5 to 5.3 (Gabriel et al, 2008b), methyl red was used in order to detect the lower proton release at pH range from 5 to 6 in this study.…”

“…Glucose-induced acidification was found to depend on plasma membrane H þ -ATPase which plays an important role in proton efflux from yeast cells (Na et al, 1993;Viegas et al, 1995;Ambesi et al, 2000;Lecchi et al, 2005), while the dissociation of hydrated carbon dioxide and the release of organic acid were also reported to contribute to acidification in high density yeast cell suspension (Sigler and Hoffer, 1991;Myers et al, 2005). The measuring method of glucose-induced acidification with pH meter was improved to evaluate the yeast vitality in brewing practice (Sigler et al, 2006;Gabriel et al, 2008a), and the colorimetric methods also has been proposed (Pascual and Kotyk, 1982;Gabriel et al, 2008b).…”