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Exploring Catalase and Invertase Activity Using Sodium Alginate-Encapsulated Yeast (Yeast Spheres)†

Finding the right enzyme experiment can be problematic, depending what one is trying to show, what supplies and equipment are available, and the time one can devote to the topic. I’ve developed simple and inexpensive labs for looking at catalase and invertase activity using yeast encapsulated in sodium alginate. Single-celled yeast, Saccharomyces cerevisiae, are encapsulated in sodium alginate, a readily available extract from brown algae that, when it comes in contact with calcium chloride (CaCl2), forms a sphere or “bead.” These spheres may then be put into a solution containing substrate to test for enzyme activity. The spheres are easy to manipulate, one doesn’t have the variability and mess of a yeast solution, and since there are no cells in solution, there is nothing to interfere with the various assay methods one might want to use to test for product. The graduated cylinder method for testing catalase activity introduced here is especially good for collecting large amounts of data that enable students to use statistics and, unlike similar yeast catalase experiments using paper disks and a yeast solution, the yeast spheres are easy to manipulate and there is very little variability. I have used this procedure with students in class and with teachers in workshops with positive results and comments.