K. Thomson (1), J. P. CARVELL (1); (1) Aber Instruments, Aberystwyth, U.K.

Poster

Determining the concentration and viability of yeast cells is critical in any brewing process where the brewer is looking for consistent product quality and the most common method of counting the number of yeast cells remains the microscope and hemacytometer. In this protocol, yeast cells are stained with methylene blue to indicate whether they are viable. The methylene blue is unable to penetrate viable cells leaving them unstained. The errors associated with the microscope protocol are high (20–30% errors are typical) due to human error, human interpretation, and low counting volume (0.1–0.2 µL). Moreover, in cases where there is background material from the brewing process, manual counting is even more challenging. Researchers need to distinguish yeast cells and non-cellular debris (hop in beer brewing, grape in wine brewing, and corn mash in bioethanol production). Many breweries are also looking to adopt cell counting and viability methods that can be carried out by skilled process operators or to automate cell counting by using on-line instrumentation such as radio-frequency impedance (RFI) spectroscopy. In order to overcome the difficulties, many automated cell-counting techniques have been developed, including digital image processing techniques with microscopic images, flow cytometry, and RFI spectroscopy. In this study, we compare a new, rapid automated yeast cell counting method using bright-field microscopic images that utilizes a disposable multi-chamber slide with traditional microscopy and live cell counts from a RFI-based instrument. We contrast the errors, ease of use, time for analysis, and costs per test for the three methods.

John Carvell is the managing director at Aber Instruments, U.K. He is a graduate in biochemistry and received his Ph.D. degree at Newcastle University, U.K., and held roles as production manager at a yeast manufacturer and senior sale roles within APV and Alfa Laval before joining Aber Instruments Ltd. With the business more than 90% export and split between both the brewing and biotechnology industries, he spends a large proportion of his time visiting key customers involved in a diverse range of applications. John has presented posters at many of the major brewing conferences and also presented papers at SIM (Society of Industrial Biotechnology), RAFT (Recent Advances in Fermentation Technology), ACS, ASBC, and IBD meetings. When time permits John enjoys a number of activities, including badminton, tennis, and fly fishing.