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.
