Lucas Vann (1), John Sheppard (1); (1) North Carolina State University, Raleigh, NC, U.S.A.

Yeast, Fermentation, and Microbiology

A goal of paramount importance to any industrial process is the ability to consistently produce a product of the same quality batch after batch. This especially holds true in the food and biotechnological industries, such as brewing, where microbial cells are used to convert raw materials into product. As with any biotechnological process, one of the major challenges that brewers face is the ability to produce beer with a consistent flavor profile, especially within the craft industry. The causes of this variability can be divided into two broad categories: environmental and microbiological. Product inconsistency due to variable yeast metabolism routinely occurs and is directly related to the handling and management of the culture. Improper culture management is magnified in industrial beer fermentations due to the fact that a portion of the yeast from the previous batch is used to initiate the subsequent batch in what is referred to as cropping and repitching. Any successful strategy must, therefore, take into consideration the physiological state of the culture, the concentration of the yeast being repitched and the environmental conditions. As such, it is desirable to be able to monitor and control critical parameters during fermentation, as well as incorporate a feed-forward control strategy to optimize repitching. The present research explores the potential for on-line fermentation monitoring and control using near infrared spectroscopy (NIRs) of specific gravity (SG), free amino nitrogen (FAN) and percent alcohol by volume (% ABV) and the subsequent determination of repitching rate in a feed-forward control strategy based on those parameters. The findings support the possibility of incorporating NIRs into commercial brewing operations to optimize repitching strategies for better yeast management, with the goal of providing more consistent fermentation performance from batch to batch.

Lucas Vann is a senior scientist in the Biomanufacturing Training and Education Center at North Carolina State University. He develops and teaches courses to NC State students, industry professionals and FDA inspectors related to upstream biomanufacturing for the production of biopharmaceuticals and has extensive experience in the areas of fermentation, cell culture, process development and automation. He has over 10 years of upstream bioprocessing experience and is involved in industry-related bioprocess development projects at BTEC, where he provides strategic technical direction and guidance. He is currently pursuing a doctoral degree in bioprocessing at North Carolina State University, where he is conducting research specializing in bioprocess development and automation for process optimization. He holds both bachelor’s and master’s degrees in biosystems engineering from McGill University, where he helped design and develop a biosensor for fermentation process control.