@article{vann_layfield_sheppard_2017, title={The application of near-infrared spectroscopy in beer fermentation for online monitoring of critical process parameters and their integration into a novel feedforward control strategy}, volume={123}, ISSN={["2050-0416"]}, DOI={10.1002/jib.440}, abstractNote={Traditional methods used in the analysis of fermentation media suffer from a number of limitations. The search for more rapid and efficient methods has led to the development and application of near-infrared spectroscopy. Near-infrared spectroscopy has been applied successfully in a variety of industrial processes: agricultural, food, chemical and pharmaceutical, generally in the areas of raw material quality control but also including intermediate and finished product testing. The present research explores its potential for online fermentation monitoring of total cell count (TCC), specific gravity (SG), free amino nitrogen (FAN) and percentage alcohol by volume (% v v−1) in a 300 L pilot-scale validation batch. Models that were generated from three calibration batches for each of these constituents exhibited overall favourable standard error of cross validation (SECV) and fit of predicted vs actual cross validated results (SECV, R2): SG (0.00072, 0.995), ethanol (0.17% v v−1, 0.990), FAN (16.5 mg L−1, 0.886) and TCC (1.24 × 106 cells mL−1, 0.640). The data that was most relevant to cell metabolism was determined to be sugar consumption rate, ethanol production rate, yield of ethanol and fermentation lag time. These ‘critical performance parameters’ were incorporated into a novel feed-forward control strategy where yeast pitching rate was modified based on values of the critical performance parameters from the previous batch. Use of this feed-forward strategy demonstrated how brewers can utilize near-infrared monitoring for quality assurance through early detection of shifts in fermentation performance. Copyright © 2017 The Institute of Brewing & Distilling}, number={3}, journal={JOURNAL OF THE INSTITUTE OF BREWING}, author={Vann, Lucas and Layfield, Johnathon B. and Sheppard, John D.}, year={2017}, month={Jul}, pages={347–360} }
 @article{layfield_vann_sheppard_2014, title={A Novel Method of Inducing and Retaining Cell Cycle Synchronization in Cultures of Saccharomyces cerevisiae}, volume={72}, ISSN={["1943-7854"]}, DOI={10.1094/asbcj-2014-0324-02}, abstractNote={In conventional fermentation, at any one time, individual yeast cells are randomly distributed with respect to the stage of their growth and division cycle. The observed metabolic performance is, therefore, the result of an average of the entire population. In contrast, a synchronous population is characterized by cells that are aligned with respect to their metabolic processes, traversing the cell cycle and dividing mostly in unison. In this study, a novel method for inducing and retaining cell cycle synchronization in yeast cultures (diploid and polyploid-type) was developed using a simple and natural phased expansion method, in which the volume of the culture was increased step-wise at time periods equal to the cell doubling time. Results indicate that this method was effective in producing yeast cultures with a high degree of synchrony, verified by cell counts and fluorescent cytometry. When stored in relatively small volumes at −80°C in glycerol, the cultures maintained their synchrony upon thawing. Experiments were also conducted at the lab-scale to assess the potential use of synchronous cultures in brewing applications. The incorporation of phased seed expansion and periodic feeding of the yeast culture provided increased metabolic uniformity within the population and reduced variability in fermentation performance.}, number={2}, journal={JOURNAL OF THE AMERICAN SOCIETY OF BREWING CHEMISTS}, author={Layfield, J. Blake and Vann, Lucas R. and Sheppard, John D.}, year={2014}, pages={102–109} }