|Figure 1. Glass fermentation carboys. Small batch brewing methods often employ the use of glass containers for the fermentation process.|
Vienna style lager beer was produced by standard production procedures. Briefly, crushed malted barley was wetted and incubated at 77° C for approximately 60 minutes to convert grain starch to glucose by action of the endogenous α-(1→4) and α-(1→6) glycosylase enzymes present in the germinated barley. The sugar rich aqueous extract was isolated by flow through filtration and boiled for 60 minutes. Hop buds were added at intervals during the boil for flavor. After cooling, the unfermented wort was inoculated with Bavarian lager yeast (Wyeast strain 2206). The culture was sealed with an air lock and allowed to ferment at approximately 16° C. Aliquots (15 mL) were removed daily, centrifuged at 800x g and the supernatant stored at -20°C until assayed for ethanol and glucose content.
|Figure 2. Vienna style lager fermentation. Glucose is consumed by the yeast Saccharomyces cerevisiea, while ethanol is produced as a byproduct.|
During the fermentation process the production of ethanol in fermenting beer was monitored. As demonstrated in Figure 2 the ethanol concentration of fermenting Vienna lager style beer increased steadily from 0 to approximately 5.5% over a period of 350 hours (14 days). This is in good agreement with ethanol calculations based on the change in specific gravity. The initial specific gravity of the unfermented beer was determined to be 1.055 g/mL, while the final gravity was 1.010 g/mL. Using the change in gravity one can estimate the concentration of ethanol produced to be 5.9%. At the same time glucose was being consumed. Glucose is present in high concentration (approx 80 mM) in the beer at the beginning of the fermentation process and is completely consumed in the first 50 hours of fermentation (Figure 2). This rate is much faster than the production of ethanol, suggesting that glucose transporters are quickly sequestering the glucose from the media. Only as the glucose is consumed for energy by the yeast is ethanol produced.
This application is an example of making science interesting and relevant to me, in other words it was fun. What are some examples of that science projects that you would find interesting and relevant? The U.S. Department of Education’s (DOE) National Assessment of Education Progress (NAEP) report indicates that U.S. students are doing poorly in science. I will not bore you with the breakdown of the statistics, as I am sure most will agree with the overall assessment. However, if there were more opportunities where children could be exposed to science that was interesting and relevant (i.e. FUN) to them, then some of the issues with science education might be solved.
By Paul Held, Laboratory Manager