June 26, 2011
June 26, 2011
June 29, 2011
22.1623.1 - 22.1623.13
Using Kefir to teach microbial kinetics in an undergraduate wastewater treatment courseReaction kinetics is often taught at the beginning of undergraduate environmental engineeringcourses in order to help students understand temporal relationships in processes such as drinkingwater disinfection, secondary treatment of wastewater, and remediation of contaminated soil.Although some students intuitively understand concepts without physical examples, otherstudents find reaction kinetics abstract and difficult to grasp in the absence of firsthandobservation or kinesthetic manipulation of the variables that influence reaction rate. Traditionallyit has been challenging to give students learning activities that enable them to observe andmanipulate biological systems, particularly in the case of wastewater treatment; it is difficult inan undergraduate academic environment to work with pathogenic microorganisms derived fromwastewater samples due to concerns over student infection, the inconvenience associated withproviding substrate (i.e., wastewater), and difficulties associated with providing students withunrestrained lab access in order to take frequent measurements and make adjustments to growingconditions. Thus, it is clear that an alternative eliminating these challenges would be anadvancement towards giving students the opportunity to have hands-on experience withbiological growth, and better understand the factors that influence reaction kinetics.Kefir is a drink that originates from the Caucus region of Eurasia, and is similar in appearanceand taste to unsweetened drinkable yogurt. The production of kefir depends on the presence ofkefir grains, which are colonies of bacteria and yeast that live in a jelly-like cluster that is placedinto milk during kefir production. The growth of kefir, wherein microorganisms consume asubstrate (milk), generate a by-product (kefir), and increase in cellular mass, has analogues tosuspended growth secondary treatment of wastewater. Like the reduction of biochemical oxygendemand (BOD) by bacteria in secondary treatment aeration basins, kefir production is affectedby factors such as temperature, concentration of dissolved oxygen (DO), food-to-microorganism(F:M) ratio, pH, mixing, and the presence of inhibitory substances such as inorganic and organiccontaminants. However, since the bacteria and yeasts in kefir are not pathogenic, it is possiblefor undergraduate students to handle and manipulate samples with no concerns about becomingsick, and since the substrate required for kefir growth is milk, the unpleasant handling ofwastewater samples is avoided.Undergraduate engineering students enrolled in a wastewater treatment course were assigned tocharacterize the kinetics of kefir production, including the effects of change in temperature, DO,F:M ratio, and other factors. Student teams were supplied with kefir grains, and wereresponsible for the ongoing growth and survival of kefir colonies. During experimentationstudents changed growth conditions in order to observe the effect on kefir production rate, andmeasured a variety of indicators of process performance. Students fit data to kinetic models, andderived growth constants that were then used in the design of a hypothetical scaled kefirproduction process. Feedback gathered from students indicated enthusiasm with the project andenhanced understanding of reaction kinetics. Gaining independent, self-directed experience inthe lab provided students with an important preview of what it might be like in a graduateresearch environment.
Wait, I. W., & McCormick, R. F., & Wait, S. M. (2011, June), Using Kefir to Teach Microbial Kinetics in an Undergraduate Wastewater Treatment Course Paper presented at 2011 ASEE Annual Conference & Exposition, Vancouver, BC. https://peer.asee.org/18672
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