November 2020 | Resource Feature
A Green Chemistry Guided-Inquiry Lab Designing Biomimetic Songbird Preen Oil from Waste Cooking Oil
By Eleanor Byers and Anne Marteel-Parrish
Chemistry as a (Green) Creative Discipline
Chemistry is more than a subject to be learned or practiced by rote. How can we expect students to act like curious scientists, especially when they are mostly immersed in a verification laboratory setting?
Even at the high school level, I approach teaching chemistry as a creative discipline, and instill this value in my students through guided-inquiry labs where students play active roles in procedure development and data analysis. Students have greater engagement with the material when they are invested in the outcome. Guided-inquiry laboratories emphasize interpersonal skills in addition to the scientific content, which I encourage by having students consult within their group of three to four, or with another group, before asking me.
Like guided-inquiry laboratories, green chemistry also focuses on innovation and original research; students are encouraged to make choices, find alternatives, and innovate. The 12 Green Chemistry Principles, developed by Anastas and Warner, outline parameters to improve chemical products and processes in order to make them more sustainable.1 Green chemistry and its principles are finding their way into more high school classrooms, but have not become universal by any means. The earlier and more often we expose students to green chemistry, the more likely it will become second nature.
Both biomimicry (literally, the imitation of life) and the use of nature as an inspiration in new products or processes are natural partners of green chemistry. Green chemistry looks to biomimicry, as nature has found ways to function effectively even with reduced resources or changes in the environment. We humans have industrialized many processes for our own convenience and commercial development; biomimetics is about reducing this damaging pattern and increasing the sustainability of industrial processes and chemical syntheses.2 Biomimicry is an example of how students can be engaged in developing their own research methods and evaluating data. One size does not fit all — neither in guided-inquiry experiments, nor in biomimetic chemical syntheses.
Biomimetic preen oil
In this lab, students design, execute, and analyze a process aimed at synthesizing their own biomimetic product: songbird preen oil. Birds coat and protect their feathers with this waterproof and antibacterial substance, which is produced in their uropygial gland. Preen oil is composed of a wide array of organic compounds that vary by species, season, and region.3 In order to produce a biomimetic preen oil that maintains both hydrophobic and antibacterial properties, the key components of an unsaturated oil base as well as methyl ketones must be present in the final product.
Methyl ketones are responsible for the characteristic flavor and scent associated with blue cheese. Methyl ketones can be synthesized from fatty acids in milk using a mold found in blue cheese known as Penicillium roqueforti through enzymatic and oxidative processes.4,5 Inspired by the cheese-making process, I developed a process in which P. roqueforti from blue cheese slurries facilitates the reaction of fatty acids from waste cooking oil. A blue cheese slurry is composed of about 40% pre-ripened cheese solids, 55% water, and 5% salt, and must possess the characteristic flavor of the cheese.4 Fatty acids added to the slurry incubate with the P. roqueforti to produce methyl ketones.
In this lab, waste cooking oil is used as the fatty acid feedstock to apply the green chemistry principle of using renewable feedstocks. Waste cooking oil is a huge environmental pollutant, especially in developed countries, such as the United States.
|Figure 1. Waste cooking oil and blue cheese slurry.|
Designing a biomimetic preen oil synthesis
One of the main aims of the lab is to simulate a research environment for students, where they are not told what to do, and instead have the freedom to test what is most effective. From the background materials to the post-lab questions, the lab activity is presented to students in an open-ended way. Background information, experimental goals, instructions about how to design, create, and test the preen oil, as well as pre- and post-lab questions are all provided in the student handouts.
The pre-lab questions prepare students for the hands-on portion of the activity and allow them to show understanding of the principles guiding the activity, including green chemistry, biomimicry, and methyl ketones. Students use the background information provided to complete the pre-lab; additional resources are not necessary. Before the activity, students should also work with their group to outline the steps they will use when designing their biomimetic oil. In my experience, allowing students to review the background material, and even begin to write an outlined procedure before the laboratory period, is more beneficial for students than simply introducing them to the experiment and instructing them to conduct it in an allotted period of time.
Students are given an outline of the experimental goals involved in creating and mixing a slurry, and filtering and testing their oil — and then are instructed to design their own procedure in order to meet these goals. They are constrained by the materials provided, and challenged to make the procedure as environmentally friendly as possible by incorporating the principles of green chemistry. Waste cooking oil, the feedstock, is the limiting reactant. The processes and techniques used in the lab, such as slurry-making and manual filtration, may be new to high school students, but should help in improving their current level of scientific inquiry.
|Figure 2. Methylene blue test results from Day 0 (top) and Day 5 (bottom).|
During the activity, the slurry creation is the basis of the biomimetic oil design. In order to adapt a research-style experiment at the high school level, the optimal slurry ranges are provided to students as a guide. This strategy is mainly due to the time constraint as well as resource limitations. Students can choose the ratios of blue cheese, water, and salt to react with a designated volume (5 mL) of waste cooking oil to make whatever slurries they would like. If values within the given range of reactants are used, students are guaranteed to produce a successful biomimetic preen oil with methyl ketones present.
Next, the students choose a length of time for the slurry to mix and incubate with the waste cooking oil in order for the P. roqueforti to produce methyl ketones from the oil fatty acids. Finally, students filter the oil from the slurry; two distinct layers form, one made of oil and the other one water-based. The oil layer can then be filtered manually using a coffee filter. Goggles and gloves should be worn by all students for the duration of the lab; proper use of PPE should mitigate any possible allergies to reactants.
Once the biomimetic oil has been filtered, students test their product for important chemical properties such as the presence of methyl ketones, hydrophobicity, and antibacterial ability. Step-by-step procedures are given to students for the iodoform and methylene blue tests that check for the presence of methyl ketones and antibacterial properties, respectively; however, students develop their own simple test for hydrophobicity. It would be prudent for students to wear gloves in addition to their goggles during the testing process, due to the 3M NaOH and iodine chemicals used. Students complete a data sheet, meant to mimic a research notebook, as they work to create and test their biomimetic oil.
After the lab, students are not asked to verify that they achieved an expected result. Instead, they are asked to evaluate and think about how to improve their design processes in a post-lab assignment in which the questions focus on self-reflection and forward thinking.
Student response to lab
The biomimicry-focused guided-inquiry lab described above was implemented in three high schools (two public and one private) in four introductory 10th-grade chemistry classrooms. Students who completed the lab provided feedback on its effectiveness and quality. These experiments were run under Washington College Institutional Review Board for Research on Human Subjects experimental number FA19-060. Students in the private school chemistry class had worked with guided-inquiry labs in their classroom earlier in the year. None of the students in either of the two public schools had ever been exposed to a guided-inquiry chemistry lab.
I implemented the lab as supplemental instruction to expose students to the topics of green chemistry and biomimicry, topics not commonly covered in high school chemistry curricula. The lab gives them real-world practice with units and significant figures, use of laboratory equipment, and the inclusion of mathematical concepts in science by calculating percentages. If this lab were to be implemented as an integral part of the curriculum, I would incorporate it into a chemical bonding or molecular structure unit to develop the connection between chemical form and macroscale function.
Students are told that the synthesized material needs to be hydrophobic, so one question that may follow is, What type of molecules does it need to be comprised of? Also, students will quickly think of oils that repel water, so another question could be, If we need the product to exhibit antibacterial properties on a macroscale, what would that look like on a microscale? Students are provided answers to these questions through their introduction to P. roqueforti and its role in creating antibacterial methyl ketones.
When asked to identify their favorite part of the activity, students mentioned either:
- the lab experience (including the equipment, procedure, reactants, etc.),
- testing their biomimetic oil,
- being afforded independence, or
- the novel ideas/concepts behind the activity.
Students especially enjoyed the testing of the product, as they felt this was extremely applicable to a real-life situation. It was gratifying for them to have chemically created a new product, and then determine if it had the desired properties. Students reported loving the new lab pattern, having fun, feeling less stressed than during normal labs, and valuing the environmental connection.
Students were similarly united in which parts they enjoyed least, which included:
- the independence expected of them,
- the blue cheese reactant (specifically the smell, and not being used to working with something like it in chemistry class),
- their group’s time management relating to completing the experimental goals according to a schedule of their own making, or
- difficulty with various steps of the procedure.
Students who were familiar with verification labs were extremely uncomfortable with the freedom being afforded to them. They would often check in with me to make sure they were on the right track. During implementation, it was stressed to all students that there is not just one correct answer. The important pieces of the activity and biomimetic design are about the process and applying divergent thinking.
Students who had not worked in a guided-inquiry lab before also reported struggling with time management, since they were not used to such freedom and tended to want to tackle all steps at once. To remedy this, I notified the students in advance of the recommended time dedicated to each step so they could divide the tasks ahead of time. To add more structure to the in-class time for students new to guided-inquiry, I found it useful to set timers for each experimental goal. This ensured that students were progressing through the activity by being responsible for a specific task. Overall, this approach helps ensure students can complete each step without feeling rushed toward the end.
Technique-wise, during the activity, students struggled most with the gravity filtration to recover the biomimetic oil, the most manually “finicky” step of the experiment. However, this is the only type of filtration that can be universally done in high school chemistry classrooms that leads to clear, recovered biomimetic oil that is completely separated from any remaining slurry contaminants.
Even though many students were unsure at first, after reflecting on the lab, many liked the novel concept of a guided-inquiry laboratory activity integrating green chemistry and biomimicry. Most were also positively surprised how much the activity differed from their before-lab expectations: 76% of students felt the new approach was the most significant and positive difference, 17% of students appreciated the new knowledge/topic of the laboratory activity, and only 3% of students thought there was no difference from their expectations.
Why biomimicry and green chemistry through guided-inquiry?
Research-based labs that focus on guided-inquiry, when introduced and continually implemented in all types of secondary classrooms, allow students to develop valuable skills such as problem-solving, independence, resilience, and collaboration.
The real-world applications in this lab span multiple disciplines, such as environmental science, engineering processes, and of course, green chemistry. Overall, both the green chemical synthesis and preen oil biomimicry, as well as the application of these topics in high school chemistry classrooms through guided-inquiry, are effective for both student and teacher, and should be expanded upon. After completing this lab, students displayed continued interest in green chemistry and biomimicry — vital topics for them as future scientists, engineers, and citizens.
- Anastas, P. T.; Warner, J. C. Green Chemistry: Theory and Practice (Oxford University Press, New York, 1998).
- Hwang, J.; Jeong, Y.; Park, J. M., Lee; K. H.; Hong, J. W., Choi, J. Biomimetics: Forecasting the Future of Science, Engineering, and Medicine. International Journal of Nanomedicine. 2015, 10(1), 5701–5713, https://doi.org/10.2147/IJN.S83642.
- Czirják, G. A.; Pap, P. L.; Vágási, C. I.; Giraudeau, M.; Mureşan, C.; Mirleau, P.; Heeb, P. Preen Gland Removal Increases Plumage Bacterial Load but Not That of Feather-Degrading Bacteria. Naturwissenschaften, 2013, 100, no. 2, 145–51, https://doi.org/10.1007/s00114-012-1005-2.
- Microbiology and Biochemistry of Cheese and Fermented Milk, Second Edition; Law, B. A., ed.; Springer: Berkshire, UK, 2013.
- King, R. D.; Clegg, G. H. The metabolism of fatty acids, methyl ketones and secondary alcohols by penicillium roqueforti in blue cheese slurries. Journal of the Science of Food and Agriculture. 1979, 30, No. 2 (February), 197–202. https://doi.org/10.1002/jsfa.2740300215.
(article cover) Peampath/Bigstockphoto.comm