Selection of yeast strains for ethanol production based on grain substrates
Students Name: Voitetska Mariia
Qualification Level: magister
Speciality: Biotechnology and Bioengineering
Institute: Institute of Chemistry and Chemical Technologies
Mode of Study: full
Academic Year: 2024-2025 н.р.
Language of Defence: ukrainian
Abstract: Voitetska M. Yu.; Khomiak S. V. (supervisor). "Selection of yeast strains for ethanol production based on grain substrates." Master’s Qualification Thesis. – Lviv Polytechnic National University. Lviv, 2024. Extended abstract Study object - Saccharomyces cerevisiae yeast strains. Scope of research: yeast strain selection and optimization of fermentation conditions. Goal of Research: To isolate and identify a yeast strain from natural sources capable of efficiently fermenting grain-based substrates for bioethanol production, thereby contributing to the country’s demand for bioethanol fuel. This master’s thesis examines the selection of yeast strains for efficient bioethanol production from grain-based substrates, aimed at developing a sustainable biofuel solution to meet national energy demand. The research utilizes a technological process that involves fermenting hydrolyzed grain substrates with Saccharomyces cerevisiae yeast cells, followed by rectification to purify the final product. The findings have practical implications for the design of bioethanol production facilities using agricultural byproducts, which can help address energy needs while mitigating environmental and economic issues. A key focus of this research is the optimization of yeast strains specifically adapted to ferment grain substrates, with the objective of maximizing bioethanol yield. The study incorporates innovative approaches, including the testing of both natural and commercial yeast strains, and evaluates their performance under various temperature regimes and fermentation conditions. Special attention is given to substrate pretreatment as a critical factor for process optimization. In the experimental section of the study, selected yeast strains were evaluated based on their fermentation rate of corn substrates over 11 days, and ethanol yield was determined for each strain. Ethanol samples were analyzed using IR spectrophotometry to assess water and ethanol content, which helped identify the most effective strains. Fermentation was conducted at temperatures ranging from 30°C to 37°C, allowing the selection of the most efficient strain, RC, which demonstrated the highest activity and fermented the largest amount of mash. Although strain DC showed the highest alcohol yield at 30°C, it was later outperformed by strain RC at other tested temperatures. The study also presents a technological scheme for bioethanol production, providing a practical framework for industrial application. The conclusions formulated in this thesis align with existing literature and are based on experimental data obtained using modern physicochemical and microbiological research methods, including IR spectrophotometry and selective breeding techniques. Key words: Bioethanol production, yeast strain selection, corn, Saccharomyces cerevisiae, grain-based substrates, fermentation, hydrolysis, biofuel, IR spectrophotometry, renewable energy. References: 1. Bhaskar T, Bhavya B, Singh R, Naik DV, Kumar A, Goyal HB. Thermochemical conversion of biomass to biofuels. In: Pandey A, Larroche C, Ricke SC, Dussap CG, Gnansounou E, editors. Biofuels – Alternative feedstocks an conversion processes. Oxford, UK: Academic Press; 2011. pp. 51–77 https://doi.org/10.1016/B978-0-12-385099-7.00003-6. 2. Lange J. Lignocellulose conversion: An introduction to chemistry, process and economics. Biofuels Bioprod Biorefin. 2007;1(1):39-48, https://doi.org/10.1002/bbb.7 3. Mussatto S, Dragone G, Guimaraes P, Silva J, Carneiro L, Roberto I. Technological trends, global market, and challenges of bio-ethanol production. Biotechnol Adv. 2010;28(6):817-30, https://doi.org/10.1016/j.biotechadv.2010.07.001. 4. Jobling S. Improving starch for food and industrial applications. Curr Opin Plant Biol. 2004;7(2):210-8, https://doi.org/10.1016/j.pbi.2003.12.001. 5. Shigechi H, Koh J, Fujita Y, Matsumoto T, Bito Y, Ueda M. Direct production of ethanol from raw corn starch via fermentation by use of a novel surface-engineered yeast strain codisplaying glucoamylase and ?-amylase. Appl Environ Microbiol. 2004;70(8):5037-40, https://doi.org/10.1128/AEM.70.8.5037-5040.2004