Yogyakarta, July 21, 2025 — The Doctoral Program in Biotechnology, Graduate School of Universitas Gadjah Mada, held a closed doctoral examination for Medhina Magdalena (cohort 2018) on Monday, July 21, 2025. The examination was chaired by the Dean of the Graduate School, Universitas Gadjah Mada.
Medhina defended her dissertation entitled:
“Studi Potensi Keragaman Khamir dari Madu Hutan dan Buah-Buahan serta Pemanfaatannya pada Fermentasi Etanol”
(“Diversity of Yeasts from Forest Honey and Fruits and Their Application in Ethanol Fermentation”)
Her research explored the biodiversity of yeasts from forest honey and tropical fruits collected from various Indonesian islands, including Sumatra, Java, Kalimantan, Sulawesi, and Nusa Tenggara. The study aimed to discover new Saccharomyces cerevisiae strains capable of improving ethanol fermentation efficiency, particularly by reducing the accumulation of residual fructose—an issue that often leads to incomplete fermentation and reduced ethanol yields.
Through a series of screenings, molecular identifications, and fermentation trials, Medhina identified four promising S. cerevisiae strains from fruits such as grapes and pineapple. Among them, strains NB1 and Ag3 showed superior performance in lowering residual sugars and generating higher ethanol concentrations when fermenting mixed sugar substrates. Gene expression analysis revealed that the hexose transporter Hxt3 maintained relatively high expression throughout the fermentation process, suggesting its key role in sugar transport and utilization under stress conditions. Although the presence of the Fsy1 fructose symporter was functionally suspected, its gene was not amplified in the tested isolates, indicating the need for further investigation into alternative sugar transport mechanisms.
This research demonstrates the importance of indigenous microbial resources in supporting green and sustainable energy production through bioethanol. It also enriches scientific understanding of tropical yeast diversity and its biotechnological applications.
As part of her doctoral accomplishments, Medhina has published a peer-reviewed article titled “Yeast Diversity in Honey Produced by Wild Honeybees at Different Elevations” in the Baghdad Science Journal (Scopus Q2). This publication contributes to the global documentation of microbial diversity in forest ecosystems.
Medhina was supervised by Prof. Donny Widianto, Ph.D and Prof. Irfan D. Prijambada, Ph.D. The examination committee included Prof. Dr. Yekti Asih Purwestri, Prof. Dr. Endah Retnaningrum, Prof. Triwibowo Yuwono, Ph.D, and Dr. Ahmad Fathoni, M.Eng from the National Research and Innovation Agency (BRIN).
The outcomes of this dissertation strongly align with several Sustainable Development Goals (SDGs): SDG 7 (Affordable and Clean Energy) through the advancement of renewable bioethanol sources, SDG 12 (Responsible Consumption and Production) by promoting the sustainable use of untapped microbial biodiversity, and SDG 15 (Life on Land) through the conservation and purposeful application of native microbial ecosystems in tropical forest environments.