The potential of bioethanol production in marine yeasts and investigation of the optimal conditions of production in the selected isolates

Factors such as energy consumption, population growth, and anticipated increases in fuel prices are driving the world towards transitioning to cleaner sources of energy. One promising alternative is the production of bioethanol from marine microorganisms, which is gaining attention due to its economic viability and minimal environmental impact. The objective of this study was to isolate and identify yeast strains from the water and sediments of the Bushehr coast that have the ability to produce bioethanol. Furthermore, the study aimed to determine the optimal production conditions for the most effective strain. 18 yeast strains were isolated and identified using morphological and molecular methods. The results of the molecular analyses showed that the isolated yeasts belonged to the genera Pichia and Candida . After assessing the amount of CO ₂ produced during the fermentation process, the following strains were selected as the top bioethanol producers: Pichia sp. isolate BK10, Pichia kudriavzevii isolate BK40, Pichia kudriavzevii isolate BK50, Pichia fermentans isolate MK20, and Candida parapsilosis isolate BK30. In our study, we produced bioethanol using the microfermentation method and experimented with different carbon sources like glucose, fructose, lactose, and sucrose. We found that the highest alcohol yield of 12.73% was achieved when glucose was used as the carbon source. Additionally, when we induced mutations with UV-30W light in the superior strain, bioethanol production increased to 15.2%. These marine yeasts have great potential for industrial use in the future, and they could potentially cover alcohol production at the level of small bioreactors.