by: Sheena Gaudia (Chromoplexy)
Yeasts are eukaryotic, single-celled microorganisms classified under the Kingdom Fungi, and they are found in various places such as soil, water, and surfaces. They are typically used in the food industry, particularly in the production of bread, beer, and wine, since yeasts are used to cause fermentation and leavening. Apart from these, yeasts are also utilized to produce medicine and biofuels aside from food production.
The Rhodotorula species are known for their ability to cause infections, but the research revealed that Rhodotorula species also have a biofuel source potential. The Rhodotorula species are known for their pigmented colonies that range from pink, coral, and red due to the presence of carotenoids, giving them the unique characteristic orange or red color. They are also highly tolerant to extreme conditions, making them a good source of microbial oils due to their lipid-accumulating characteristics.
Biodiesel is a renewable and biodegradable fuel made from vegetable oils, animal fats, or even recycled restaurant grease. Oleaginous yeast is a strong candidate for a potential biofuel source for its capacity to store more than 20% of its cell dry weight as lipids (Lopez et al., 2022). People are leaning towards future adoption of biofuels due to their high potential to reduce emissions and decrease dependency on fossil fuels. Additionally, they offer a renewable and more environmentally friendly energy source.
A recent local study explored the potential of yeasts from the Mount Makiling Forest Reserve, specifically the Rhodotorula genus. The study followed a systematic approach of using yeast isolation. Lipid extraction and analysis were performed to determine the quantity and kind of oil that was produced. DNA analysis was then conducted to determine the genes involved in fat production using the yeast’s entire genetic code.
Results showed that a total of 258 colonies appeared to be yeasts isolated from epiphytic ferns, moss, roots, orchids, and several other trees in Makiling Forest. The study utilized typical fat staining techniques using Sudan Black B, Sudan III, or Nile red staining to serve as a qualitative screening tool in selecting potential oleaginous yeasts isolated from different sources. For biomass and lipid production, it was revealed that NFR6 and BUB8 accumulated the most mass and lipid content, with BUB8 having the more significant biomass and having de novo and ex novo lipid accumulation. This suggests that the isolated strain can use different materials such as agricultural wastes and industrial origins.
The lipid content among oleaginous yeasts is commonly acknowledged to be the same as vegetable oils that contain myristic (C14:0), palmitic (C16:0), palmitoleic (C16:1), stearic (C18:0), oleic (C18:1), linoleic (C18:2), and α-linolenic acid (C18:3). The fatty acid profile of BUB8 showed that oleic acid was the most abundant, followed by palmitic acid, linoleic acid, and stearic acid. The identification of fatty acid composition is a notable determinant of the biofuel’s quality. Whereas high levels of monounsaturated fatty acids are preferred for a biodiesel substrate. It was also revealed among studies that biodiesel production from oleic acid is the ideal diesel substitute; hence, BUB8 is considered to be a good candidate for biodiesel production.
Given its notable and high potential for future use, there are still multiple variables that need to be considered. Laboratory conditions are highly controlled, but doing industrial-scale experiments may present challenges such as their costs to maintain and their consistency. While this is a promising study, there is still work that needs to be done, such as enhancing better oil yield among strains, economic feasibility, especially in cost production, the sustainability of the project, especially its environmental impact, and its compliance with regulatory requirements for mass-scale use.
SOURCES
Pajares, I. G., Ramos, K. R. M., Montecillo, A. D., Elegado, F. B., & Raymundo, A. K. (2024). Draft genome sequence of Rhodotorula sp. BUB8, an oleaginous yeast isolated from Mt. Makiling Forest Reserve, Laguna, Philippines. Microbiology Resource Announcements, 13(10), e0037724. https://doi.org/10.1128/mra.00377-24
Pajares, I. G., Requiso, P. J., Fabro, L. M., Jr, Ramos, K. R. M., & Raymundo, A. K. (2024). Biodiesel production of oleaginous yeast isolated from the Mount Makiling Forest Reserve. Journal of Applied Biology & Biotechnology. https://doi.org/10.7324/jabb.2024.153703
Salvador López, J. M., Vandeputte, M., & Van Bogaert, I. N. A. (2022). Oleaginous yeasts: Time to rethink the definition? Yeast (Chichester, England), 39(11–12), 553–606. https://doi.org/10.1002/yea.3827
This article was originally published in the GENEWS May 2025 Issue.
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