"Yeasts Are Inexhaustible Source of Polymers, Bioactive Substances," Microbiologist Tells BTA

"Yeasts are an inexhaustible source of polymers and biologically active substances. Ecologically speaking, they are a renewable source, not a pollutant: we can extract them in large quantities without generating any waste," Assist. Prof. Dr Snezhana Rusinova of the Laboratory of Applied Biotechnologies at the Stephan Angeloff Institute of Microbiology with the Bulgarian Academy of Sciences said in a BTA interview.

The microbiologist and biotechnologist participates in the 31st Bulgarian Antarctic Expedition. Her project, titled "Biotechnological approach to obtaining biologically active molecules from Antarctic yeasts," is intended to track the biodiversity of Antarctic yeasts and explore their potential to synthesize biologically active molecules with possible pharmaceutical applications.

"Antarctic yeasts have hardly been studied from a biotechnological point of view, but in terms of biodiversity they have been studied for at least 20 years. There is a large biodiversity of yeasts throughout Antarctica both on the mainland and throughout the island archipelagos, but their potential products and use have not been explored," Dr Rusinova explained.

"The team of my research supervisor, Assoc. Prof. Pavlova, was one of the first teams to focus on cosmetic applications. Many years ago she started building Bulgaria's first and only Antarctic collection. Now I am steadily developing and enriching this collection, adding different strains brought back from Bulgarian expeditions to Antarctica," the microbiologist said.

"What we target is not just identifying the species that we have found but also exploring their ability to synthesize various antioxidants: carnoids, ergosterol, coenzyme Q10, and other bioactive substances. We have isolated other molecules so far, but we are still specifying their action," she added.

"We are also looking at the application of the extracellular products that yeasts synthesize. Early on, we were looking at cosmetic possibilities and the application of Antarctic yeast exopolysaccharide in creams, lotions and various other cosmetic products, using the polymer itself as an emulsifier and moisture-retaining agent. All these actions can be incorporated into cosmetic formulations and form part of such emulsions, i.e. polymers can be stabilizers of water-in-oil emulsions such as creams and lotions. This is very useful, as we can replace synthetic emulsifiers by those of natural origin. We are trying to find other applications, too, replacing synthetic ingredients by ingredients of natural origin.

"There are a lot of rocks on Livingston Island, but we look for places with well-formed soil, so we can take a soil sample from an approximate depth of 10 centimetres. When we take samples, we don't know for sure if they contain any yeast. Most samples show that they do. Whether we find yeast is a matter of both luck and a properly selected sampling location. We believe that more yeasts could be found around moss and grass root systems, as previous analyses of soil samples with yeasts have always found the roots of similar plants as well," said Dr Rusinova.

"If yeasts are detected when samples from the relevant habitats are isolated in laboratory conditions, we select them according to their appearance and morphological features. We can make litres out of a cell because we can culture the yeasts, first in a test tube, then in a flask, then in a laboratory bioreactor with a volume of up to 5 litres, and then eventually in an industrial bioreactor. Just a single cell must be propagated because this means that the culture is pure. We only work with pure cultures so as not to compromise the results," said the microbiologist.

"Laboratory work back in Bulgaria is much more extensive than field sampling on Livingston Island: obtaining a final product from a sample can take years," she explained.

"We have described and published the more valuable yeast strains and their properties in global research journals. Our latest publication is about the discovery of a brand new extracellular polymer of a relatively new yeast strain which has been described only once in the world so far," Dr Rusinova noted.

She hopes that the yeast samples taken from Livingstone Island will yield good results in terms of morphological diversity. If this is the case, the more productive Antarctic yeasts will be selected for culturing under different conditions to find out which ones will build up more biomass for biotechnological use.