New Yeast-Based COVID-19 Diagnostic Test Could Detect SARS-CoV-2 in Saliva Faster Than RT-PCR

The yeast-based COVID-19 diagnostic test being developed by BIOinFOOD (São Paulo, Brazil) uses a biosensor consisting of a genetically modified brewer's yeast (Saccharomyces cerevisiae), which changes color if human ACE2 receptor expressed by the yeast's membrane binds to the spike glycoprotein present on the external surface of the virus.

The innovation involved in the COVID-19 diagnostic test came out of a technology mastered previously by BIOinFOOD. The firm offers a biotech platform based on S. cerevisiae, a versatile microorganism widely used in industry as a biofactory. Organic acids, amino acids, enzymes, and therapeutic proteins are some of the outputs of the platform. The firm also develops custom yeasts for use by bakeries and breweries to suit consumer tastes.

According to the researchers' expectations, the new test will be both fast and cheaper than RT-PCR because of the low cost of yeast, the main input. Another important difference is that it will probably use saliva. Being non-invasive is an advantage for diagnostic tests. Many people experience intense discomfort when undergoing collection of their material by nasal swab. Additionally, the sensitivity of the test is expected to be high, meaning it will be able to detect the virus only a few days after infection. Once the working hypothesis has been fully validated, the scientists expect the test to be brought to market and freely available for purchase during first-half 2021. The raw materials for the product are simple and distribution of the diagnostic test should be logistically straightforward.

"The yeast is normally beige. When this interaction takes place, the presence of the virus is signaled by a fluorescent green that can easily be detected by the equipment typically found in clinical analysis labs," said Gleidson Silva Teixeira, one of BIOinFOOD's partners. "We plan eventually to have the yeast emit red light, which will be easier to identify. In this case, anyone will be perfectly capable of using the test, even at home."

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