Microcystin-detoxifying recombinant Saccharomyces cerevisiae expressing the mlrA gene from Sphingosinicella microcystinivorans B9

Authors: DE GODOI SILVA, FERNANDO - State University Of Londrina; DIAS LOPES, DAIANE - State University Of Londrina; Hector, Ronald - Ron; DO NASCIMENTO, MAIKON THIAGO - State University Of Londrina; DE AVILA MIGUEL, TATIANA - State University Of Londrina; KURODA, EMÍLIA KIYOMI - State University Of Londrina; ANDRADE DE NOBREAG, GISELE MARIA - State University Of Londrina; HARADA, KEN-ICHI - Meijo University; HIROOKA, ELISA YOKO - Meijo University

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2023
Publication Date: 2/24/2023
Citation: de Godoi Silva, F., Dias Lopes, D., Hector, R.E., do Nascimento, M., de Avila Miguel, T., Kuroda, E., Andrade de Nobreag, G., Harada, K., Hirooka, E. 2023. Microcystin-detoxifying recombinant Saccharomyces cerevisiae expressing the mlrA gene from Sphingosinicella microcystinivorans B9. Microorganisms. 11(3). Article 575. https://doi.org/10.3390/microorganisms11030575.
DOI: https://doi.org/10.3390/microorganisms11030575

Interpretive Summary: Harmful blooms of cyanobacteria in water are a global problem. The toxins produced by the cyanobacteria are called microcystins and are harmful to humans, fish, and birds.They also lead to large economic losses (~$80 million) for seafood, tourism, and restaurant industries. They are also a health issue because exposure to toxins from these blooms can cause liver damage. People are exposed from eating contaminated shellfish and seafood, drinking contaminated water, or topical exposure from swimming in contaminated water. This study investigated the use of engineered brewer’s yeast (Saccharomyces cerevisiae) for expressing an enzyme that degrades the microcystin toxin, thereby reducing its concentration in contaminated water supplies. The enzyme was successfully produced by the engineered yeast and these yeast were able to reduce the toxin level by 83% under laboratory conditions. These yeast are now being investigated for removal of microcystin toxins from contaminated water. Eventual success will help to secure safer drinking water and seafood and, therefore, would directly benefit the American public.

Technical Abstract: Contamination of water by microcystins is a global problem. These potent hepatotoxins demand constant monitoring and control methods in potable water. Promising approaches to reduce contamination risks have focused on natural microcystin biodegradation led by enzymes encoded by the mlrABCD genes. The first enzyme of this system (mlrA) linearizes microcystin structure, reducing toxicity and stability. Heterologous expression of mlrA in different microorganisms may enhance its production and activity, promote additional knowledge on the enzyme, and support feasible applications. In this context, we intended to express the mlrA gene from Sphingosinicella microcystinivorans B9 in an industrial Saccharomyces cerevisiae strain as an innovative biological alternative to degrade microcystins. The mlrA gene was codon-optimized for expression in yeast, and either expressed from a plasmid or through chromosomal integration at the URA3 locus. Recombinant and wild yeasts were cultivated in medium contaminated with microcystins, and the toxin content was analyzed during growth. Whereas no difference in microcystins content was observed in cultivation with the chromosomally integrated strain, the yeast strain hosting the mlrA expression plasmid reduced 83% of toxins within 120 h of cultivation. Our results show microcystinase A expressed by industrial yeast strains as a viable option for practical applications in water treatment.