Direct and efficient elimination of ethyl carbamate by engineered Saccharomyces cerevisiae displaying urethanase

Abstract

Ethyl carbamate (EC) is a probable human carcinogen (Group 2A) that is naturally formed in fermented foods and alcoholic beverages. In this study, the feasibility of using engineered Saccharomyces cerevisiae strains capable of eliminating EC regardless of its pathway of formation was explored. The gene coding for urethanase (UreA) from Micrococcus species, which can directly convert EC into ethanol and ammonia, was introduced into S. cerevisiae. While the S. cerevisiae strain expressing intracellular UreA degraded only 44.5 mg/L EC, the engineered strain expressing extracellular UreA (MFαSP-UreA) exhibited a much-elevated degradation (341 mg/L) after 84 h. The EC degradation activity of S. cerevisiae was further enhanced by displaying UreA on the yeast cell surface. Specifically, the S. cerevisiae strain displaying UreA (EBY100/Aga2-UreA) using a-agglutinin as an anchoring motif degraded 476 mg/L EC, which was 31% higher than that of the strain expressing MFαSP-UreA. In a bioreactor fermentation batch at pH 5.0 (the optimal pH for UreA activity), the EBY100/pAga2-UreA strain degraded 519 mg/L EC in 84 h. Therefore, this study highlights the benefits of surface display of enzymes to enhance the degradation of toxic compounds by engineered strains of S. cerevisiae. © 2022 Elsevier Ltd