Yeast as a tool for exploring disulfide-rich peptides.

Cyclic disulfide-rich peptides have become increasingly popular in drug development because their structures enhance molecular stability and allow for mutagenesis to introduce non-native functions. This review focuses on yeast-based platform technologies and their utility in advancing cyclic disulfide-rich peptides as drug modalities and for large-scale biomanufacturing. These technologies include yeast surface display which facilitates the screening of large libraries to develop peptide binders with strong affinity and selectivity for protein targets, while maintaining the innate high stability of the peptide scaffold via protease-based selection pressure. We also describe a recently developed platform that leverages yeast's ability to secrete correctly folded disulfide-rich peptides while simultaneously displaying peptide or protein tags on their surfaces. In combination with microfluidics technology, the platform creates single-cell yeast-in-droplets reactors, enabling the screening of large libraries based on functional output rather than solely on binding affinity. After identifying cyclic peptide candidates through library-based discovery, these candidates can be produced using a versatile yeast-based bioproduction platform. Traditionally, cyclic disulfide-rich peptides are produced through solid-phase synthesis, a method that generates significant amounts of toxic waste. In contrast, yeast-based bioproduction offers an environmentally sustainable alternative. It has the capability to produce structurally distinct peptides with minimal adjustments and is easily scalable using microbial fermenters, making it an ideal choice for large-scale production.