At the University of Zagreb in north-central Croatia, associate professor of biochemistry Igor Stuparević, PhD, explores many aspects of the biology and biotechnological use of yeast, especially Saccharomyces cerevisiae. In fact, Stuparević began studying yeast years ago. Recently, Stuparević and his colleagues reported on one application of yeast surface display, which is a method that can be used for improving many features in the development of a bioprocess.

“Yeast surface display can turn yeast cells into living biocatalysts by displaying enzymes on their surface, allowing direct interaction with substrates that would otherwise not cross the cell membrane,” Stuparević explains. “This makes them particularly valuable for high-throughput screening and continuous monitoring of enzyme activity in real time.” Stuparević also points out that the flexibility of the system enables the screening of enzyme variants and their inhibitors, which supports the optimization of enzyme-based processes, such as fermentation, drug synthesis, or industrial biocatalysis.

Novel protocol

Stuparević and his colleagues developed a protocol for quantifying the enzyme β-lactamase, which is displayed on the cell wall of genetically engineered S. cerevisiae. Subsequently, spectrophotometric analysis at 482 nm can be used to quantify the activity of β-lactamase, which hydrolyzes the antibiotic nitrocefin. This system can therefore be used to monitor the enzyme’s activity, as well as its kinetics or the effects of inhibitors.

When asked how this system could be used in bioprocess development, Stuparević points out four key benefits: cost efficiency, sustainability, real-time monitoring, and high-throughput potential.

In terms of cost, Stuparević notes that, “the use of live yeast cells as biocatalysts reduces the need for enzyme purification and immobilization steps, which are often expensive and labor-intensive.” In addition, this system is sustainable, because it “enables the repeated use of the same yeast culture by displaying enzymes on the cell surface, simplifying the bioprocess by eliminating the need for constant enzyme replenishment,” he explains. Real-time monitoring, Stuparević says, “is essential for optimizing reaction conditions and improving process yield.”

Many bioprocessors seek high-throughput systems for development, and this approach based on yeast surface display provides that opportunity. As Stuparević puts it: “The system is highly adaptable for screening large libraries of enzyme variants or inhibitors, making it a powerful tool for process optimization and drug discovery.”