Which yeast reproduces by fission rather than budding?

Schizosaccharomyces is unique among these yeast options because it reproduces by fission, a process whereby the yeast cell divides into two smaller cells. This method contrasts with the more common budding process seen in many other yeast species, including those in the other options listed.

In budding, a new cell develops from the outgrowth of a parent cell. While other options like Brettanomyces and Saccharomyces pastorianus also reproduce via budding, Schizosaccharomyces stands out due to its fission method, which involves cell elongation and splitting, typically seen in the fission yeast family. This distinct reproductive process is often highlighted in the study of yeast biology, especially regarding fermentation practices and applications in brewing and baking.

Pichia, while also interesting in its own right, primarily reproduces via budding. Thus, Schizosaccharomyces is recognized specifically for its fission reproductive strategy, making it the accurate choice in the context of the question.