Manus Biosynthesis has announced the development of an engineered bacterium and scalable fermentation process to make commercial quantities of the sought-after zero-calorie natural sweetener rebaudioside M for the first time. Known as Reb M, the molecule is one of a set of steviol glycosides produced by the stevia plant that are popular as noncaloric sweeteners to replace sugar and high-fructose corn syrup in soft drinks and foods. Most commercial stevia products are based on stevioside and rebaudioside A, which are the most abundant steviol glycosides. However, similar to some artificial sweeteners, these compounds have subtle unfavorable bitter and metallic off-tastes that become more pronounced at higher concentrations. Among the steviol glycosides, Reb M has been flagged as having the best overall taste profile and favorable properties for beverage and food processing, according to Manus Biosynthesis founder and chief executive Ajikumar Parayil. Yet its low levels in the stevia plant, at less than 0.01% of leaf weight, has made it difficult to source economically. Building on core technology developed by MIT’s Gregory Stephanopoulos and coworkers, Manus Biosynthesis has succeeded in demonstrating production of bulk amounts of Reb M in better than 95% purity and published results in a recent patent application (WO2016073740).