Today in 1998, US Patent 5716653 A was issued, an invention of Ronald E. Simard and Mohammed Bouksaim, for their “Process For Brewer’s Yeast Debittering.” Here’s the Abstract:

This invention relates to a process for debittering spent brewer’s yeast, aiming at maximal efficiency with minimal impact on yeasts for their further use as live cells. The process consists in bringing a yeast suspension in contact with a surfactant containing unsaturated fatty acids, like Tween 80® (0.2% to 20% v/v), adjusting pH to 10.0 with NaOH 2N and agitating during 5 minutes at 50 rpm and 50° C. A bitterness reduction of 98% is obtained, without affecting yeast viability or protein content. Furthermore, the debittered yeasts treated with 20% Tween 80® can be reactivated (viability of 100% and increased production of CO2) by growing them in a suitable medium for a sufficient time (about two to six hours). These reactivated yeasts have restored biological properties which are expected to allow the use of these spent yeasts in complete or partial replacement of new yeasts in bakery industry and in spirit and beer fabrication. This application for an industrial by-product brings a plus-value by exploiting its biological activity and its nutritional value and furthermore, represents an interesting solution for an environmental problem.

So essentially this idea is to take yeast after it’s been used in brewing beer, removing any bitter compounds and then using it again to bake bread. I know in England, at Marston’s in Burton-on-Trent, for example, sells their spent yeast to the nearby plant that makes Marmite, and is similar to the Australian Vegemite.