In the new study, the research team succeeded in engineering the yeast Yarrowia lipolytica to produce a precise mixture of six key sterols that bees need. This was then incorporated into diets fed to bee colonies during three-month feeding trials. These took place in enclosed glasshouses to ensure the bees only fed on the treatment diets.

Key findings:

• By the end of the study period, colonies fed with the sterol-enriched yeast had reared up to 15 times more larvae to the viable pupal stage, compared with colonies fed control diets.
• Colonies fed with the enriched diet were more likely to continue rearing brood up to the end of the three-month period, whereas colonies on sterol-deficient diets ceased brood production after 90 days.
• Notably, the sterol profile of larvae in colonies fed the engineered yeast matched that found in naturally foraged colonies, suggesting that bees selectively transfer only the most biologically important sterols to their young.