Brewer's spent grain and crude glycerol: Sustainable substrates for 2-phenylethanol production by Yarrowia lipolytica.

The development of natural, efficient, and cost-effective methods for producing the aromatic alcohol 2-phenylethanol (2-PE) is necessary. 2-PE, characterized by a rosy scent, is widely used in the cosmetic, pharmaceutical, and food industries. It is commonly utilized as a flavoring agent in desserts, baked goods, and beverages, enhancing the overall flavor with fruity, honeyed, creamy, and caramelized notes. In this study, the optimization of 2-PE production through fermentation of the yeast Yarrowia lipolytica on brewer's spent grain (BSG) was examined using a central composite design. The impact of crude glycerol (CG) and yeast extract (YE) on 2-PE production were investigated. A prerequisite for utilizing BSG as a substrate is the hydrolysis of its complex components, primarily starch. This was achieved by transforming the amyloglucosidase (AMG) gene into the genome of Y. lipolytica. Fermentations were carried out in 500 mL baffled Erlenmeyer flasks with a working volume of 100 mL. Optimally, 1.52 g/L of 2-PE was produced after 168 h fermentation in a medium containing 2.87 g/L yeast extract and 45.9 g/L crude glycerol in BSG.