Open (non-sterile) cultivations of Debaryomyces hansenii for recombinant protein production combining industrial side-streams with high salt content.

The halotolerant non-conventional yeast Debaryomyces hansenii can grow in media containing high concentrations of salt (up to 4 M), metabolize alternative carbon sources than glucose, such as lactose or glycerol, and withstand a wide range of temperatures and pH. These inherent capabilities allow this yeast to grow in harsh environments and use alternative feedstock than traditional commercial media. For example, D. hansenii could be a potential cell factory for revalorizing industrial salty by-products, using them as a substrate for producing new valuable bioproducts, boosting a circular economy. In this work, three different salty by-products derived from the dairy and biopharmaceutical industry have been tested as a possible feedstock for D. hansenii 's growth. The yeast was not only able to grow efficiently in all of them but also to produce a recombinant protein (Yellow Fluorescent Protein, used as a model) without altering its performance. Moreover, open cultivations at different laboratory scales (1.5 mL and 1 L) were performed under non-sterile conditions and without adding fresh water or any nutritional supplement to the cultivation, making the process cheaper and more sustainable. [Display omitted] • D. hansenii can thrive in high-salt containing feedstocks for producing recombinant proteins. • Side-streams with high salt content are used without sterilization in lab-scale fermentations. • No addition of fresh water to the media is needed, waste-streams can be used directly from the source. [ABSTRACT FROM AUTHOR]