Coupling bacterial nitrogen fixation to yeast whole-cell biocatalysis enables amine production using air as the sole nitrogen source.

backgroundAlkylamine production depends on ammonium produced via the energy-intensive, fossil-based Haber-Bosch process. Diazotrophic bacteria could offer a biological alternative by supplying nitrogen directly from air to heterotrophic whole-cell biocatalysts for alkylamine production. However, their integration with yeast production systems remains largely unexplored.

resultsHere, we evaluated the use of an ammonium-excreting strain of Azotobacter vinelandii (AZBB664) to supply nitrogen to an engineered Saccharomyces cerevisiae biocatalyst for vanillylamine production using air as the sole nitrogen source. A modified Burk's medium was developed to support S. cerevisiae growth and enable evaluation of biologically supplied nitrogen. Co-cultivation of both organisms was feasible under diazotrophic conditions, however, vanillin oxidation by A. vinelandii prevented effective vanillylamine production. To address this, a sequential process was implemented in which A. vinelandii was first used to generate ammonium in a modified Burk's medium, followed by cell removal and use of the resulting medium (AZM1) for yeast cultivation. In this medium, the yeast strain CEN.PK 113-7d exhibited a growth rate of 0.27 h

conclusionsA. vinelandii-derived medium enables yeast growth and whole-cell reductive amination using air as the sole nitrogen source. This demonstrates that biologically fixed nitrogen can directly sustain heterotrophic whole-cell biotransformations, establishing a strategy for coupling diazotrophy with biocatalytic production systems.