A Diamine Oxidase from <i>Glutamicibacter halophytocola</i> for the Degradation of Histamine and Tyramine in Foods

• Published in: Foods
• Main Authors: Lucas Kettner, Alexander Freund, Anna Bechtel, Judit Costa-Catala, Lutz Fischer
• Format: Article
• Language: English
• Published: MDPI AG 2025-09-01
• Subjects: diamine oxidase; DAO; histamine; tyramine; histamine intolerance; biogenic amines
• Online Access: https://www.mdpi.com/2304-8158/14/17/3093

A novel diamine oxidase (DAO) was discovered in the bacterium <i>Glutamicibacter halophytocola</i> (DAO-GH). The gene of DAO-GH was integrated into the genome of the yeast <i>Komagataella phaffii</i> and recombinantly produced under control of the methanol-inducible AOX1 promoter in a bioreactor cultivation. A high DAO activity of 70.2 ± 5.2 µkat/L_culture (5.25 ± 0.22 µkat/g_protein) was yielded after 90 h of cultivation. The DAO-GH was partially purified by the polyethyleneimine precipitation of nucleic acids, fractionated ammonium sulfate precipitation and hydrophobic interaction chromatography, resulting in a specific DAO activity of 19.7 µkat/g_Protein. The DAO-GH was then biochemically investigated regarding its potential for histamine and tyramine degradation in fermented foods and the human small intestine. Interestingly, the DAO-GH showed activity even at a low pH of 5 and low temperature of 6 °C. Both histamine and tyramine were effectively degraded and DAO-GH showed especially very high affinity towards tyramine (<i>K</i>_m of 0.009 mM). The DAO-GH was shown to be capable of degrading around 20% of the initially applied histamine in tuna paste (pH 5.6) at 5 °C within 24 h and completely degraded the histamine in a simulated intestinal fluid within 1.5 h in bioconversion experiments. The DAO-GH was spray-dried for the production of a storable enzyme preparation. Only around 17% of activity were lost in this process and the DAO-GH remained stable at room temperature for at least 3 months. The discovery of this DAO with its very advantageous biochemical properties allows the preparation of histamine-reduced or -free fermented foods by a simple enzymatic treatment or the treatment of histamine intolerance symptoms as a dietary supplement or medicine.