Recycling of spent heavy water from microbial cultivation and its application in glycine deuteration

Shibazaki, Chie; Oku, Takayuki   ; 5 of others*

The Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC) hosts numerous experiments on materials and life science research using neutron beams. In neutron scattering studies, deuterated samples are widely employed for selective labeling to extract localized information, contrast variation neutron scattering experiments, and to suppress incoherent scattering from hydrogen. However, the domestic price of heavy water (DO) in Japan has surged several-fold over the past decade, it is necessary for developing a new method for recycling spent DO solution into pure DO with a high concentration of heavy water at a low cost. In this study, we established a method to recycle DO from waste generated during microbial cultivation by removing impurities via distillation and activated carbon treatment, followed by electrolysis to enhance deuterium concentration. As a result, 3 L of spent DO (96.6%) solution was purified to yield 1 L of recycled DO (98.8%). Purity was confirmed using 31P and 1H NMR spectroscopy with no impurities detected. The recycled DO was effective in deuteration of glycine using a platinum on carbon catalyst and 2-propanol, with no inhibitory effects. We conducted similar deuteration experiments on several types of amino acids and successfully obtained amino acids with a high degree of deuteration. This approach reduces DO costs and promotes its reuse as a sustainable resource. In the future, we aim to develop methods for the full deuteration of amino acids with side chains, such as alanine and histidine, and to explore the functional properties of the deuterated peptides.