Newly discovered bacterial enzymes can be used to convert types A, B, and AB blood into universal donor types O blood (Liu QP et al. Nat Biotechnol. 2007;25:454-464).
The idea of using enzymes to convert types A, B, and AB blood cells to type O by cleaving antigenic monosaccharides from red blood cells (RBCs) dates back to the early 1980s, when scientists found that a similar enzyme derived from coffee beans could remove B antigens from the cells. However, the process was too inefficient to be practical and attempts to strip cells of the A antigen were not successful.
Stephenson J. Blood Simple. JAMA. 2007;297(19):2069. doi:10.1001/jama.297.19.2069-b