But in the intervening decades, new genetic technology has made it easier to search for enzymes that would convert A and B blood more effectively and efficiently into O, Withers said.
He and his colleagues looked at enzymes made by intestinal bacteria because the types of sugars that define A and B blood are present on the intestinal wall. Bacteria are known to divert part of their energy from the breakdown of these sugars, Withers said.
The research team found an enzyme that seems to cut the A-type sugar in a "very specific" way, he said.
Specificity is important because, if the enzyme makes other changes in the cell, this could cause an immune response in recipients, Withers said.
"We do not seem to see any other sugars cut off by this enzyme, which is really important because we do not want to change the red blood cell in any way that could endanger it," Withers said. "As far as we can see, we only cut off the A antigen."
The researchers have applied for a patent, and are not inclined to talk about which specific intestinal bacteria the enzyme will produce until it is approved, he said.
The next step is to use a protein technique called "targeted evolution" to simulate the accelerated natural evolution in the bacteria, with the aim of creating the most efficient sugar-removing enzyme, Withers said.
Dr. Pampee Young, chief medical officer of the American Red Cross, said that this kind of innovation, if it proves effective, would help to strengthen the "constant" need for blood.
"Every second second someone in the US needs blood," Young said. "The Red Cross needs to collect more than 13,000 blood and platelet donations daily to meet the needs of accident victims, people undergoing cardiac surgery, cancer patients, people with blood disorders and others.
"The approach presented is innovative and interesting," Young said of Withers' technology. "We are hopeful that technology can help relieve many of the problems related to blood shortages at blood collection centers such as the Red Cross and others to meet the needs of the patient.
"We monitor the progress of innovations as they are validated, prepared for clinical use and when safety and efficacy are established," Young concluded.