There may be a new use for that urine you've been so thoughtlessly flushing. Scientists say it could be an alternate source of a valuable bone- and tooth-repair material, with a little help from a genetically modified type of yeast.
Hydroxyapatite is a naturally occurring calcium- and phosphorus-based mineral compound, and is the major component of bones and tooth enamel. It is thus utilized in implanted scaffolds used to mend broken bones, and in dental procedures for restoring weakened or damaged teeth.
In humans and other animals, hydroxyapatite is produced by specialized cells known as osteoclasts, which combine collected calcium and phosphate to form the compound. Unfortunately, because these cells are difficult to grow and support outside of the body, cultured hydroxyapatite tends to be quite expensive.
Yeast, on the other hand, is robust and easy to maintain. And what's more, a yeast named Saccharomyces boulardii functions much like an osteoclast, in that it scavenges minerals from its environment and stores them in a part of its body called the vacuole.
With this fact in mind, scientists from the Lawrence Berkeley National Laboratory set about genetically modifying S. boulardii to make it collect calcium and phosphate, then turn those minerals into hydroxyapatite. The resulting organism has been named "osteoyeast," and it can obtain everything it needs from freely-available urine.
It has a conversion efficiency rate of 1 gram of hydroxyapatite per kilogram of urine, which should likely improve as more research is conducted. The scientists estimate that in a city the size of San Francisco, it would cost about US$19 to produce 1 kg (2.2 lb) of the cultured hydroxyapatite, which could sell for anywhere from $50 to $200 in the US market.
It is hoped that the so-called "pee-cycling" technology could soon be put to use in sewage treatment plants. There, it could serve as both a source of revenue and a means of breaking down urine for easier, less costly removal from the waste stream.
A paper on the study, which also involved scientists from the University of California Irvine and the University of Illinois Urbana-Champaign, was recently published in the journal Nature Communications.
Source: Lawrence Berkeley National Laboratory