* First burger cost 250,000 euros and 5 years of research
* Tasters say texture was good, but note "absence of fat"
* Demand for meat seen increasing by 73 percent by 2050
By Kate Kelland, Health and Science Correspondent
LONDON, Aug 5 (Reuters) - The world's first laboratory-grown beef burger was flipped out of a petri dish and into a frying pan on Monday, with food tasters declaring ...