Production of labelled organic compounds

Isotopically labelled organic compounds (e.g. amino acids and sugars) are obtained in a biological photoproduction process comprising the steps of culturing, in a culture medium containing at least one simple labelled inorganic nutrient, a mutant strain of photosynthetic prokaryotic or eukaryotic species selected from cyanobacterial or microalgal species which are capable of producing a said organic compound, and recovering labelled organic compound produced by the mutant strain from the culture medium. Thus with the present invention it is possible to achieve continuous production of isotopically labelled organic compound over an extended period of time using relatively simple and hence inexpensive feedstuffs. (Author)