Method for the identification of a metabolic pathway family by means of positive selection

A method for selecting or preparing cells comprising at least one metabolic pathway or metabolic pathway family enabling the transformation of one or more substrate(s) {Ai} into a desired product {B}, comprising the following steps:

• a) providing a population of host cells (Ai−;
• B−) incapable of metabolizing said substrate or substrates {Ai} and said product {B};
• b) transforming said population of host cells with a library of sequences of nucleic acid;
• c) testing in parallel said population of transformed host cells on minimum media containing either one of the substrates {Ai}, or said product {B} as the only source of an element essential to growth;
• and
• d) selecting said host cell(s) capable of growth on a minimum medium containing one of the substrates {Ai} and on a minimum medium containing said product {B} (Ai+;
• B+).

A process for preparing the product {B} from the substrate {Ai} comprising:

• cultivating a host cell incapable of growth on a minimum medium containing one of the substrate(s) {Ai} and capable of growth on a minimum medium containing said product {B} (Ai−;
• B+);
• or
• cultivating a host cell that has been selected on the basis that it has become:
• incapable of growth on a minimum medium containing one of the substrate {Ai} and on a minimum medium containing said product {B} (Ai−;
• B−);
• and accumulates the product {B} when grown on a rich medium containing the substrate {Ai};
• and
• recovering the product {B}.

A method for selecting or preparing a host cell (Ai−;

• B−) incapable of metabolising said substrate(s) {Ai} and said product {B} comprising the following steps:
• testing a population of host cells, cultivatable under standard laboratory conditions and under industrial production conditions, transformable, and capable of stably maintaining the transforming exogenous DNA, on a minimum medium containing the substrate(s) {Ai} and said product {B} as the only source of an element essential to growth;
• and,
• selecting the host cell(s) incapable of growth on said minimum medium containing the substrate(s) {Ai} and said product {B}.