Abstract: The invention concerns a method for preparing nucleic acids from an environment sample, more particularly a method for obtaining a library of nucleic acids from a sample. The invention also concerns nucleic acids of nucleic acid libraries obtained by said method their use in the synthesis of novel compounds, in particular novel compounds of therapeutic interest. The invent further concerns novel means used in the method for obtaining said nucleic acids, such as novel vectors and novel processes for preparing such vectors or recombinant host cells containing said nucleic acid. Finally, the invention concerns methods for detecting a nucleic acid of interest within a library of nucleic acids resulting from said method, and nucleic acids detected by said method and polypeptides encoded by said nucleic acids.

Abstract: The present invention relates to a plasmid vector for cloning and expression of a protein in a microorganism, which comprises at least one structural gene which codes the synthesis of the said protein and elements which ensure the expression of the said structural gene in a microorganism, and wherein the promotion of the structural gene is ensured by the expression promotor of the .beta.-glucosidase gene in yeasts.The present invention also relates to microorganisms transformed by the said vectors, in particular a transformed strain of S. cerevisiae, a fermentation process using the said vectors, and the enzymes prepared by the said process, in particular .beta.-glucosidase.