The non-conventional yeast Yarrowia lipolytica is widely investigated for its unusual metabolic properties. Among them is the ability of Y. lipolytica to adopt an ovoid or hyphal morphology according to environmental conditions. The mechanism of dimorphic transition involves numerous genes, which have been poorly documented to date. Here, we report on the isolation of a filamentous mutant from an insertion mutagenesis library, the subsequent identification of the mutated gene, and the use of this filamentous mutant in biofilm bioreactors