The use of flocculating yeast strains has been considered as a convenient approach to obtain high cell densities in bioreactors with increasing productivity in continuous operations. In Kluyveromyces marxianus ATTC 10022, the GAP1 gene encodes an isoform of glyceraldehyde-3-phosphate dehydrogenase-p37-that is accumulated in the cell wall and is involved in flocculation. To test the use of p37 as a tool for engineering Kluyveromyces cells to display a flocculation phenotype, K. marxianus CCT 3172 was transformed with an expression vector containing GAP1. This vector is based on the pY37 previously described, harbouring a S11 Kluyveromyces origin of replication, and the expression of GAP1 is under the control of GAL1. Kluyveromyces cells overexpressing GAP1 acquired a flocculent phenotype together with the accumulation of p37 in the cell wall. The results support the use of GAP1 gene as a molecular tool for inducing flocculation.