An Aspergillus nidulans transformant expressing the Trichoderma longibrachiatum endoglucanase 1 gene (egl1) has been constructed. The extracellular production of EGL1 in different culture media has been studied, and a medium has been found in which EGL1 is the predominant extracellular protein produced. The enzymatic properties of the heterologously produced EGL1 are very similar to those of the native enzyme. Grape maceration in the presence of culture filtrate enriched in EGL1 resulted in increased release of aroma precursors, particularly in the case of aromatic grapes. Cryoscanning electron microscopy of the flesh of grapes treated with EGL1-enriched culture filtrate revealed degradation of the cell wall matrix.