Saccharomyces cerevisiae, an essential player in alcoholic fermentation during winemaking, is rarely found in intact grapes. Here, we addressed symbiotic interactions between S. cerevisiae and grape-skin residents upon spontaneous wine fermentation. When glucose was used as a carbon source, the yeast-like fungus Aureobasidium pullulans, a major grape-skin resident, had no effect on alcoholic fermentation by S. cerevisiae. In contrast, when intact grape berries as a sole carbon source, coculture of S. cerevisiae and A. pullulans accelerated alcoholic fermentation. Thus, grape-inhabiting microorganisms may increase carbon availability by degrading and/or incorporating grape-skin materials, such as cell wall and cuticles. A. pullulans exhibited broad spectrum assimilation of plant-derived carbon sources, including ω-hydroxy fatty acids, arising from degradation of cutin. In fact, yeast-type cutinase was produced from A. pullulans EXF-150 strain. The degradation and utilization of grape-skin materials by fungal microbiota may account for their colonization on grape-skin and symbiotic interactions with S. cerevisiae.