Marine sponges are extremely rich in natural products and are considered a promising biological resource. The major objective of this work is the coupling of a green extraction process with a natural origin renewable raw-material to obtain sponge-origin collagen/gelatin, particularly for biomedical applications. Marine sponge collagen has unique physico-chemical properties but its application is hindered by lack of availability due to inefficient extraction methodologies. Traditional extraction methods are time consuming as they involve several operating steps and large amounts of solvents. Alternatively, the use of subcritical water for the extraction of collagen can appear as a highly relevant methodology. It has been proposed before for the extraction of collagen from fish scales. However, the process conditions are extreme (high temperature and pressure) conducting to the denaturation degradation of collagen, which occurs above 37ºC for human collagen. In this work, we propose a new extraction methodology, under mild operating conditions, in which water is acidified with CO2 to promote the extraction of collagen/gelatin from different marine sponge species