The pollution of the environment by plastics is a perpetual problem that poses a great challenge to mankind. A promising strategy to counteract the increasing pollution is the innovation and development of biodegradable materials. However, biodegradable plastics reach into the marine environment in the same way as conventional plastics and can also be ingested by marine organisms. There is a wide variety of different polymers that are used in biodegradable materials, such as polylactic acid (PLA), polybutylene succinate (PBS) or polyhydroxyalkanoates (PHAs). Those compounds are known to be enzymatically degradable by several enzymes under certain conditions. Once ingested by marine organisms such as crustaceans, the highly active mixture of enzymes in their digestive tracts may break down compounds and facilitate degradation. In this study, the hydrolytic activity of gastric fluids from Cancer pagurus on different biodegradable and conventional plastics was evaluated with pH Stat titration. The enzymes capable of hydrolyzing biodegradable plastics were isolated from the gastric fluid and characterized using several analytical methods. Separated protein fractions with a high amount of lipolytic enzymes showed the highest potential on hydrolyzing biodegradable plastics.