A chemiluminescence study on degradation of gelatine: Biodegradation by bacteria and fungi isolated from cinematographic films

Chemiluminescence (CL) has become a sensitive tool for the study of polymer degradation, induced by exposure to various factors, such us heat, UV-light and oxygen. In this paper, the results obtained with this technique in the study of gelatine samples hydrolytically degraded under sterilisation conditions are presented. Also, photographic gelatine exposed to bacterial and fungal degradations, in water solution and under controlled conditions, have been study by the chemiluminescence emission of their corresponding films and the biodegradation extent was determined by viscosity. The bacteria and fungi employed in this work have been isolated from cinematographic films in a previous work.The high intensities of chemiluminescence emission obtained for gelatines biodegraded by bacteria and fungi, in aqueous solution at 37 and 25 °C, respectively, are different to those obtained in the thermal degradation. The hydrolytic degradation mechanism is through a cleavage of the peptide bond of the protein without significant oxidation of the material. In contrast, biodegradation by bacteria and fungi at low temperatures decreases the molecular weight of the gelatine (viscosity) by the enzymatic activity but, also, produces an important oxidation in the material due to the reactive oxygen species (ROS) generated in the microbial metabolism.