Biodegradation of Chemically Modified Gelatin Films in a Simulated Natural Environment

ABSTRACT

Modified (crosslinked) gelatin films were prepared using various crosslinking agents: formaldehyde, butadiene diepoxide and hexamethylene diisocyanate. They were evaluated for their biodegradability by exposing them to sewage, which was inoculated with periphyton taken from the bottom and walls of municipal sewage systems. Biodegradability was assessed by weight loss of the films and by means of total dehydrogenase activity of the biomass, taken from the surface of the films. Biodegradation was apparent both in uncrosslinked gelatin and in the crosslinked samples. The gelatin crosslinked with hexamethylene diisocyanate degraded fastest (complete degradation in 5 days), followed by uncrosslinked gelatin and gelatin crosslinked with butadiene diepoxide (complete degradation in 10 days). The most stable was the formaldehyde crosslinked gelatin—complete degradation only in 20 days. The dehydrogenase activity increased rapidly up to the 7th day, and then dropped. It paralleled the biodegradation of gelatin and could be used as a measure of biodegradability of crosslinked gelatin, and probably other biodegradable polymers. The periphyton on the surfaces of the films was found to be molds, actinomyces, yeast and bacteria. Various kinds of algae were observed as well, specifically flint algae, brown algae, blue-green algae, and filamentous green algae.