Biodegradation of cinematographic gelatin emulsion by bacteria and filamentous fungi using indirect impedance technique

The biodegradation of black and white photographic gelatin emulsion by bacteria and fungi was studied by indirect impedance technology. The presence of silver on the emulsion (black films) inhibited the microbial growth confirming the biocidal effect of the metallic silver. Biodegradation of commercial gelatines, linear and crosslinked (prepared using formaldehyde as crosslinking agent) by Bacillus subtilis was studied. The extent of crosslinking in the gelatin does not have any influence on the biodegradation rate. Through the accumulated amount of CO2 produced with bioassay time and the corresponding percentage of biodegradation reached, the relative biodegradation efficiency of the bacteria and fungi was evaluated. The six studied bacteria (five strains of Bacillus and one Staphylococcus) were effective in their ability to biodegrade the photographic emulsion with different CO2 production rates. Two of them, B. subtilis and B. megaterium showed an exponential rate of biodegradation and reaching 55% of CO2 conversion. Also, all the studied fungi, nine strains, were found to biodegrade the emulsion with Penicillium chrysogenum being the more efficient fungus showing 30% of emulsion biodegradation in 3 weeks.