Bacterial degradation of natural and synthetic rubber

The degradation of natural rubber (NR), synthetic poly(cis-1,4-isoprene) (S R), and cross-linl<ed NR (latex gloves) by Gram-positive and Gram-negative bacteria was analyzed by weight loss, gel permeation chromatography, and de termination of the protein content. Weight losses of 11-18% and an increase in protein up to 850 <mu>g/mL after incubation of Nocardia sp. DSMZ43191, Streptomyces coelicolor, Streptomyces griseus, bacterial isolate 18a, Acine tobacter calcoaceticus, and Xanthomonas sp. with latex gloves as a carbon s ource indicated degradation of the polymer. An increase of protein up to 12 50 mug/mL was obtained upon incubation of the bacteria with SR. No or only little weight losses and no increase in the protein content were found for nondegrading control strains such as Streptomyces lividans and Streptomyces exfoliatus and for mutants of degrading strains of S. coelicolor and S. gr iseus, which have been identified by their inability to produce clearing zo nes on opaque latex agar. Measurement of the average molecular weight of sy nthetic rubber before and after degradation showed a time-dependent shift t o lower values for the degrading strains. Diketone derivates of oligo(cis-1 ,4-isoprene) were identified as metabolites of rubber degradation. An oxida tive degradation pathway of poly(cis-l,4-isoprene) to acetyl-coenzymeA and propionyl-coenzymeA by beta -oxidation is suggested for bacterial degradati on of isoprene rubber.