Abstract

Although many single bacterial isolates can attack natural rubber (NR) complete biological degradation has been rarely achieved. However, previously we have observed that a mixed polymer of NR and starch could be completely degraded by a single species. Appropriate conditions need to be found to allow for complete access of the bacteria or their enzymes to all the double bounds of the hydrophobic chains of the isoprene units. It may be possible to develop a special consortium of bacteria in which different bacterium relies, to some extent, on the abilities of others for survival and together they can facilitate access for the de degrading enzymes. Thus they can attack all the double bound sites and also metabolize any potential growth inhibitors. There are many known bacterial consortia that can completely metabolize complex mixtures of plant materials, such as the consortium present in the rumen of herbivores. We have shown that a microbial consortium enriched from various soil samples incubated over a 30-day period in a mineral salts medium with standard pieces of rubber gloves as the sole carbon source and ammonium sulphate as the nitrogen source can degrade NR far more rapidly than a single isolate. A comparison of the degradation of standard pieces of rubber gloves by a single species and our consortium is shown by Scanning Electron Microscopy (SEM) photographs. The consortium and the single isolate had reduced the weight of the rubber product by approximately 33.4 and 10%, respectively, after 30 days. In addition, bacterial community changes were observed by plating out the culture at increasing times onto 3 different media. The different media used were nutrient agar (NA), MSM with rubber latex (MSM-NR) and potato dextrose agar (PDA). On the plates, mixed colonies types appeared along the time with different dominant colony types. The dominant colony types were isolated and are under identification by biochemical and molecular methods. In addition, the different organisms present in the consortium degrading the rubber gloves, after about 10 days, were investigated using DGGE. The different bacteria detected by this method will be compared with the isolates obtained from the plate cultures and their individual roles identified. Eventually, we will attempt to reconstruct this natural degradation process.