Abstract
Natural rubber latex is one of the problems that raises the environmental concerns. In this study the degrading ability of Ficus elastica rubber latex by a bacterium strain ASU-03, isolated from Egyptian soil was assessed. The strain was able to produce clear zone around its colony on latex rubber containing medium and was identified by conventional methods as Streptomyces sp. Phylogenetic analysis of 16S rRNA (16S rRNA) and RNA polymerase ß-subunit (rpoB) genes were applied. Results of the 16S rRNA gene analysis revealed that the strain was highly related to Streptomyces sp. (100% similarity), so the rpoB gene was partially sequenced to clarify the specific name of the isolate. Phylogenetic tree based on rpoB gene sequences indicated that strain ASU-03 was highly similar to the reference strain Streptomyces labedae and both were shared a one cluster. The current results demonstrated that the use of a rpoB gene-based method gives a better resolution in the species level identification. To our knowledge, this species has never been reported to be involved in natural rubber degradation. This was therefore the first report about the degradation of Ficus elastic by S. labedae. The degradation of Ficus elastica rubber latex was determined by measuring the increase in protein content of bacterium (mg/g dry wt), reduction in molecular weight (g/mol) and inherent viscosity (dL/g) of the latex. Moreover the degradation was also confirmed by formation of aldehyde or keto group by Schiff’s reagent and by observing the growth of the Streptomyces strain using scanning electron microscopy.