The biological attack of microorganisms on rubber materials was investigated in order to evaluate possible contributions of biotechnology for refinement and recycling of used rubber products. Adaptation of microbial enrichment cultures with tire crumb material for several months resulted in enhanced growth of microorganisms especially on NR and on SBR, In order to elucidate general mechanisms of bacterial action on hydrophobic substances like rubbers, different kinds of polyisoprenes were chosen for further examination. The polyisoprenoids were employed as sole nutrient source for enrichment of microorganisms that show considerable deterioration of the materials and enhanced mineralization of the rubber hydrocarbon.