Effect of pretreatment of rubber material on its biodegradability by various rubber degrading bacteria

The effect of pretreatment of several cis-l,4-polyisoprene containing rubbe rs on their biodegradability was examined. Tests were carried out with six recently isolated and characterized rubber degrading bacteria belonging to the genera Gordonia (strains Kb2, Kd2 and VH2), Mycobacterium, Micromonospo ra and Pseudomonas. All strains were able to use natural rubber (NR) as wel l as NR latex gloves as sole carbon source. Extraction of NR latex gloves b y organic solvents resulted in an enhancement of growth for three of the se lected strains. On the other hand, growth of Gordonia sp. (strain Kb2 and K d2), Mycobacterium fortuitum NF4 and Micromonospora aurantiaca W2b on synth etic cis-1,4-polyisoprene did only occur after removal of the antioxidants, that are usually added during manufacture to prevent aging of the material s. Detailed degradation studies performed with Gordonia sp. Kb? revealed an enhanced mineralization of pretreated NR latex gloves and mineralization o f purified natural rubber (NR), indicating the actual mineralization of cis -1,4-polyisoprene rubber constituent even after removal of non-rubber const ituent that may act as co-metabolic substrate and support microbial growth. Further analysis by scanning electron microscopy (SEM) clearly demonstrate d the enhanced colonization efficiency of these bacteria towards pretreated NR latex gloves. Colonization was additionally visualized by staining of o vergrown NR latex gloves with Schiffs reagent, and the purple color produce d in the area of degradation was an evidence for the accumulation of aldehy des containing oligomers. Further enhancement of latex gloves degradation c ould be achieved after successive replacement of mineral salts medium durin g cultivation. Thereby, a rapid disintegration of untreated NR latex gloves material was accomplished by Gordonia sp. strain VH2. (C) 2000 Published b y Elsevier Science B.V. All rights reserved.