Treatment of natural rubber waste by microorganisms

Nocardia sp. strain 835 A, capable of utilizing natural rubber as a sole carbon source, was used for treatment of rubber waste (latex gloves). Cultivation was performed in a laboratory fermenter with a working volume of 3.0 liter, stirring by a impeller at 450_??_500 rpm. Aeration rate was 3.5_??_4.0literfmin. Temperature was 30°C and pH was kept at 7.0 by addition of 2N NaOH. In batch cultures, 20g of rubber films were cut from latex gloves (New Doctor Hand, FujiLatex Co., Ltd.) and added into 3liter of a mineral salt medium. All over the film surface was covered uniformly by colonizations of rubber degrading cells of strain 835A after 25 days, and the rubber films were completely degraded after 45 days. In semi-continuous culture conditions, 2.5g of rubber films were added every 5 days into 3 liter of the medium, and 375ml of the culture medium were replaced with fresh medium at the same time. The culture was continued over 150 days without sterilization of rubber and medium. Uniform colonizations of strain 835 A over the film surface was obtained after 5 days cultivation, and the rubber films were completely degraded within 20 days. Under the same conditions, up to 10g of rubber added every 5 days was completely degraded. Cellular biomasses and water soluble organic materials produced from rubber were much less in semi-continuous cultures than those in batch cultures, and 50 to 80% of the microbial cells in semi-continuous cultures were precipitated after standing for 2 hr.