Biological degradation of natural rubber glove by gram negative bacteria Klebsiella aerogenes

Abstract

Abstract As the urgency and the scope of the global threat posed by the rubber waste is increasing, so have the efforts to find sustainable and efficient solutions. In recent years, biological degradation of rubber waste has been gaining interest as an alternative to conventional waste management practices and widely used chemical methods. The gram-negative bacteria Klebsiella aerogenes was used in the current study to perform natural glove rubber (NGR) degradation. Parameters such as fermentation duration (within 21 days), temperature (30, 35 and 40oC) and pH (6,7 and 8) on the effect of biodegradation was investigated. The biodegraded rubber was characterised by dry weight analysis which showed a maximum weight loss of 17% at pH 7 under 35oC after 21 days. The growth curve analysis showed that a maximum cell concentration of 4.12 g/L in week 2 of the biodegradation process. Increase in viable cell count over the incubation time indicated that rubber waste had suitable carbon source to sustain the culture during the biodegradation process. The visual confirmation of biodegradation was carried out by Schiff’s staining indicating the formation of aldehydes and ketones. Further confirmation on the presence of new aldehydes and ketones peaks were shown in FTIR analysis. Results also showed that highest protein concentration of 657.02 µg/ml and enzyme (laccase and Manganese peroxidase) activity of 0.43 ± 0.05 IU was observed at week 2 of the biodegradation. The experiment results concluded that Klebsiella aerogenes had the highest rubber weight loss in shorter period. This paper is first to report the presence of laccase and MnP enzymes in Klebsiella aerogenes. The bacteria Klebsiella aerogenes is efficient in degrading rubber in a shorter period, further analysis on the biodegradation pathway (mechanism) is worth investigating.