Artificial Rubber Mineralization by Co-Cultured Bacterial Strains Isolated from Rubber Plantation Area

Research Article

Austin J Environ Toxicol. 2016; 2(1): 1011.

Artificial Rubber Mineralization by Co-Cultured Bacterial Strains Isolated from Rubber Plantation Area

Muralidharan M and Krishnaswamy VG*

Department of Biotechnology, Stella Maris College, India

*Corresponding author: SVeena Gayathri Krishnaswamy, Department of Biotechnology, Stella Maris College, Chennai-87, Tamilnadu, India

Received: May 13, 2016; Accepted: June 12, 2016; Published: June 14, 2016


Synthetic plastics are extensively used in packaging of products like food, pharmaceuticals, cosmetics, detergents and chemicals. Approximately 30% of the plastics are used worldwide for packaging applications. This utilization is still expanding at a high rate of 12% per annum. Hence, the removal of plastic from the environment has become a very important problem. The objective of the present study was Mineralization of artificial rubber by co-cultured Bacterial strains isolated from rubber plantation soil. Co-cultured bacterial strains had the capacity to mineralize plastic and Bioplastics. Mineralisation of the artificial rubber and plastics were confirmed by Spectrophotmetric and Fourier Transform Infra- Red (FTIR) studies. Artificial rubber, plastics and bioplastics degraded by the co-cultures were studied at different concentrations. Mineralization of artificial rubber was maximum (6.48 x 10-5) on the 20th Day. The co-cultured bacterial strains were identified as Bacillus cohnii and Brevundimonasnae jangsanensis. Further the Co-cultured bacterial strains were applied for the treatment of plastic and bioplastics which was confirmed by SEM analysis. Hence such isolated cocultures can be applied in the removal of artificial rubber, plastics and bioplastics present in the contaminated environment.

Keywords: Bacillus cohnii; Brevundimonasnae jangsanensis; Artificial rubber; Bioplastics; Mineralisation


In recent years, the waste disposal problem has spurred mounting interest in the biodegradability of polymers, especially when the public is voicing greater concern about protecting human health and preserving the quality of our environment. Rubber and plastics, for instance, that became an integral part of contemporary life, already formed a significant part of wastes in municipal landfills. Concerns regarding the environmental impact of solid wastes, recycling and composting options are expected to increase as landfill capacity decreases. Managing waste is thus a challenge facing the global community.

Today, plastics are utilized in more applications and they have become essential to our modern economy. The plastics industry has benefited from 50 years of growth with a year on year expansion of 8.7% from 1950 to 2012. In the medical and safety area, plastics are enabling major breakthroughs. The latest medical techniques use plastics to unblock blood vessels, develop artificial corneas or hearing devices to name but a few. Plastics are indispensable for protection equipment such as helmets, firemen suits or bullet proof jackets. Plastics have made it possible for us to push the limits and go further, faster and safer than we have dared to go before [1].

Bioplastics are plastics derived from renewable biomass sources, such as vegetable fats and oils, corn starch, pea starch or microbiota. Bioplastics can be made from agricultural by products and also from used plastic bottles and other containers using microorganisms. Common plastics, such as fossil-fuel plastics (also called petrobased polymers), are derived from petroleum. Production of such plastics tends to require more fossil fuels and to produce more greenhouse gases than the production of biobased polymers (Bioplastics). Some, but not all, bioplastics are designed to biodegrade. Biodegradable bioplastics can break down in either anaerobic or aerobic environments, depending on how they are manufactured. Bioplastics can be composed of starches, cellulose, biopolymers, and a variety of other materials [1].

As these plastics and rubber are not biodegradable, dumping of these causes grave threat to human health and environmental pollution. Thus it is the need of the hour to work on the degradation aspects of these polymers. Synthetic plastics like polyester polyurethane, polyethylene with starch blend, are biodegradable, although most commodity plastics used now are either non-biodegradable or even take decades to degrade. This has raised growing concern about degradable polymers and promoted research activity world wide to either modify current products to promote degradability or to develop new alternatives that are degradable by any or all of the following mechanisms: biodegradation, photodegradation, environmental erosion and thermal degradation [2].

Due to similar material properties to conventional plastics [3,4] the biodegradable plastics (polyesters), namely Polyhydroxyalkanoates (PHA), polylactides, polycaprolactone, aliphatic polyesters, polysaccharides and copolymer or blend of these, and have been developed successfully over the last few years. The most important are poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3- hydroxyvalerate). Bioplastics (Biopolymers) obtained from growth of microorganisms or from plants which are genetically-engineered to produce such polymers are likely to replace currently used plastics at least in some of the fields [5].

Microorganisms such as bacteria and fungi are involved in the degradation of both natural and synthetic plastics [6]. The biodegradation of plastics proceeds actively under different soil conditions according to their properties, because the microorganisms responsible for the degradation differ from each other and they have their own optimal growth conditions in the soil. Polymers especially plastics are potential substrates for heterotrophic microorganisms [7].

Hence, the present study focuses on the mineralization of artificial Rubber and bioplastics by co-cultured bacterial strains isolated from contaminated soil of rubber plantation area. The mineralization of artificial rubber and bioplastic material was evaluated by FTIR studies and Scanning electron microscopic observations. Such isolated Co-cultured bacterial strains shall be applied in the treatment of contaminated soild wastes sites harbouring artificial rubber and synthetic polymer.

Materials and Methods

Bacterial co-cultures and culture preparation

Bacterial co-cultures were isolated from contaminated soil of rubber plantation area was initially adapted and enriched with natural rubber and artificial Rubber (Latex Glove) as the sole carbon source. There were about two bacterial strains, which were enriched and isolated. These bacterial strains were identified by 16s RNA sequencing and the results showed that the bacterial strains belong to Bacillus cohnii and Brevundimonasnae jangsanensis [8].

Bacterial co-cultured strains was grown 150ml mineral salts medium prepared in conical flasks with the composition: Dipotassium hydrogen phosphate (K2HPO4) - 1g/L, Magnesium sulphate (MgSO4.7H2O) - 0.5g/L, Potassium nitrate (KNO3) - 1g/L [9].

Cell morphology and the motility of cells in exponentiallygrowing liquid cultures were examined on freshly-prepared wet mounts by light microscopy. Plate counting (cfu/mL) was done on nutrient agar medium. The Bacterial co-cultures were studied for its growth on artificial rubber gloves, Plastic and bioplastic material as the sole carbon source. For the mineralisation study, mineral medium containing artificial rubber /Plastic/Bioplastic was inoculated with the bacterial co-cultures. Different conditions used for the degradation of phenol were (i) medium + Artificial rubber/ Bioplastic + Bacterial cocultures; (ii) medium + Artificial rubber/ Bioplastic and (iii) medium + bacteria co-cultures , with (ii) and (iii) serving as controls. The bacterial consortium was added to the medium at concentrations of 105 - 106 cfu/mL. The culture, in duplicate, was incubated at 37°C with shaking at 150 rpm and samples were withdrawn at 24 hours interval for 5-days. Then further sub culturing was done at 24 hours interval. The two bacterial strains, which were capable of degrading Natural rubber latex Bacillus cohnii and Brevundimonasnae jangsanensis, were used for the degradation of artificial rubber, Plastics and Bioplastics.

Mineralization of polymers by the bacterial cocultures

To study the mineralization of artificial rubber (Latex glove) was used as the substrate to study the mineralization. To 150 ml of Mineral Salts Medium 3mm of artificial rubber strips were added and logarithmic phase co-cultured bacterial isolates were inoculated and incubated at 37°C in Orbital shaker at 150 RPM. (Figure 1) shows the experimental set-up of the mineralization study. In the same way 3 mm strips of plastics and bioplastics were added in each of the conical flasks in duplicates and anlaysed for the mineralization. The polymer strips were examined for mineralization by viewing in Binocular light microscope, Dark field microscope and Scanning electron Microscopy for a period of 30 Days. Further mineralisation of the artificial rubber, Plastics and Bioplastics were confirmed by analysing the compounds released during the mineralization by performing FTIR spectroscopy and Scanning electron Microscopy.