Brevibacillus parabrevis, Acinetobacter baumannii and Pseudomonas citronellolis - Potential candidates for biodegradation of low density polyethylene (LDPE)

Abstract

Low density polyethylene is one of the polymers that is up till date nearly impossible to be degraded safely. Biodegradation is the safest method of breakdown that possibly leaves behind less toxic residue and shows potentials of bio-geo chemical cycling of the substrate. Considerable amount of work has been carried out in this area, but most of them are associated with blended low density polyethylene (LDPE). Previous reports also rely on host consortia for degradation. Various techniques have been implicated in designing this kind of study. BATH test, to evaluate the hydrophobicity of the isolates was performed apart from the calculation of generation time of the isolates in LDPE incorporated growth medium. Biofilm formation was also quantified by using protein estimation technique. Our findings corroborated previous findings in most of the techniques, but in Sturm test, a technique to evaluate concentration of carbon dioxide, a final product of biodegradation of LDPE, we have taken dissolved CO2 (that is, CO2 present in the soluble form in the growth medium, apart from the gaseous CO2 collected in the KOH tube) also in consideration which is not reported by any of the previous workers. The current article investigated the biodegradation ability of bacteria isolated from a municipal landfill area near Pallikaranai, Chennai, South India. The bacteria were subjected to growth in a medium containing LDPE as the sole carbon source with and without a nitrogen source. Four bacterial species were isolated. According to the 16S rRNA gene sequences they were identified as Brevibacillus parabrevis (PL-1), Acinetobacter baumannii (PL-2, PL-3) and Pseudomonas citronellolis (PL-4). Bacterial adhesion to hydrocarbon (BATH test) was done to determine the bacterial hydrophobicity. Bacterial biomass was quantified to estimate the population density of the biofilm. This work clearly identifies with our objective to find a right microbe to degrade the resistant LDPE by giving out promising results from the present study. Key words: Biodegradation, low density polyethylene (LDPE), bacterial adhesion to hydrocarbon (BATH test), sturm test, Pseudomonas, Acinetobacter, Brevibacillus.