Biotic oxidation of polyethylene using a bio-surfactant produced by B. licheniformis: a novel technique

Abstract

Polyethylene was incubated with a bio-surfactant producing bacterium B. licheniformis for 2 months in a suitable media. Low concentrations of NaCl were added to study its effect on the bio-surfactants activity. Being amphiphilic, the surfactant has a unique ability to decrease the surface energy, and this decrease measured using the surface tension of the medium was 50%. The surfactant was able to oxidize both control (unoxidized) and pre-oxidized polyethylene during incubation. The oxidation level of the control polyethylene sample was increased in the presence of NaCl, and the oxidation level was higher in the presence of 1% NaCl as compared to that found with 0.5% NaCl. A higher amount of surfactant was also produced, as observed by the comparatively low surface tension in the presence of NaCl. During the bio-oxidation of polyethylene, higher amounts of unsaturated hydrocarbons were formed as compared to carbonyl groups. This oxidation was also observed through the reduced crystalline property and cracked polyethylene surface using SEM. It was also observed that the product formed during the oxidation by the bio-surfactant could be solubilised into liquid media. For this rapid loss of oxidation product, a decrease in the mechanical properties of all the treated polyethylene samples was observed, and this deterioration was highest in the case of the pre-oxidised polyethylene incubated with the bio-surfactant for 2 months. In this study, a novel unique method for the biooxidation of polyethylene using a bio-surfactant was established.

Biodegradation of polyethylene via complete solubilization by the action of Pseudomonas fluorescens, biosurfactant produced by Bacillus licheniformis and anionic surfactant

“…Decrease in the crystallinity of polyethylene treated with 10% SDS, due to oxidation of both amorphous and crystalline region, was reported in previous work . Also, decrease in the crystallinity of biosurfactant‐treated polyethylene was observed in previous work . In the current study, polyethylene was treated with SDS, biosurfactant and incubated with P. fluorescens .…”

“…Increase in the amount of carbonyl and unsaturated hydrocarbon indicates oxidation of control polyethylene after treatment for 1 month with biosurfactant in PE 1.1, bacterial treatment of control polyethylene for 1 month with P. fluorescens in PE 3.1 and after treatment of control polyethylene with 10% SDS at 60 °C for 1 month in PE 5.1. Oxidation of control unoxidized polyethylene induced by biosurfactant and anionic surfactant has been observed in previous work . Hydrophobic ends of the amphiphilic biosurfactant, develop attachment with the surface of the polyethylene and hydrophilic ends of the biosurfactant protrude towards the aqueous solution.…”

“…As reported by Albertsson et al ., surfactant being an amphiphilic molecule reduces the hydrophobic nature of polyethylene and increases attachment of microbial species to the surface of the polyethylene . In our previous study, polyethylene was oxidized using biosurfactant produced by Bacillus licheniformis . In another study, hydrocarbon solubilization by anionic surfactant present during thermal oxidation of polyethylene was also observed …”

“…24 In our previous study, polyethylene was oxidized using biosurfactant produced by Bacillus licheniformis. 26 In another study, hydrocarbon solubilization by anionic surfactant present during thermal oxidation of polyethylene was also observed. 27 In the present work, to achieve a higher level of degradation of commercial polyethylene, it was treated with an anionic surfactant (SDS), a biosurfactant and incubated with P. fluorescens for bacterial conversion and consumption of oxidation products in different combinations.…”

“…Ester carbonyl index (ester CI), keto carbonyl index (keto CI) and double bond index (DBI) calculated from FTIR spectra of control polyethylene and treated polyethylene, are shown in the Fig. 1 26 Hydrophobic ends of the amphiphilic biosurfactant, develop attachment with the surface of the polyethylene and hydrophilic ends of the biosurfactant protrude towards the aqueous solution. Further, the availability of oxygen towards the polyethylene increases for this reason and polyethylene is oxidized.…”