Biodegradation of Degradable Plastic Polyethylene by Phanerochaete and Streptomyces Species

Abstract

The ability of lignin-degrading microorganisms to attack degradable plastics was investigated in pure shake flask culture studies. The degradable plastic used in this study was produced commercially by using the Archer-Daniels-Midland POLYCLEAN masterbatch and contained pro-oxidant and 6% starch. The known lignin-degrading bacteria Streptomyces viridosporus T7A, S. badius 252, and S. setonii 75Vi2 and fungus Phanerochaete chrysosporium were used. Pro-oxidant activity was accelerated by placing a sheet of plastic into a drying oven at 70°C under atmospheric pressure and air for 0, 4, 8, 12, 16, or 20 days. The effect of 2-, 4-, and 8-week longwave UV irradiation at 365 nm on plastic biodegradability was also investigated. For shake flask cultures, plastics were chemically disinfected and incubated-shaken at 125 rpm at 37°C in 0.6% yeast extract medium (pH 7.1) for Streptomyces spp. and at 30°C for the fungus in 3% malt extract medium (pH 4.5) for 4 weeks along with an uninoculated control for each treatment. Weight loss data were inconclusive because of cell mass accumulation. For almost every 70°C heat-treated film, the Streptomyces spp. demonstrated a further reduction in percent elongation and polyethylene molecular weight average when compared with the corresponding uninoculated control. Significant (P < 0.05) reductions were demonstrated for the 4and 8-day heat-treated films by all three bacteria. Heat-treated films incubated with P. chrysosporium consistently demonstrated higher percent elongation and molecular weight average than the corresponding uninoculated controls, but were lower than the corresponding zero controls (heat-treated films without 4-week incubation). The 2and 4-week UV-treated films showed the greatest biodegradation by all three bacteria. Virtually no degradation by the fungus was observed. To our knowledge, this is the first report demonstrating bacterial degradation of these oxidized polyethylenes in pure culture.

Effect of Starch Granule Size on Physical Properties of Starch‐Filled Polyethylene Film

“…Degradation of starch-filled polyethylene films has been reported by many researchers (Lee et al, 1991;Gould et al, 1990;Cole, 1990;Gage, 1990). Lee et al (1991) reported degradation of polyethylene molecules by lignindegrading bacteria in those films containing starch and prooxidant. Because of its hydrophilic properties, starch incorporation may, however, introduce undesirable properties into polyethylene film.…”

“…Starch incorporation produces a plastic film with a porous structure, which enhances the accessibility of the plastic molecules to oxygen and microorganisms (Griffin, 1974). Degradation of starch-filled polyethylene films has been reported by many researchers (Lee et al, 1991;Gould et al, 1990;Cole, 1990;Gage, 1990). Lee et al (1991) reported degradation of polyethylene molecules by lignindegrading bacteria in those films containing starch and prooxidant.…”

Potential for Bioremediation of Xenobiotic Compounds by the White‐Rot Fungus Phanerochaete chrysosporium

“…Production of lignin peroxidases and Mn(I1) peroxidases was observed during these experiments (Milstein et al, 1992). Polyethylene containing 6% starch was incubated with P. chrysosporium in another study (Lee et al, 1991). The fungus did not degrade polyethylene, but this may have been due to the high nitrogen content of the medium used, which is known to inhibit the ligninolytic system of most whiterot fungi.…”

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

“…Thermal oxidation of polyethylene is mainly carried out at temperatures ranging from 45 ∘ C to 150 ∘ C and generally characterized by lower temperatures with the longer time periods and higher temperatures with the shorter time periods. [3][4][5] For photo-oxidation, irradiation of polyethylene by UV is generally carried out at a temperature above 50 ∘ C. [6][7][8] The rate of polyethylene accumulation in nature is increasing each and every year and under this situation, faster and more effective methods of polyethylene removal must be found. Research has been carried out to increase the rate of biodegradation by increasing the extent of polyethylene oxidation and by using effective microbial species for polyethylene biodegradation.…”