Degradation of unpretreated and thermally pretreated polypropylene by soil consortia

Unpretreated (PP-UT) and thermally pretreated (at 80 οC for 10 days) polypropylene (PP-TT) films of 0.05 mm thickness were subjected to in vitro biodegradation in minimal medium with mixed soil culture for 12 months. In this period 10.7 and 0.4% weight loss was observed with PP-TT and PP-UT, respectively. The tensile strength decreased by 51.8 and 28.3%, the crystallinity increased by 28 and 33% and isotacticity increased by 3 and 9%, respectively, over the same time period. The ester carbonyl index in PP-TT increased up to 9 months and later decreased indicating abiotic followed by biotic process. No such changes were observed with PP-UT. Methyl group index decreased in both the cases indicating oxidation at the primary carbon. Increase in surface energy indicated that the polymer became hydrophilic. Surface changes were observed by SEM and AFM. A single culture was isolated at the end of 12 months and it was identified as Bacillus flexus. The morphology of the organism was rods in a chain and it was present in the form of an endospore

Growth of Pseudomonas and Bacillus biofilms on pretreated polypropylene surface

Unpretreated and Aquaregia, Fenton, thermal and short UV pretreated polypropylene films of 0.05 mm thickness were subjected to biodegradation in vitro in minimal medium with four soil cultures, namely Pseudomonas azotoformans, Pseudomonas stutzeri, Bacillus subtilis and Bacillus flexus separately for 12 months. P. azotoformans and B. subtilis are relatively hydrophobic, produce biosurfactant and form biofilm on the polymer with comparatively higher carbohydrate and protein than the other two organisms. All the organisms make use of the polymer as their carbon source. Highest weight loss (2.5%) was observed in the case of short UV treated polymer exposed to B. flexus after one year. The carbonyl indices decreased in one year in the case of pretreated polymer and increased in the case of untreated polymer, indicating only abiotic oxidation in the absence of pretreatment. Increase in surface energy indicated that the polymer became more hydrophilic when compared to the original. P. stutzeri had marginal effect on the polymer

Biodegradation of polyethylene and polypropylene

9-22Polyethylene and polypropylene are the two polyolefins with wide ranging applications. They are recalcitrant and hence remain inert to degradation and deterioration leading to their accumulation in the environment, and, therefore creating serious environmental problems. In this review, biodegradation of these two polymers under in vitro conditions is reported. An attempt has been made to cover the mechanism of biodegradation, the various bacterial and fungal organisms that have been reported for the same, methods adopted for the studies and different characterization techniques followed to measure the extent of degradatio