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.