ASSESSING THE BIOTECHNOLOGICAL INFLUENCE OF ENVIRONMENTAL STRESSORS ON SYNERGISTIC MICROBIAL PLASTIC WASTE DEGRADATION

Abstract

Background: Plastic pollution is a critical environmental issue due to the persistence of synthetic polymers in natural ecosystems. Conventional waste management approaches are inefficient in addressing this challenge, necessitating sustainable alternatives. Microbial degradation has emerged as a promising biotechnological solution, as specific bacterial and fungal strains possess enzymatic capabilities to degrade plastics. However, the efficiency of microbial plastic biodegradation is highly dependent on environmental factors, including temperature, pH, and oxygen availability. This study evaluates how these stressors influence the degradation of polyethylene (PE) and polyethylene terephthalate (PET) to optimize microbial plastic waste management strategies.

Objective: This study aimed to assess the impact of temperature, pH, and oxygen availability on microbial plastic degradation efficiency and to determine the optimal environmental conditions that enhance biodegradation rates.

Methods: Following ethical approval (ERC144/23) from Punjab University Lahore, plastic-degrading microbial strains were isolated from landfill sites and aquatic environments. These isolates were cultured in a controlled laboratory setting using minimal salt medium supplemented with PE and PET as the sole carbon sources. The experiment was conducted over four weeks, with plastic samples incubated at 25°C, 35°C, and 45°C under pH conditions of 5, 7, and 9. Oxygen availability was controlled to create aerobic and anaerobic conditions. Plastic degradation efficiency was assessed by weight loss measurements, surface morphology analysis via scanning electron microscopy, and microbial growth monitoring through optical density (OD600) measurements. Statistical analyses were performed using one-way ANOVA and t-tests, with p-values < 0.05 considered significant.

Results: Microbial degradation efficiency was significantly influenced by environmental stressors (p < 0.05). The highest degradation rates were observed at 35°C and pH 7, with PE and PET weight loss reaching 8.5 ± 0.5% and 7.0 ± 0.4%, respectively. Lower degradation occurred at 25°C (4.2 ± 0.3% for PE, 2.8 ± 0.2% for PET) and 45°C (3.1 ± 0.2% for PE, 1.9 ± 0.2% for PET). Similarly, microbial activity was highest at pH 7 (OD600 = 1.41 ± 0.07) and declined under acidic (pH 5) and alkaline (pH 9) conditions. Oxygen availability significantly affected degradation rates, with aerobic conditions yielding 10.1 ± 0.6% PE degradation and 7.8 ± 0.5% PET degradation, whereas anaerobic conditions resulted in markedly lower values (3.8 ± 0.3% for PE, 2.5 ± 0.2% for PET) (p < 0.05).

Conclusion: This study confirms that temperature, pH, and oxygen availability significantly impact microbial plastic degradation. Optimal conditions of 35°C, pH 7, and aerobic environments yielded the highest degradation efficiency. These findings support the development of biotechnological strategies to enhance microbial plastic biodegradation, contributing to sustainable waste management solutions.