Degradation of Poly(ε-caprolactone) by a Thermophilic Community and Brevibacillus thermoruber Strain 7 Isolated from Bulgarian Hot Spring.

Nikolina Atanasova,Stoyanka Stoitsova,Ivanka Boyadzhieva,Nadja Radchenkova,Kaloyan Petrov,Margarita Kambourova,Tsvetelina Paunova-Krasteva

doi:10.3390/biom11101488

Nikolina Atanasova, Stoyanka Stoitsova + Show 5 more

Open Access

https://doi.org/10.3390/biom11101488

Copy DOI

Abstract

The continual plastic accumulation in the environment and the hazardous consequences determine the interest in thermophiles as possible effective plastic degraders, due to their unique metabolic mechanisms and change of plastic properties at elevated temperatures. PCL is one of major biodegradable plastics with promising application to replace existing non-biodegradable polymers. Metagenomic analysis of the phylogenetic diversity in plastic contaminated area of Marikostinovo hot spring, Bulgaria revealed a higher number taxonomic groups (11) in the sample enriched without plastic (Marikostinovo community, control sample, MKC-C) than in that enriched in the presence of poly-ε-caprolactone (PCL) (MKC-P), (7). A strong domination of the phylum Proteobacteria was observed for MKC-C, while the dominant phyla in MKC-P were Deinococcus-Thermus and Firmicutes. Among the strains isolated from MKC-P, the highest esterase activity was registered for Brevibacillus thermoruber strain 7 at 55 °C. Its co-cultivation with another isolate resulted in ~10% increase in enzyme activity. During a 28-day biodegradation process, a decrease in PCL molecular weight and weight loss were established resulting in 100% degradation by MKC-P and 63.6% by strain 7. PCL degradation intermediate profiles for MKC-P and pure strain were similar. Broken plastic pieces from PCL surface and formation of a biofilm by MKC-P were observed by SEM, while the pure strain caused significant deformation of PCL probes without biofilm formation.

Highlights

Plastic’s invasive entrance in human life notably improved its standard, making it easier, safer, and more colorful
We report an effective PCL degradation at 55 ◦ C by a microbial community from the Marikostinovo hot spring (MKC), Bulgaria and an isolation of Brevibacillus thermoruber strain 7 with an esterase activity
Metagenomic analysis revealed that the community composition in the control that did not contain plastic (MKC-C) (Table 1 and Figure 1A) was characterized by a higher diversity

Summary

Introduction

Plastic’s invasive entrance in human life notably improved its standard, making it easier, safer, and more colorful Due to their exclusive properties, such as bio-inertia, resistance to environmental influence and microbial action, easy manufacturing, light weight, and low production cost, everyday plastic use shows an exponentially increasing trend for production and consumption. Synthetic plastics are widely used in the global economy, with an annual worldwide production at a scale of 350 to 400 million metric tons [1]. Due to their nature of solid and densely cross-linked polymers, they are not accessible for microbes and enzymes. Among other economies around the world, the COVID-19 pandemic has impacted the functioning of the global polycaprolactone market space [3]

Methods

Results

Discussion

Conclusion