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

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.

Ɛ-Polycaprolactone degradation by a thermostable lipase isolated from Brevibacillus thermoruber strain 7

“…SEM analysis revealed deep changes in the PCL pearl surface after a week. Similar deep destroyed PCL surface has been observed during the growth of the strain 7 in a medium with PCL as the only carbon source(Atanasova et al 2021a). Visible changes on PCL surface have been seen after longer cultivation of some strains in PCL containing medium − 14 days cultivation of Bacillus subtilis at 30°C(Balkova et al 2014), 20 days cultivation at 40°C of Bacillus sp (Motiwalla et al 2013…”

“…B. thermoruber strain 7, active on -polycaprolactone was isolated from a hot spring Marikostinovo, located in South-West Bulgaria (41.4314_ N, 23.3335 E) with water temperature of 55°C and pH of 7.8 (Atanasova et al 2021a).…”

“…Several decades ago synthetic polymers with long molecules, named plastics were introduced as substitutes of natural materials and since then they entered invasively in almost every area of industry and social human life making it more colorful, easier, and safer (Atanasova et al 2021a). Despite of the undoubted impact of plastics in erasing the human life standard the exponential accumulation of their non-degradable products in the environment represents growing concern for wild life and provokes an enormous interest in searching of degradable products or new alternatives for the reduction of waste.…”

“…In our previous work an evidence for an effective PCL degradation by a thermophilic bacterium Brevibacillus thermoruber strain 7 and the community from which the strain was isolated was provided (Atanasova et al 2021a). In the present paper we report on the isolation of a lipase from this strain, its puri cation, characteristics of the puri ed enzyme, the identi cation of the degradation products, and changes of PCL surface by the enzyme.…”

A Thermostable Lipase Isolated from Brevibacillus thermoruber Strain 7 Degrades Ɛ-Polycaprolactone

“…Several decades ago, synthetic polymers with long molecules, named plastics, were introduced as substitutes for natural materials and since then they have invasively entered almost every area of industry and social life by making them more colorful, easier, and safer [ 1 ]. Despite the undoubted impact of plastics in erasing the human life standard, the exponential accumulation of their non-degradable products in the environment represents a growing concern for wildlife and provokes enormous interest in searching for degradable products, or new alternatives to reduce waste.…”