Korea Institute of Industrial Technology

The widespread use of plastics has created a significant environmental challenge due to the accumulation of plastic waste. In this study, we isolated a bacterial strain, named JJY06, from rice field soil in the Republic of Korea. Based on 16S rRNA gene sequencing, the strain was identified as an Aeromicrobium species, showing 99.93 % similarity to Aeromicrobium tamlense SSW1-57. JJY06 demonstrated the ability to degrade several commercial bio-plastics, including poly(ε-caprolactone) (PCL), polybutylene succinate (PBS), and poly(butylene adipate-co-terephthalate) (PBAT), even at low temperatures (10 °C). After 25 days, JJY06 achieved 100 % degradation of PCL, while after 40 days, it degraded 38.6 % of PBS and 33.5 % of PBAT. When tested at 25 °C, the degradation rates increased significantly, with complete degradation of PCL occurring within 8 days, and degradation of PBS and PBAT reaching 55.6 %, respectively, within 21 days. Interestingly, the strain formed clear zones on agar plates emulsified with PCL, PBS, and PBAT at 4 °C after one month of incubation. The degradation was confirmed by SEM and GPC analyses. Genome sequencing revealed that JJY06 has genome size of 4.52 Mb, containing 4076 protein-coding genes. Cold-shock proteins and plastic-degradation-related gene clusters suggests their adaptation to low temperatures and biodegradation potential. RAST annotation also identified genes associated with antibiotic and heavy metal resistance, suggesting adaptive mechanisms for survival in harsh environments. This study highlights Aeromicrobium sp. JJY06 as a promising candidate for degrading bio-plastics in cold environments.

The shift towards sustainable alternatives to petroleum-based polymers has become essential for addressing environmental challenges. Among these alternatives, bio-plastics such as poly(3-hydroxybutyrate) (PHB) have gained considerable attention due to their biodegradability into water and carbon dioxide through microbial activity. PHB is one of the most widely commercialized bio-plastics. However, its excessive accumulation in the environment due to insufficient degradation remains a significant ecological concern. This study focused on isolating and characterizing PHB-degrading bacteria from soil samples collected from rice fields. Screening led to the identification of five PHB-degrading bacterial strains belonging to different genera. Among these, Streptomyces sp. AG7 and Streptomyces sp. RG41 were identified as the most effective PHB degraders. Their PHB-degrading abilities were evaluated in shake-flask cultures using PHB films as substrates. After 20 days of incubation at 37 °C, Streptomyces sp. AG7 and Streptomyces sp. RG41 achieved PHB degradation rates of approximately 74.7 % and 68.5 %, respectively. Additionally, both strains demonstrated the ability to produce indole-3-acetic acid (IAA), a key phytohormone that promotes plant growth, and exhibited phosphate-solubilizing activity, which enhances nutrient availability. Further analysis using scanning electron microscopy (SEM) revealed structural changes in the PHB films, while gel permeation chromatography (GPC) confirmed significant alterations in the polymer's molecular properties. These findings highlight the potential of utilizing soil-derived Streptomyces species for sustainable PHB waste management, in order to promote plant growth, improve soil fertility through phosphate solubilization, and contribute to agricultural sustainability.

Artificial vascular grafts, as blood vessel substitutes, are a prime challenge in tissue engineering and biomaterial research. An ideal artificial graft must have physiological and mechanical properties similar to those of a natural blood vessel, and hemocompatibility on its surface. We designed and fabricated artificial grafts by applying 3D printing and templated technology, which is endowed with morphologically patient-specific vascular reconstruction. To optimize mechanical properties, the graft wall was engineered with a controllable hybrid porous structure through a multilayer combination of porous and nonporous coatings, thereby achieving biomimetic mechanical flexibility with reduced stiffness. Further, we successfully synthesized dopamine-conjugated heparin (Hep-DA) utilizing carbodiimide chemistry, and coated it on a 3D porous graft to improve both surface adhesion and anticoagulant ability. The Hep-DA-coated 3D graft did not show significant cytotoxic effects with a long-term sustained heparin release. We performed a preclinical study in swine using the developed graft along with commercially available graft ePTFE and Dacron as a reference. They were implanted in the swine aorta for 28 days and the implanted grafts were harvested for further analysis. Histopathology study results showed the feasibility of the developed artificial vascular grafts that have less calcification, fibrosis, and collagen deposition than commercially available grafts.