# Microbial Depolymerization of Epoxy Resins: A Novel Approach to a Complex Challenge
###### Abstract  
The objective of this project is evaluating the potential of microbes (fungi and bacteria) for the depolymerization of epoxy, aiming at the development of a circular management of natural resources for epoxy in a long-term prospective. For depolymerization, epoxy samples were incubated for 1, 3, 6 and 9 months in soil microcosms inoculated with _Ganderman albersum_. Contact angle data revealed a reduction in the hydrophobicity induced by the fungus. Environmental scanning electron microscopy on epoxy samples incubated for more than 3 years in microbiological water revealed abundant microbiota. This comprised microbes of different sizes and shapes. The fungi _Trichoderma harzianum_ and _Aspectillus calidostusus_, as well as the bacteria _Variororax_ sp. and _Methylolversatilis discipulorum_, were isolated from this environment. Altogether, these results suggest that microbes are able to colonize epoxy surfaces and, most probably, also partially depolymerize them. This could open promising opportunities for the study of new metabolisms potentially able depolymerize epoxy materials. epoxy resin; microbial depolymerization; recycling; _Ganderman adgersum; Methylolversatilis discipulorum_202212466202202120220220220220220220220220220220220220220220220220220220220220220220222022022022202202202220220222022202220222022202220222022202222022220222220222222222222222222222222222222222222222222222222222222 engineering, for the strengthening of existing structures, cars (BMW 3), freight vehicles and wind power rotor blades [3; 4]. Current estimations predict an increasing demand for carbon fibers in the future [5; 6]. This might result in a possible supply gap in the short-mid-term future [7]. Strategies considered for recycling continuous carbon fibers from CFRP epoxy composites are thermal (pyrolysis) and chemical (solovlysis) methods. However, the high temperature and the aggressive chemicals employed in these approaches cause significant degradation of the carbon fibers as well. Some of these treatments yield discontinuous rather than continuous fibers [8; 9], limiting their potential to be recycled [10; 11]. Another drawback is the large amount of energy required for pyrolysis and the large amount of chemicals required for solvolysis, which will lead to undesirable emissions or residual waste that has to be safely disposed of [12]. Hence, an efficient recycling method for the recovery of carbon fibers currently does not exist. Increasing future use, finite service lifetimes of CFRP components and structures and more stringent regulations will demand safe and environmentally friendly recycling technologies. Therefore, such efficient methods at affordable costs are essential for sustainable use of CFRP epoxy composites. The study of microbial metabolisms has great potential for developing more sustainable processes, allowing a decrease in the human ecological footprint and preservation of precious natural resources. Recent research on thermoplastic material presents an encouraging and successful example for moving towards a more circular and green economy. An enzymatic degradation of polyethylene terephthalate (PET), followed by exploitation of the depolymerization products by bacteria to obtain two new biodegradable biopolymers (polyhydroxyalkanoate (PHA) and poly(amide urethane)) was proposed [13]. However, microbial degradation of epoxy resins and CFRP epoxy composites is still largely unexplored. There is scant literature on the subject, and that which is available is mostly focused on the potentially detrimental effect of microbes on CFRP composites [14; 15; 16]. Electrochemical impedance spectroscopy (EIS) was used to assess the microbial degradation of a protective epoxy coating on a carbon steel material [17]. Samples incubated in sea water with the bacterium _Pseudomonas putida_ revealed decreasing protective performance of this coating upon microbial colonization.