Oxidative biodegradation of single-walled carbon nanotubes by partially purified lignin peroxidase from Sparassis latifolia mushroom Gayathri Chandrasekaran a , Soo-Kyung Choi a , Young-Chul Lee b , Geun-Joong Kim c , Hyun-Jae Shin a, * a Department of Chemical and Biochemical Engineering, Chosun University, Gwangju 501-759, Republic of Korea b Department of Biological Engineering, College of Engineering, Inha University, Incheon 402-751, Republic of Korea c Department of Biological Science, College of Natural Sciences, Chonnam National University, Gwangju 500-757, Republic of Korea 1. Introduction Carbon-based nanotechnology has become one of the most important and exciting aspects of research in various fields and especially in engineering and biology [1–6]. Presently, the environmental and human health concerns over engineered nanomaterials (ENMs), especially on single-walled carbon nano- tubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), are increasing [7–10], an important issue to be taken into consideration. Moreover, it was stated that carbon nanotubes (CNTs) affect the environment as much as they affect humans [11– 13], and the levels of risk are proportional to the amount of ENMs produced globally. Various reports have stated that the CNTs cause skin cancer, oxidative stress, granuloma formation, fibrosis, lung cancer, genotoxicity, and mutagenicity [12]. Moreover, the dermal toxicity of the SWCNTs causes oxidative stress to the skin. Various types of CNT products, including raw grade and thermally-treated grades, are available; they contain iron, nickel, and yttrium, which exhibited a proven pulmonary toxicity [9,12]. Although they contain lower amounts of catalysts, the overall research has revealed that CNTs tend to cause epithelioid granulomas and interstitial inflammation in animals [14]. Recently, it has been demonstrated that CNTs can trigger some biological responses similar to those of asbestos. For example, MWCNTs (less than 20 mm) are short and soft, which could cause serious health problems with the identical mechanism [15]. As a result, such functionalized CNTs to reduce toxicity and grant biocompatible and biodegradable characteristics have been developed [16]. However, it is still stressed that the disposal of CNTs is critical issues. Concerning the environmental hazards of CNTs, those trials are reported that SWCNTs and MWCNTs could be degraded by enzyme-catalyzed oxidations within a few weeks or months [17]. Among several peroxidases which are activated by H 2 O 2 to generate unstable radicals for degradation of carbonaceous nanomaterials, white-rot fungi (WRF) can degrade a wide range Journal of Industrial and Engineering Chemistry xxx (2013) xxx–xxx A R T I C L E I N F O Article history: Received 10 September 2013 Accepted 8 December 2013 Available online xxx Keywords: Single-walled carbon nanotubes Lignin peroxidase Sparassis latifolia Biodegradation Bioremediation A B S T R A C T Two types of carbon nanotubes (usually single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs)) have been intensively focused on academic researches and mass- produced for wide applications such as composite materials, biosensors, and drug delivery systems. However, due to oxidative stress-dependent and physically-induced cellular toxicity of CNTs, many efforts to render biocompatible and biodegradable properties in CNTs have been highlighted. Thus, taking into the consideration of exposure in human health and the environment, biodegradation of CNTs as a potential disposal is highly addressed. In this study, lignin peroxidase (LiP) was isolated and partially purified from the fruiting bodies of the edible mushroom Sparassis latifolia (S. latifolia). The biodegradation of raw grade and thermally-treated carboxylated SWCNTs (denoted as ASA and AST) with this enzyme was investigated, prior to more biodegradation-resistant MWCNTs. The interactions between the SWCNTs and LiP were investigated using various techniques, and the intermediate by- products of the LiP degradation were identified. Our findings demonstrated that both ASA and AST were efficiently degraded by LiP where the producing radicals by the LiP played a critical role in the biodegradation of SWCNTs. The final degraded products were confirmed with the generation of CO 2 gas. Conclusively, the low extraction cost of partially purified enzyme from mushrooms can make this approach a promising alternative in environmental bioremediation as a practical application. ß 2013 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry. * Corresponding author. Tel.: +82 62 2307518; fax: +82 62 2307226. E-mail address: shinhj@chosun.ac.kr (H.-J. Shin). G Model JIEC-1752; No. of Pages 8 Please cite this article in press as: G. Chandrasekaran, et al., J. Ind. Eng. Chem. (2013), http://dx.doi.org/10.1016/j.jiec.2013.12.022 Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jiec 1226-086X/$ – see front matter ß 2013 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry. http://dx.doi.org/10.1016/j.jiec.2013.12.022