Composting of oiled bleaching earth: Fatty acids degradation, phytotoxicity and mutagenicity changes Agnieszka Piotrowska-Cyplik a, * , qukasz Chrzanowski b , Pawe1 Cyplik c , Jacek Dach d , Anna Olejnik c , Justyna Staninska c , Jakub Czarny e , Andrzej Lewicki d , Roman Marecik c , Jolanta Powierska-Czarny f a Institute of Food Technology of Plant Origin, Pozna n University of Life Sciences, Wojska Polskiego 31, 60-624 Pozna n, Poland b Institute of Chemical Technology and Engineering, Pozna n University of Technology, Pl. M. Sklodowskiej-Curie 2, 60-965 Pozna n, Poland c Department of Biotechnology and Food Microbiology, Pozna n University of Life Sciences, Wojska Polskiego 48, 60-627 Pozna n, Poland d Institute of Agricultural Engineering, Pozna n University of Life Sciences, Wojska Polskiego 50, 60-625 Pozna n, Poland e BioMarkers, Sielska 17A, 60-129 Pozna n, Poland f Institute of Forensic Genetics, Al. Mickiewicza 3/4, 85-071 Bydgoszcz, Poland article info Article history: Received 22 May 2012 Received in revised form 20 November 2012 Accepted 11 December 2012 Available online 7 February 2013 Keywords: Composting Fatty acids biodegradation Oiled bleaching earth abstract Due to high fat content the treatment of oiled bleaching earth is very challenging. The neutralization of such waste may be carried out by employing the composting process. In this study, the efficiency of the composting process conducted with 19% addition of commercial oiled bleaching earth to waste sludge was evaluated. Maize straw was used as a structural material. The activity of lipases and dehydrogenases was measured during the biodegradation process. As a result of composting, changes in C/N ratio occurred (from 31 to 15) and the efficiency of fatty acids biodegradation reached 95%. The composting process also resulted in the removal of the initial phytotoxicity of composts. The mature compost did not exhibit any form of phytotoxicity during assays with Phytotoxkit. The Ames test excluded mutagenicity of any components in the compost. These results suggest that the proposed composting method may potentially be employed for rapid and efficient remediation of industrial waste containing oiled bleaching earth and waste sludge. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The production and processing of edible oils and fats is among many branches of food industry, which produce challenging wastes in terms of biodegradability (Arvanitoyannis and Kassaveti, 2007; Chandra and Sathiavelu, 2009). The waste fats are collected after cleaning refining devices, hardening of fats, and other technological operations. Such wastes commonly consist of fatty acids after refining, oil slime, autoclave oil, and oiled bleaching earth (which contains 10e60% fatty substances, depending on the technology used). About 40000 tons of oiled bleaching earth is generated by fat production plants each year in Poland alone and it is expected that the quantity may increase in the following years (Piotrowska- Cyplik et al., 2012). Land disposal of oiled bleaching earth is usually not preferred in agriculture. Generally, a negative influence on the physico-chemical properties of soil and, in consequence, on the growth and development of plants can be observed if the content of oiled bleaching earth in the soil mass exceeds 3% (Wierzba et al., 2000). The application of the microbiological composting process is among the most rational utilization methods for the residues rich in oils and fats (Michailides et al., 2011; Tortosa et al., 2012). Recent experiments confirmed the usefulness of composting for the utilization of residues rich in oils and fats, fat sludges or post-filtration fatty acids (Altieri et al., 2011; Maliki and Lai, 2011). However, this strategy requires improving the unfavor- able conditions, which are inevitably associated with fatty substances, as well as determining the crucial factors associated with the efficiency of fat degrading microorganisms (Toledo et al., 2006). The addition of a structural material may enhance the physical properties of the waste. This contributes to better main- tenance of aerobic conditions, which result in increased removal efficiency (Klauss and Papadimitrou, 2002; Kulcu and Yaldiz, 2007). The objective of the presented studies was to investigate the course of biodegradation of fatty acids in waste products (oiled bleaching earth and sewage sludge) obtained after refining of plant oils and sewage sludge treatment, during the composting process. In order to achieve the desirable process efficiency, it is essential to improve the physical properties of the sludge by the inclusion of * Corresponding author. Tel.: þ48 61 8487284; fax: þ48 61 8487314. E-mail address: apio@up.poznan.pl (A. Piotrowska-Cyplik). Contents lists available at SciVerse ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod 0964-8305/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ibiod.2012.12.007 International Biodeterioration & Biodegradation 78 (2013) 49e57