Anaerobic Toxicity Assay of Polychlorinated Biphenyl: Focus on Fermentative-Methanogenic Community M. R. de Lima e Silva & F. Motteran & I. K. Sakamoto & M. B. A. Varesche Received: 30 March 2016 /Accepted: 28 July 2016 /Published online: 9 August 2016 # Springer International Publishing Switzerland 2016 Abstract This study aims to evaluate extensively the inhibition of six PCB (polychlorinated biphenyls) con- geners in batch reactors under fermentative- methanogenic condition. The reactors with anaerobic sludge were fed with mineral medium, co-substrates (ethanol and sodium formate), and five PCB concentra- tions. The maximum methane production (MMP) in the reactor without PCB (RC), with 0.5 (R0.5), 1.5 (R1.5), 3.0 (R3.0), 4.5 (R4.5), and 6.0 mg/L (R6.0) of PCB, was 654.83, 193.08, 111.65, 104.60, 96.67, and 79.50 μmolCH 4 /gTVS, respectively. The methane inhi- bition for the reactors R0.5, R1.5, R3.0, R4.5, and R6.0 were 70, 83, 84, 85, and 88 %, respectively. The con- centration that causes 50 % of inhibition (IC 50 ) for PCB was 0.03 mg/L. The inhibition results present two dif- ferent profiles according to the concentration range. The concentration range of 0.5 to 3.0 mg/L of PCB inhibited the acetoclastic microorganisms and the concentration of 4.5 to 6.0 mg/L inhibited both methanogenic and acidogenic population. The acidogenic populations were less sensitive to the PCB than the methanogenic. Lower methane production and organic matter removal were verified in all reactors with PCB compared to RC, without PCB. The microbial community highlighted lower diversity index for reactors with higher PCB concentration. In the reactors with PCB, the populations of bacteria domain were more susceptible to composi- tion changes than the archaea domain. The inhibitory effect of PCB is concentration-dependent and affected differently the populations of organisms in the reactor. Moreover, the range of 4.5 to 6.0 mg/L of PCB severely inhibited the anaerobic community. Keywords Inhibitory effect . Co-substrate . PCR/ DGGE . PCB . Acidogenicbacteria . Methaneproduction 1 Introduction The polychlorinated biphenyls (PCB) constitute a group of compounds worldwide used due its stable organic molecules with low flammability and good insulating property. These characteristics led to their use in trans- formers, capacitors, and dielectrics as thermal insulating fluids (Abramowicz 1990; Tiedje et al. 1993; Borja et al. 2005). These compounds were extensively produced until the confirmation of their toxicity and adverse health effects that resulted in the banishment of their manufacture in many countries (ATSDR, 2000). Despite the prohibition of its production, the envi- ronmental PCB contamination was evidenced in recent papers demonstrating that the contamination of animals and human is still a current risk, revealing the necessity of management and elimination of these toxic com- pounds (Gonzalez-Mille et al. 2013a; Gonzalez-Mille Water Air Soil Pollut (2016) 227: 316 DOI 10.1007/s11270-016-3016-7 M. R. de Lima e Silva : F. Motteran : I. K. Sakamoto : M. B. A. Varesche (*) Department of Hydraulics and Sanitation, School of Engineering of São Carlos, University of São Paulo, Av. Trabalhador Sãocarlense, 400, 13566-590 São Carlos, São Paulo, Brazil e-mail: varesche@sc.usp.br M. R. de Lima e Silva e-mail: mrubia.limasilva@gmail.com