Contents lists available at ScienceDirect Biocatalysis and Agricultural Biotechnology journal homepage: www.elsevier.com/locate/bab Effects of the methane-inhibitors Nitrophenol, 5-Nitrobenzimidazol and two new synthetic nitrocompounds on in vitro ruminal fermentation Asma Kheddouma a,b, ⁎ , Rabah Arhab b , Antonio Ignacio Martín-García c , Laiche Aouidane a , Abdelmalek Bouraiou d a University of Abbes Laghrour Khenchela, Faculty of Nature and Life Sciences, BP: 1252 Route de Batna Khenchela, Algeria b Département des Sciences de la Nature et de la Vie, Université Larbi Ben M′Hidi, Oum El Bouaghi, Algeria c Estación Experimental del Zaidín (CSIC), Camino del Jueves s/n, 18100 Armilla, Granada, Spain d Unité de Recherche de Chimie de l′Environnement et Moléculaire Structurale (CHEMS), Université-Constantine 1 (ex Mentouri-Constantine), Algeria ARTICLE INFO Keywords: Methane-inhibitor Rumen Nitrophenol 5-Nitrobenzimidazol ABLE 244 ABLE 245 ABSTRACT The objective of this study was to examine the effects of four nitrocompounds (Nitrophenol, 5-Nitrobenzimidazol and two synthetic nitrocompounds ABLE 244 and ABLE 245) on methane production and fermentation char- acteristics using in vitro rumen batch culture. 0, 2, 8 or 12 μM of each nitrocompound were incubated. The higher concentrations of Nitrophenol and 5-Nitrobenzimidazol produced 60% less CH 4 (P < 0.05) compared to con- trols, while two synthetic nitrocompounds ABLE 244 and ABLE 245 had no effect on CH 4 production. Quantification of fermentation end-products indicated that fermentation efficiencies were not compromised by the nitro-treatments. 1. Introduction Methane is a greenhouse gas that contributes to global warming (Lassey, 2007). After carbon dioxide; methane is considered the most potent greenhouse gas (IPCC et al., 2001), due to the higher efficiency (20–30 times) of long-wave radiation absorption relative to CO 2 and involvement of CH 4 in chemical reactions that give ozone as the final product (Crutzen, 1995). Due to the increased concentration of CH 4 in the atmosphere in the post-industrial era, several investigations have been involved to identify sources and sinks of methane and to estimate their effects (Bodelier Paul and Laanbroek, 2004; Hilary et al., 2012; Guangming et al., 2013). In the livestock sector, ruminants contribute significantly to global greenhouse gas emissions (Yáñez-Ruiz and Martín-García, 2016). In terms of the environment, ruminal methanogenesis accounts for about 12–14% of total greenhouse gas emissions (Zervas and Tsiplakou, 2012). But methane production results in a loss of raw energy (4–12%) for cattle fed on forage and fodder (Zhenming et al., 2012). In the rumen, CH 4 is produced by methanogens catalyzing the transfer of hydrogen and carbon dioxide into methane. In addition to methane production, the low hydrogen partial pressure by methanogenesis has a great influence on other products of the non-methanogenic and fer- mentative microbial community (Wolin et al., 1997). In many cases, the reduction of CH 4 production in the rumen may thus affect digestive function and microbial cell yields due to altered fermentation effi- ciencies associated with microbial hydrogen transfer reactions (Miller, 1995; Van Nevel and Demeyer, 1996; Anderson et al., 2008) Several methods have been developed by ruminant microbiologists to reduce the energy losses associated with the production of ruminal CH 4 (Anderson et al., 2008), and many chemical inhibitors reduce methanogenesis (eg monensin and lasalocide) (Russell and Strobel, 1989), plant extracts (tannins for example) (Hariadi and Santoso, 2010) or new synthetic compounds (Patra et al., 2017). These strategies in- volve supplementing ruminants with anti-methanogenic compounds that directly inhibit methanogens or inhibit the biochemical reactions involved in methane production (Bozic et al., 2009). Among these methods; is the change in electron acceptors that consume more effi- ciently the reducing equivalents produced during fermentation to re- direct the electron flux from the reduction of carbon dioxide to CH 4 (Anderson and Rasmussen, 1998; Sar et al., 2005). Several ni- trocompounds have the ability to reduce ruminal methane in vitro up to 90% (Anderson et al., 2003), such as nitroethane, 2-nitroethanol, 2- nitro-1-propanol and 3- nitro-1-propionic inhibit the rumen. CH 4 pro- duction (Anderson and Rasmussen, 1998; Anderson et al., 2003, 2008; Bozic et al., 2009; Gutierrez-Banuelos et al., 2008). In addition, ni- troethane and 2-nitro-1-propanol reduce CH 4 -producing activity in vivo (Anderson et al., 2006; Gutierrez-Banuelos et al., 2008; Zhang and Yang, 2011), as well as ethyl-3. -nitrooxy propionate and 3- https://doi.org/10.1016/j.bcab.2018.03.004 Received 5 January 2018; Received in revised form 19 February 2018; Accepted 7 March 2018 ⁎ Corresponding author at: University of Abbes Laghrour Khenchela, Faculty of Nature and Life Sciences, BP: 1252 Route de Batna Khenchela, Algeria E-mail address: kheddouma.asma@hotmail.fr (A. Kheddouma). Biocatalysis and Agricultural Biotechnology 14 (2018) 160–165 Available online 11 March 2018 1878-8181/ © 2018 Published by Elsevier Ltd. T