Liquid chromatography/high resolution tandem mass spectrometry e Tool for the study of polyphenol profile changes during micro-scale biogas digestion of grape marcs Luk  a  s Ku  cera, Ond  rej Kurka, Petr Bart  ak, Petr Bedn  a  r * Regional Centre of Advanced Technologies and Materials, Department of Analytical Chemistry, Faculty of Science, Palacký University,17. listopadu 12, 779 00, Olomouc, Czech Republic highlights  Optimization of anaerobic fermentation of wine waste material in micro-scale.  Evaluation of differences in gasification of wine waste and commonly used materials.  Study of the fate of flavonoids during gasification in complex waste mixture. article info Article history: Received 11 July 2016 Received in revised form 22 September 2016 Accepted 26 September 2016 Available online 3 October 2016 Handling Editor: Y Liu Keywords: Anaerobic digestion Chromatography Mass spectrometry Polyphenols Wine grape marcs abstract A microscale discontinuous fermenter was used for anaerobic digestion of wine waste e a hardly gas- ifiable feedstock material. Efficiency of biogas production, i.e. changes in content of nitrogen, oxygen, carbon dioxide and methane in gas phase, was monitored by gas chromatography/mass spectrometry. Liquid chromatography/high resolution tandem mass spectrometry in combination with principal component analysis and orthogonal projection to latent structures was used to reveal main chemical differences of gasified wine waste mixture from commonly used ones in agricultural biogas plants. Compounds with particular polyphenolic structures appeared among the most distinctive markers. Analysis of samples collected during acidogenic phase and unstabilized methanogenesis indicates for- mation of certain dihydro-flavonoids in early stages of the process and their consequent degradation. Due to formerly described higher toxicity of some dihydroflavonoids (e.g. taxifolin) compared to their more common counterparts (e.g. quercetin, malvidin etc.), unstabilized digestate would represent a potential environmental risk when used as a fertilizer deserving a proper control. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Anaerobic fermentation is an effective ecological waste treat- ment process and a method for production of cheap electrical and thermal energy. The most widespread biogas production method is a “wet” anaerobic fermentation based on fermenting of feedstock material mixed with a liquid medium. The process of biogas for- mation has already been well described (Weiland, 2010). Briefly, it consists of several stages; i) decomposition of lipids, proteins and polysaccharides (mainly by hydrolysis) in feedstock by aerobic microorganisms (oxygen content is still high) (Archer and Peck, 1989), ii) acidogenesis e decomposition of higher fatty acids to lower ones, i.e. acetic, caproic, valeric, butyric, propionic acids and their iso forms and iii) methanogenesis e action of Acetotrophic and Hydrogenotrophic Archaea (Li et al., 2011). One of the easily available source of plant residua for biogas production is wine industry, which generates huge amount of various kinds of waste, i.e. grape stalk, grape marcs, exhausted yeast and wine lees (Bustamante et al., 2008). The efficiency of anaerobic digestion of wine waste was already studied by many authors mainly using gas chromatography (Melamane et al., 2007; Da Ros et al., 2014; Leiva et al., 2014; Fabbri et al., 2015; Li et al., 2015). However, the lack of nutrients, low pH of feedstock mate- rial and the inhibition of biodegradation by the presence of poly- phenols and copper significantly complicates the process of wine waste anaerobic fermentation as described in the study by * Corresponding author. E-mail address: petr.bednar@upol.cz (P. Bedn ar). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere http://dx.doi.org/10.1016/j.chemosphere.2016.09.124 0045-6535/© 2016 Elsevier Ltd. All rights reserved. Chemosphere 166 (2017) 463e472