Background

Food ways and dietary habits, offer significant insight into subsistence strategies, connectivity and cultural and ideological choices of societies (Beaudry and Metheny, 2015). This direction of research is rather restricted when applied to ancient societies, as only residues of food have survived the absence of preservatives. Fragmentary evidence has impeded research of ancient fermented alcoholic beverages such as beer, wine, mead (honey wine) and kvass, which played a major role in daily life as well as in religious, social and political rituals of ancient societies (Joffe, 1998; Myers et al., 2000; Dietler, 2006; Legras et al., 2007; McGovern, 2009; Schiefenhövel and Macbeth, 2011; Hornsey, 2012; Parker and McCool, 2015).

Reconstruction of ancient fermented beverages has, until now, consisted of brewing modern ingredients according to ancient recipes or based on organic residue found in ancient containers or breweries. To achieve fermentation, previous efforts have used Saccharomyces cerevisiae, the domesticated commercial yeast species (McGovern, 2009; Stika, 2011). To the best of our knowledge, the study of ancient microorganisms, including bacteria (Donoghue et al., 2004; Andam et al., 2016), viruses (Muhlemann et al., 2018) and yeast (Cavalieri et al., 2003), was based on ancient DNA studies; no attempt has been made to isolate and reproduce microorganisms from containers used for the production of fermented beverages.

Hypothesizing that yeast can form stable colonies in clay nanopores, we were recently able to isolate live yeast cells from ancient containers thought to have contained beverages and oil, using the current protocol (Aouizerat et al., 2019). Following the isolation, we characterized the growth of the yeast, sequenced and analyze their full genome and used them to produce and analyze beer and mead (Aouizerat et al., 2019).

Thus, our research suggests that ancient microorganisms can be isolated from archaeological finds, facilitating the identification of additional ancient foods and beverages. It also promotes the field of “experimental archeology”: the recreation of the past, mainly of ancient fermented food (such as cheese and pickles) and beverages.

The following text presents a two-part protocol for the collection of sherds/vessels from archeological dig sites, as well as the isolation and characterization of microorganisms. Part I details guidelines for handling vessels intended for microorganisms’ isolation. Part II describes the isolation process. While this protocol was applied to yeast, it can be easily modified to apply to other microorganisms, such as bacteria.