Eco-engineering of fermentative microbial communities: the role of keystone species
Résumé
Microbial mixed cultures present a broad metabolic flexibility and allow considering complex organic biomass as potential resources for biomolecules and hydrogen production in dark fermentation processes. A wide number of microbial species are able to ferment carbohydrates, but a high microbial diversity is often detrimental to bioprocess operation since it leads to process instability. To date, only few controllers, essentially physicochemical, are available to control finely the multiplicity of bacterial metabolisms in mixed cultures. And no strong or very specific selection pressure could be applied to enrich in efficient and robust microbial communities. One possibility would be to engineer ecologically these communities to better control the metabolic networking. For that, we investigated the use of keystone species as biotic triggers of the fermentative metabolism in mixed cultures. First some keystone species, often low in abundance but having a major role on metabolic networks, were identified from several natural ecosystems. Different strategies of biotic control of the fermentative microbial communities were then investigated, confirming the important role of these species and the possibility of using them as biotic controllers of the overall community. Artificial co-cultures were also carried out, and a specific type of interaction was characterized. Beyond this study, it is expected that these findings lead to new biotechnological or environmental applications through the use of biotic control of microbial metabolisms.