Ricerc@Sapienza

We initially devised this Research Topic (RT) as a valuable initiative to collect high-quality scientific articles from the participants of the 4th European Federation of Biotechnology (EFB) Microbial Stress meeting held in Kinsale, Ireland, April 2018. The scope of the RT is based on the scientific content of that “Microbial Stress: from Systems to Molecules and back” meeting. Indeed, over 40% of the articles eventually accepted for publication were contributed by meeting participants, but notably the remaining 60% was contributed by authors that work in this field.

Microbes from the three domains of life, bacteria, archaea and eukarya, share the need to sense and respond to changes in the external and internal concentrations of protons. When the proton concentration is high, acidic conditions prevail and cells must respond appropriately to ensure that macromolecules and metabolic processes are sufficiently protected to sustain life.

Cheese whey (CW) is the main by-product of the cheese making process and is composed mainly by lactose, proteins, lipids and mineral salts. The environmental impacts and other potential negative effects linked to the traditional management strategies of CW are no longer considered sustainable, therefore alternatives need to be explored. Dark fermentation (DF) may be a promising approach for CW valorization.

Batch dark fermentation tests were performed on sheep cheese whey without inoculum addition at different operating pHs, relating the type and production yields of the observed gaseous and liquid by-products to the evolution of fermentation. Cheese whey fermentation evolved over time in two steps, involving an initial conversion of carbohydrates to lactic acid, followed by the degradation of this to soluble and gaseous products including short-chain fatty acids (mainly acetic, butyric and propionic acids) and hydrogen.