Technical note: Electrochemical and chemical complications resulting from yeast extract addition to stimulate microbial growth

Abstract

Addition of 1 g/L yeast extract (YE) to sterile, aerobic (approximately 21% dissolved oxygen) and deoxygenated (<0.0001% dissolved oxygen) natural seawater fixed the corrosion potential (Ecorr) of 316L (UNS S31603) stainless steel. YE contains riboflavin and other B vitamins that can act as redox mediators, sorb to surfaces, and chelate metal ions. As demonstrated, YE alters the pH of buffered media, including natural seawater. These same activities are typically attributed to microorganisms and are related to microbiologically influenced corrosion (MIC) mechanisms. Despite the prevalent use of YE to stimulate microbial growth in MIC experiments, the potential impact of YE on the outcome of those experiments has not been examined.