Enhanced characterization of yeast hydrolysate combining acid digestion and 1D-1H NMR targeted profiling

Abstract

Yeast extract, or autolysate, is a required component for many cell-culture media, but its exact constituents and benefits are unknown. Yeast extract contains a diverse assortment of metabolites, often present in complex forms (eg, polypeptides and polynucleotides). This study employs one-dimensional proton nuclear magnetic resonance (1D-1H NMR) spectroscopy to analyze free (ie, readily available) components present in commercially available yeast autolysate. The product is monitored while further subjected to acid hydrolysis, allowing for a more robust understanding of the exact components present, particularly those contained in complex forms. The amino acids and glucose compounds behaved as expected based on other acid hydrolysis studies, and were modelled similarly. Parameter estimation was in strong agreement with pre-hydrolysis targeted 1D-1H NMR profiling. This analysis was expanded to components not as thoroughly investigated and was especially applicable to nucleic compounds. Acid hydrolysis revealed that the yeast extract was approximately 5.4% nucleic material by weight, mostly composed of adenosine, and largely provided by RNA due to the presence of uracil and lack of thymidine. Choline-containing compounds were also positively identified with an observable increase of free choline during hydrolysis. 1D-1H NMR spectroscopy allowed for the simultaneous monitoring of a significant number of yeast-extract metabolites, some of which were previously unreported. Utilizing 1D-1H NMR spectroscopy in conjunction with acid hydrolysis led to a more complete view of the compounds present, and accounted for an additional 24% of the yeast-extract mass.