Boosting Bioprocess Performance By Yeast Extracts: It´s All in the Mix

Yeast extract is widely used in industry to boost cell growth and enhance productivity, titer and product yields in fermentation processes. Opposed to chemically defined media, it has the benefits of providing not only ready to use complete building block for cells, but it also contains a range of cofactors, vitamins and growth factors. However, being such a complex mixture of nutrients, generally little is known on which components in the yeast extract are responsible for its beneficial results. Moreover, it is generally not known to biotechnologists that yeast extract can be highly different in composition. As a result, process optimization by adding yeast extract is generally only reviewed on a very basic level, and only a few different yeast extracts are tested.

To review the impact yeast extract can have on fermentation processes, a study was conducted in which the effect of three highly different yeast extract (combination)s on the performance of a range of micro-organisms was evaluated. In particular, (combinations of) Ohly^® KAF/KAT (a yeast extract high in free amino acids), Ohly^® Flav-R-Ound (a yeast extract containing relatively high nucleotide concentrations) and Ohly^® Flav-R-Tide (a yeast extract high in peptides) were tested in this study. They were reviewed with a 10-point experimental design to find an optimal blend for a range of industrial relevant organisms. In addition, the same blend optimization was reviewed for one organism at different conditions.

The results show that there is clearly not a ´golden standard´ of a yeast extract that works optimally with all micro-organisms, or even for the same organism cultivated under different conditions. With that, it also shows a potential for process optimization, if the right combination of yeast extracts is supplied. The experimental approach of testing ten blends as applied in this research shows to be a simple pragmatic approach to improve industrial production processes without the need for indepth knowledge about the exact composition of the yeast extract.