In the first approaches in tissue culture, mainly complex additives such as protein hydrolysates were used, for example to supply organic nitrogen. Over time, these were reduced to additives with lower complexity, such as amino acid mixtures, if comparable results could be achieved. In some cases, this even led to a reduction to single amino acids.
Due to their natural origin and the processing procedures, complex additives can sometimes exhibit very strong fluctuations. By using single amino acids or their mixtures, protocols with more precisely defined media can be developed. This can improve the reproducibility considerably.