Development of fed-batch strategies for the production of streptavidin by Streptomyces avidinii based on power input and oxygen supply studies.

Streptavidin is a tetrameric protein with an extremely high affinity to biotin and different biotin-like peptide-tags. This characteristic causes its widespread use in biotechnology. Streptavidin is produced by the fermentation of wild type Streptomyces avidinii or by recombinant Streptomyces lavendulae, Escherichia coli, and Bacillus subtilis strains. However, little is known about the influence of power input and oxygen supply as well as feeding strategies on the production of streptavidin by S. avidinii. This paper provides a systematic analysis of the effect of rotary frequency of the stirrer, leading to a plateau-like streptavidin formation behaviour between 400 and 700 min(-1). This plateau was characterized by specific power inputs between 79 and 107 W L(-1) and corresponding maximal product concentrations of 6.90 μM in 6 days. Lower as well as higher rotary frequencies were not beneficial. Subsequently, a linear fed-batch procedure could be established reproducibly yielding 39.20 μM streptavidin in 14 days, characterized by a constant productivity of 114 nM h(-1). Fed-batch procedures based on dissolved oxygen were less efficient. The linear feeding strategy presented in this paper led to the highest streptavidin concentration ever reported and exceeded the maximal product level given in the literature drastically by a factor of 8.5.