Combined effect of Al2O3 microparticle-enhanced cultivation (MPEC) and inoculation strategy on Streptomyces rimosus

Actinomycetes play a key role in modern biotechnology, serving as a rich source of bioactive compounds. One of the approaches to stimulate filamentous microorganisms in the production of secondary metabolites is microparticle-enhanced cultivation (MPEC). In this study MPEC was applied for Streptomyces rimosus in 5.5 L stirred tank bioreactors with the use of Al 2 O 3 microparticles. Two inoculation strategies were proposed. These were the inoculation of the bioreactor containing microparticles with spore suspension and the inoculation of the bioreactor with microparticle-enhanced precultures. The levels of oxytetracycline, 2-acetyl-2-decarboxamido-oxytetracycline (ADOTC), enaminomycin B, spinoxazine A, lorneic acid J, rimocidin, rimocidin CE-108, milbemycin A 3 , and milbemycin β 11 indicated that the application of Al 2 O 3 microparticles to S. rimosus cultivations is a promising method for enhancing its biosynthetic performance. The effect of microparticles was associated with the reduction in the size of morphological objects. However, the overall outcome of MPEC was determined by both the optimal microparticle concentration and the choice of the inoculation strategy. In the case of Al 2 O 3 microparticles, their application at a concentration of 15 g L − 1 in S. rimosus preculture-inoculated cultivation increased oxytetracycline production by up to 33%. In contrast, the biosynthesis of this metabolite was inhibited when the bioreactor was inoculated with spore suspension.