A total of 416 actinomycete cultures were isolated from various unique environments in Ethiopia and tested for bioactivity. Six isolates with pronounced antimicrobial activity were chosen for taxonomic identification and further investigation. Morphological and cultural properties of the isolates were found to be consistent with those of the genus Streptomyces, which was further confirmed by phylogenetic analysis based on 16S rRNA gene sequences. One of the isolates, designated Streptomyces sp. Go-475, which displayed potent activity against both pathogenic yeasts and Gram-positive bacteria, was chosen for further investigation. Metabolite profiles and bioactivity of Go-475 incubated on wheat bran-based solid and soya flour-based liquid media were compared using high-resolution LC-MS. This allowed identification of several known compounds, and suggested the ability of Go-475 to produce new secondary metabolites. Major anti-bacterial compounds were purified from liquid cultures of Go-475, and their structures elucidated by NMR and HRMS as 8-O-methyltetrangomycin and 8-O-methyltetrangulol. In addition, many potentially novel metabolites were detected, the majority of which were produced in solid media-based fermentation. The genome sequence of Streptomyces sp. Go-475 was obtained using a hybrid assembly approach of high quality Illumina short read and low quality Oxford Nanopore long read data. The complete linear chromosome of 8,570,609 bp, featuring a G+C content of 71.96%, contains 7,571 predicted coding sequences, 83 t(m)RNA genes, and six rrn operons. Analysis of the genome for secondary metabolite biosynthesis gene clusters further confirmed potential of this isolate to synthesize chemically diverse natural products, and allowed to connect certain clusters with experimentally confirmed molecules.

In this study the first supercritical fluid based protocol for the extraction, analysis, and isolation of six polar compounds, i.e., o-vanillin (), styracin (), vanillin (), trans-cinnamic acid (), vanillic acid (), and shikimic acid (), was developed. First, eight styrax resin products (R1-R8) obtained from various tree species, which are known to contain compounds-, were extracted with a 1 : 1 mixture of supercritical CO and EtOH. Within 4 minutes, the compounds were successfully baseline separated on an Acquity UPC BEH 2-EP (3.0 × 100 mm, 1.7 µm) column using a mobile phase of supercritical CO and MeOH with 0.1 % phosphoric acid. The compounds were quantified and the method was validated according to current ICH guidelines. Scaling up to preparative supercritical fluid chromatography using a Viridis BEH 2-EP (10 × 250 mm, 5 µm) column allowed for a fast separation and isolation of the selected constituents and from R6 within 7 minutes. This supercritical fluid protocol is easily adaptable to compounds of similar polarity. The increase in speed and its environmental friendliness underline its superiority over conventional set-ups.