Bioprocessing strategies for cost-effective large-scale biogenic synthesis of nano-MgO from endophytic Streptomyces coelicolor strain E72 as an anti-multidrug-resistant pathogens agent.

In this report, the local nano-MgO synthesizer strain has been isolated from Ocimum sanctum plant and deposited in GenBank as endophytic Streptomyces coelicolor strain E72. Its intracellular metabolic fraction that contains 7.2 μg/μl of carbohydrate, 6.3 g/l of protein and 5.2 nmol/hr/ml of nitrate reductase used to produce multi-surface shaped nano-MgO with diameter ~25 nm. To the best of our knowledge, this is the first report using statistical nanobiotechnological strategies (Plackett -Burman, Box-Behnken and Taguchi experimental designs) to study and evaluate the endophytic S. coelicolor biomass production (123.3 g/l) and extract the highest bioactive metabolites that used for biogenic synthesis of nano-MgO (320 g/l) through exponential sucrose pulses feeding fermentation strategy after 192 hr in semi industrial scale bioreactor (7 L). Purified nano-MgO applied in vitro against multi-drug resistant human pathogens and the large inhibition zone recorded against Shigella flexneri (108 ± 10.53 mm). The average of MICs was recorded as 25 µg/ml that inhibited 90% of the pathogenic living cells and compared with 100 mg/ml ampicilin/sulbactam solution that killed 40% of the same pathogen. These results are expected to gather sufficient knowledge to discover and develop a new cheap and eco-friendly nano-MgO as an extremely strong antimicrobial agent used in biomedical applications.