Multi-Response Optimization of Granaticinic Acid Production by Endophytic Streptomyces thermoviolaceus NT1, Using Response Surface Methodology

Abstract

Streptomyces thermoviolaceus NT1, an endophytic isolate, was studied for optimization of granaticinic acid production. It is an antimicrobial metabolite active against even drug resistant bacteria. Different media, optimum glucose concentration, initial media pH, incubation temperature, incubation period, and inoculum size were among the selected parameters optimized in the one-variable-at-a-time (OVAT) approach, where glucose concentration, pH, and temperature were found to play a critical role in antibiotic production by this strain. Finally, the Box–Behnken experimental design (BBD) was employed with three key factors (selected after OVAT studies) for response surface methodological (RSM) analysis of this optimization study.RSM analysis revealed a multifactorial combination; glucose 0.38%, pH 7.02, and temperature 36.53 °C as the optimum conditions for maximum antimicrobial yield. Experimental verification of model analysis led to 3.30-fold (61.35 mg/L as compared to 18.64 mg/L produced in un-optimized condition) enhanced granaticinic acid production in ISP2 medium with 5% inoculum and a suitable incubation period of 10 days. So, the conjugated optimization study for maximum antibiotic production from Streptomyces thermoviolaceus NT1 was found to result in significantly higher yield, which might be exploited in industrial applications.

Bioactivity study and metabolic profiling of Colletotrichum alatae LCS1, an endophyte of club moss Lycopodium clavatum L.

“…For Response surface methodology (Box Behnken design), four combinatorial factors had been checked for their together influence on highest antibacterial production (prime component bisabolol) against the potent antibiotic resistant strain MRSA. Endophytic microbiota showing highest response in presence of glucose as prime carbon source, yeast extract as the organic nitrogen source and vitamin precursors has been previously reported by [ 21 ]. Increase in glucose concentrations cause a rapid increase in fungal biomass but stress is directly proportional to production of secondary metabolites.…”

“…For the better understanding of the fungal hyphal structures scanning electron microscopy was done after proper pre-treatment and appropriate desiccation of the fungal sample. The samples were slowly dehydrated in different gradations of ethanol ranging from 10% to 90% to avoid the shrinking of the mycelial structures and then critically point dried, coated with gold and examined with a Zeiss EVO18 scanning electron microscope following the standard protocols [ 21 ].…”