Comprehensive Characterization of Janthinobacterium kumbetense sp. nov. (GKT): Industrial Enzyme Production, Antimicrobial Resistance and Optimization of Violacein Production with Its Bioactive Properties

In this study, we aimed to screen for Janthinobacterium kumbetense GKT strain production of industrially important enzymes and to assess its antimicrobial resistance profile. Additionally, to enhance violacein production by GKT strain, we investigated the optimum cultivation conditions for this bacterium and the biological properties of crude violacein extract, including its antimicrobial and antioxidant activities. The GKT strain demonstrated proteolytic, lipolytic, and chitinolytic activities. Furthermore, the antibiotic susceptibility test showed that it was resistant to 5 out of the 15 antibiotics tested. Subsequently, the effects of different growth media, temperatures, pH levels, agitation rates, inoculum amounts, incubation times, carbon and nitrogen sources, and NaCl concentrations on violacein production by the GKT strain were examined. The maximum violacein yield of 28.7 μg/ml was achieved when the strain was incubated at 22°C for 72 hours under static conditions in nutrient broth with a pH of 6.4. Also, violacein yield increased with the addition of 1% pepton and 1% glucose as nitrogen and carbon sources, respectively. Violacein pigment, extracted using either methanol or ethanol, was found to inhibit the growth of S. aureus, S. epidermidis, B. cereus and E. faecalis. However, no-activity was seen on tested fungus strains. Additionally, violacein showed antioxidant activity against ABTS and DPPH radicals with IC50 values of 307 μg/ml and 261 μg/ml, respectively. Current research findings suggest that violacein pigment of GKT strain has potent antimicrobial and antioxidant activities and can be used in applications in the pharmaceutical industry.