Abstract
An antifungal protein produced by Bacillus licheniformis strain BS-3 was purified to homogeneity by ammonium sulfate precipitation, DEAE-52 column chromatography and Sephadex G-75 column chromatography. The purified protein was designated as F2 protein, inhibited the growth of Aspergillus niger, Magnaporthe oryzae and Rhizoctonia solani. F2 protein was a monomer with approximately molecular weight of 31 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gave a single peak on High Performance Liquid Chromatography (HPLC). Using Rhizoctonia solani as the indicator strain, the EC50 of F2 protein was 35.82 µg/mL, displaying a higher antifungal activity in a range of pH 6.0 to pH 10.0, and at a temperature below 70 °C for 30 min. F2 protein was moderately resistant to hydrolysis by trypsin, proteinase K, after which its relative activities were 41.7% and 59.5%, respectively. F2 protein was assayed using various substrates to determine the enzymatic activities, the results showed the hydrolyzing activity on casein, however, no enzymatic activities on colloidal chitin, CM-cellulose, xylan, M. lysodeikticus, and p-nitrophenyl-N-acetylglucosaminide.
Highlights
Bacillus licheniformis is a saprophytic bacterium that is widespread in Nature
We introduced the isolation and partial characterization of a 31 kDa antifungal protein produced by B. licheniformis BS-3
The culture supernatant of BS-3 was filtered by filter-sterilizer. 600 mL of the filtrate was divided into six aliquots, precipitated with solid ammonium sulfate, The results showed that the optimal saturation of ammonium sulfate was 50% for precipitating antifungal protein (Figure 1)
Summary
Bacillus licheniformis is a saprophytic bacterium that is widespread in Nature. It has been applied widely to produce proteases [1], amylases [2], lactamase [3], antibiotics [4], surfactin [5] and specialMolecules 2012, 17 chemicals [6] in the fermentation industry with low risk of adverse effects to human health or the environment. Bacitracin, the first peptide antibiotic derived from cultures of B. licheniformis, has been applied widely in the medical and veterinary area, and several other peptide antibiotics from different. Three bacteriocin-like peptides named lichenin, bacillocin 490 and P40 produced by. B. licheniformis strain 26 L-10/3RA, 490/5 and P40, respectively, have been reported [1,8,9]. These three bacteriocin-like peptides have different molecular mass, heat resistance, antagonistic spectrum and insensitivity to trypsin, and showed antagonistic activity against Staphylococcus aureus, and fungal species. A low-molecular-weight bacteriocin-like protein from B. licheniformis MKU3 exhibited a wide spectrum of antimicrobial activity against several Gram-positive bacteria, several fungi and yeast. B. licheniformis ZJU12 is isolated from soil, its cell-free supernatant exhibites marked antibacterial and antifungal activities, after treatment with proteinase K and trypsin, The antagonistic activity is lost completely by treating with proteinase
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