Chemical Constituents And Antimicrobial Activity Investigations Of Bacillus Atrophaeus

In the thesis,the secondary metabolites of Bacillus atrophaeus were investigated in several contexts.After the optimization of culture conditions,large scale culture was carried out to get sufficient material for chemical analysis.As a result,nine compounds were isolated from different extracts.In the methanol phase,iturin A2(1),iturin A4(2),iturin A6(3),iturin A8(4)are the major components,while the ethyl acetate phase yielded four indole-derived compounds: N-acetyltryptamine(5),bacillamide A(6),N-formyltryptamine(7)and bacillamide C(8).In the butanol phase,one amino acid phenylalanine(9)was isolated.The structure elucidations of the compounds were carried out by comparing the NMR and MS spectra with known compounds.Compounds 1-4 belong to a class of antifungal antibiotics,and it was necessary to induce the production of compounds in order to increase yields.The iturins are biosynthesized from amino acids and fatty acids.We fed amino acids and fatty acids separately to Bacillus atrophaeus IMG2-11;after extraction using methanol,we found not all of the amino acids composing the iturins act as inducers of production.In our assay,Tyr yielded the largest improvements,increasing the production of iturins significantly.In contrast,addition of small fatty acids had no effect on the production of iturins.Interestingly,feeding some amino acids also increased the production of N-acetyltryptamine(5).The antimicrobial activities of iturins were tested by measuring the MIC value.The four compounds exhibited promising activity against Rhizopus stolonifer(MIC = 8.33 μg/m L)and weak activity against Candida species(MIC = 66.7 μg/m L).