Mass spectrometry characterization of lipopeptides The HPLC purified individual lipopeptide fractions were collected, confirmed their purity by reinjection into HPLC and used for the structure
determination by MALDI-TOF mass spectrometry. Results of analysis of all HPLC fractions revealed the presence of various lipopeptide species. The mass ion with m/z 984/985 Da was observed in fractions of lipopeptides produced by all strains (Table 1) and the GC MS analysis for fatty acid identification suggested that it had a β-hydroxylated C15 fatty acid. Additional GC-MS analysis of all HPLC purified fractions documented the presence of β-hydroxy fatty acid with a chain length from C7 to C17. The fractions Fr-c and Fr-e found commonly in strains S-3 and S-11 showed high antimicrobial activity and the molecular mass determined for these lipopeptides were m/z 1495 LY3023414 manufacturer and 1065, respectively (Figure 4). The fatty acid analysis revealed that fractions Fr-c and Fr-e contained β-hydroxy fatty acids with chain lengths C17 and C14 respectively, suggesting that these compounds belong to the antimicrobial lipopeptide family fengycin and iturin respectively. Further, the amino acid sequence obtained for the fraction Fr-c (EOrnYTEVPEYV) confirmed it as a member
of fengycin family. The molecular mass and fatty acid composition of fraction with m/z 1043 (Fr-a of sample S-6) assigned it to this website lipopeptide group surfactin. Other antimicrobial mass ions produced by these strains include m/z 607, 637, 4-Aminobutyrate aminotransferase 679, 721, 746, 1153, 1180, 1522 and 1535. Figure 4 MALDI MS spectrum of Fr-c and Fr-e from strainS-3 (identical spectrum is observed with the Fr-c and Fr-e of the strain S-11).
Table 1 List of masses observed in fractionated lipopeptides from different samples obtained in positive ion linear mode Sample name HPLC fraction number Mass (m/z) SD Sample S-3 Fr-a 985.13 0.0021 Fr-b 985.73 0.0037 Fr-c 1495.11 0.0069 Fr-d 1522.52 0.003 Fr-e 1065.22 0.0034 Fr-f 607.21 0.01 Sample S-4 Fr-a 679.57 0.0052 Fr-b 984.82 0.01 Sample S-5 Fr-a 679.69 0.0092 Fr-b 984.77 0.01 Fr-c 637.06 0.05 Fr-d 746.17 0.0042 Sample S-6 Fr-a 1043.66 0.01 Fr-b 984.96 0.0059 Fr-c 637.01 0.0071 Sample S-7 Fr-a 1180.01 0.022 Fr-b 985.01 0.015 Fr-c 721.25 0.0011 Sample S-9 Fr-a 1536.16 0.0092 Fr-b 984.57 0.01 Sample S-10 Fr-a 1535.21 0.0074 Fr-b 984.21 0.0098 Sample S-11 Fr-a 1153.65 0.0075 Fr-b 984.22 0.0012 Fr-c 1495.43 0.0045 Fr-d 637.23 0.025 Fr-e 1065.21 0.01 Sample S-12 Fr-a 679.23 0.003 Fr-b 984.14 0.0091 The calculations of standard deviation (SD) were done using MS Excel Descriptive Statistics for each ion measurements (n=4), mi is the measured mass and following is the formula: . Discussion Several reports have described that soil microbes are worthy to be used as the AZD1152 source of different antimicrobial substances including peptides for versatile applications .