Characterization and regulation of new secondary metabolites fromAspergillus ochraceusM18 obtained by UV mutagenesis

Abstract

UV irradiation of Aspergillus ochraceus NRRL 3174 conidia led to stable mutations in ochratoxin and penicillic-acid pathways. These mutants, especially M18, produced an unexpectedly large number of new metabolites. Two new compounds were purified by TLC and HPLC and their chemical structures were determined. They are 2,10-dimethyl 4-hydroxy-6-oxo-4-undecen-7-yne (1) and 4-(3-methyl-2- butenyl) oxy 1-phenyl acetic acid (2). Compound 1 is very active against Gram-positive bacteria, such as Staphylococcus aureus and Bacillus subtilis, but inactive against Gram-negative bacteria, fungi, and yeasts. However, compound 2 has no antibiotic activity. The production of 1 was generally associated with growth, whereas that of compound 2 was dissociated from growth. The biosynthesis of these 2 metabolites was influenced by the sources of carbon and nitrogen.

Isolation of Bacillus spp. from Thai fermented soybean (Thua-nao): screening for aflatoxin B1and ochratoxin A detoxification

“…The chloroform phase was recuperated and then evaporated under nitrogen gas at 65°C (90 rev min −1 ) until dry. The samples were then dissolved in 1 ml methanol (Fisher Scientific), filtered (Millex ® HV PVDF 0·45 μ m) and analysed by HPLC as described by Awad et al. (2005).…”

Amplification and diversity analysis of ketosynthase domains of putative polyketide synthase genes in Aspergillus ochraceus and Aspergillus carbonarius producers of ochratoxin A

“…Conidia (final concentration of 10 6 spores/mL) were inoculated into 250 mL Erlenmeyer flasks containing 100 mL of synthetic medium at 258C, without shaking. Synthetic medium was prepared according to Awad et al [14]. Mycelium was harvested by filtration through a 0.45 lm filter (Millipore), frozen in liquid nitrogen, and then stored at -808C before nucleic acid extraction.…”

“…The organic phase was taken and concentrated under vacuum to dryness, and the residue was redissolved in 0.5 mL of methanol. A volume of 80 lL of the sample was analyzed by HPLC to detect penicillic acid as described by Awad et al [14].…”

<i>ULTRAVIOLET MUTAGENESIS OF LOCAL ISOLATE Trichoderma sp. T065 FOR IMPROVING CELLULASES ACTIVITY </i>(Mutagenesis Isolat Lokal<i> Trichoderma sp. </i>T065 menggunakan Ultraviolet untuk meningkatkan Aktivitas Selulase)

“…The colonies appeared from every UV treatment were counted and compared with those 200 conidia of non-UV-treated T065 spread on the same agar. The UV mutants were obtained according to method described by Awad et al (2005) with slight modifications. The plates without lids containing spore suspension of wild Trichoderma sp.…”