Improving Conditions for Gliotoxin Production by Local Isolates of Aspergillus fumigatus

Thirty two isolates of Aspergillus fumigatus were obtained from a total of 44 samples of sputum, nose swab and tracheal aspirate from suspected patient with aspergillosis were also collected from February 2014 to June 2014. A morphological examination of A. fumigatus was first made with naked eye and at low magnification power of microscope after that detailed examination was done by measuring the dimensions of the microscopic structures, photographing the microscopic structures and using relevant literature. Results appeared conical-shaped terminal vesicles, uniseriate row of phialides on the upper two thirds of the vesicle, conidiophore stipes were short, phialides arrange uniseriate upper vesicle conidia and parallel to axis of conidiophore, produced in chains of spore basipetally from phialides, the chains of spore were borne directly in the absence of metulae and represented by septet and branching hyphae. The ability of A. fumigatus for GT production was investigated using thin layer Chromatography (TLC) and High Performance Liquid Chromatography (HPLC) techniques and results showed that GT was produced by 81.25% of A. fumigatus isolates. Optimum conditions for GT production by A. fumigatus 16 (AF-16) isolate were determined by submerged fermentation using Yeast extract sucrose medium. Results indicated that AF-16 isolate was the highest GT producer on Yeast Exract Sucrose medium with inoculum size 2×107 conidium and incubation at 32ºC for 15 days and the concentration of gliotoxin was (4511µg mL-1).

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Polyphasic Assessment of Aflatoxin Production Potential in Selected Aspergilli

Toxins ◽

10.3390/toxins11120692 ◽

2019 ◽

Vol 11 (12) ◽

pp. 692

Author(s):

Stephen Abiola Akinola ◽

Collins Njie Ateba ◽

Mulunda Mwanza

Keyword(s):

Yeast Extract ◽

High Performance ◽

Aflatoxin Production ◽

Neutral Red ◽

Polymerase Chain ◽

Contamination Levels ◽

Internally Transcribed Spacer ◽

Aflatoxin B2 ◽

Layer Chromatography ◽

Yeast Extract Sucrose

This study investigated the aflatoxin production potentials of selected fungi using a polyphasic approach. Internally transcribed spacer region of the fungi was amplified using the polymerase chain reaction. Forty-five Aspergillus strains were further assessed for aflatoxin production using the conventional methods such as growth on yeast extract sucrose, β-cyclodextrin neutral red desiccated coconut agar (β-CNRDCA); expression of the aflatoxin regulatory genes and the use of both thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). A large proportion (82.22%) of the isolates harbored the Nor-1 gene while 55.56%, 68.89%, and 80% possessed the ver-1, omt-A, and aflR genes, respectively. All 100% the isolates harbored the aflJ gene. Twenty-three isolates were positive for aflatoxin production based on the yeast extract sucrose medium (YES) test; ammonium vapor test (51%), yellow pigment production (75.5%), and β-CNRDCA tests; and blue/green fluorescence (57.7%). Based on TLC detection 42.2% produced aflatoxins while in the HPLC, total aflatoxin (AFTOT) production concentrations ranged from 6.77–71,453 µg/g. Detectable aflatoxin B1 (AFB1) concentrations obtained from the HPLC ranged between 3.76 and 70,288 µg/g; 6.77 and 242.50 µg/g for aflatoxin B2 (AFB2); 1.87 and 745.30 µg/g for aflatoxin G1 (AFG1); and 1.67 and 768.52 µg/g for aflatoxin G2 (AFG2). AFTOT contamination levels were higher than European Union tolerable limits (4 µg/kg). The regression coefficient was one (R2 = 1) while significant differences exist in the aflatoxin concentrations of Aspergillus (p ≤ 0.05). This study reports the potentials of Aspergillus oryzae previously known as a non-aflatoxin producer to produce AFG1, AFG2, AFB1, and AFB2 toxins. Aspergillus species in feedlots of animals reared for food are capable of producing aflatoxins which could pose hazards to health.

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