Optimised Fermentation Production of Radiolabelled Ochratoxin A by Aspergillus ochraceus with Maximum 14C in the Pentaketide Moiety for Exploring Its Rat Renal Toxicology

In the context of the mysterious Balkan endemic nephropathy of the 1900s, and the discovery in the 1960s of the potent mycotoxin ochratoxin A, experimental research projects sought to explore any inter-relationship. Experimental lifetime administration of the toxin to male rats had revealed renal DNA adducts with the toxin, correlated with renal tumours, confirmation of which required molecular evidence. Consequently, production of 14C-ochratoxin A of a high specific radioactivity was required, practical biosynthetic detail of which had not previously been published. A fermentation study of Aspergillus ochraceous was carried out during 2002 for a European project, to select for the production of high-quality 14C-ochratoxin A, necessarily exploring for the maximum diversion of 14C-sodium acetate into the pentaketide portion of mycotoxin. Experimentation necessarily had to optimise the competitive context of fungal growth dynamics and addition of the biosynthetic precursor in the early days of shaken-flask fermentation before adding the radiolabelled precursor. From optimal fermentation, 50 mg of the 14C ochratoxin A was supplied within a European project for DNA adduct experimentation, but that proved negative as subsequently published. Experimental description of the radiolabelled ochratoxin A production was later made in a doctoral thesis, but is first publicised here. Further review of the literature reveals an explanation for the published failure to confirm rat DNA/ochratoxin A adduct formation, for which further experimentation is now recommended.

Aspergillus ochraceus biocontrol by Hanseniaspora opuntiae in vitro and on coffee fruits

Aspergillus ochraceus is an ochratoxin-producing fungus which contaminates coffee. In this study the antifungal effect of the yeast Hanseniaspora opuntiae on three Aspergillus ochraceus strains (IOC 4417, IOC 4462, Ao 14) was evaluated in vitro and on coffee fruits. H. opuntiae (106 and 107 cells mL-1) reduced in vitro fungal growth from 82% to 87%, when co-cultivated with A. ochraceus. The yeast cell free supernatant (CFS) inhibited conidial germination from 76.5% to 92.5%, and hyphal growth from 54% to 78%. The yeast (107 and 109 cells mL-1) applied on coffee fruits delayed fruit decay by A. ochraceus (IOC 4417 and Ao 14) until the 9th day, and was significantly different (p < 0.05) from the controls. Furthermore, the ultrastructure of the yeast-fungus interaction on the coffee fruit surface showed yeast attachment to A. ochraceus hyphae, and morphological alterations in fungal structures, with hyphal abnormalities, such as tortuous hyphae with irregular, non-uniform surface compared to the control without yeast. H. opuntiae showed efficacy as biocontrol agent and, to the best of our knowledge, this is the first study on the antifungal activity of H. opuntiae against A. ochraceus on coffee fruits Nevertheless, application of H. opuntiae to the crop in the field requires further studies.

Aspergillus ochraceus: Metabolites, Bioactivities, Biosynthesis, and Biotechnological Potential

Fungus continues to attract great attention as a promising pool of biometabolites. Aspergillus ochraceus Wilh (Aspergillaceae) has established its capacity to biosynthesize a myriad of metabolites belonging to different chemical classes, such as isocoumarins, pyrazines, sterols, indole alkaloids, diketopiperazines, polyketides, peptides, quinones, polyketides, and sesquiterpenoids, revealing various bioactivities that are antimicrobial, cytotoxic, antiviral, anti-inflammatory, insecticidal, and neuroprotective. Additionally, A. ochraceus produces a variety of enzymes that could have variable industrial and biotechnological applications. From 1965 until June 2022, 165 metabolites were reported from A. ochraceus isolated from different sources. In this review, the formerly separated metabolites from A. ochraceus, including their bioactivities and biosynthesis, in addition, the industrial and biotechnological potential of A. ochraceus are highlighted.

Dietary Trichosporon mycotoxinivoron modulates ochratoxin-A induced altered performance, hepatic and renal antioxidant capacity and tissue injury in broiler chickens

Ochratoxin A (OTA), an important fungal metabolite in foods and feeds has been shown to induce oxidative stress and cellular injuries to human and animal subjects. This study was designed to investigate the mode of action of a biological modifier Trichosporon mycotoxinivorans (TM), against OTA-mediated oxidative stress and tissue toxicity on broiler chickens. The birds were offered diets supplemented with OTA (0.15 and 0.3 mg/kg feed) and/or TM (0.5, 1.0 g/kg) for 42 days of age, and blood and tissue samples were collected to examine the oxidative stress, biochemical and histopathological parameters. Dietary OTA at all the tested levels induced the hepatic and renal tissue injury as indicated by significant decreased total antioxidant capacity in these organs along with significant decreased (p ≤ 0.05) serum concentrations of total proteins and albumin. The serum concentrations of alanine aminotransferase (ALT) and urea were significantly increased, and these observations were further supported by degenerative changes and increased relative weights of liver and kidneys. The dietary supplementation of TM at both tested levels relieved the detrimental impact of 0.15 and 0.3 mg OTA/kg on the studied parameters. The results of the study demonstrated that dietary TM significantly protects broiler chickens by reducing OTA-induced oxidative damage and tissue injury.

Aspergillus flavus and Aspergillus ochraceus inhibition and reduction of aflatoxins and ochratoxin A in maize by irradiation

Grains are susceptible to contamination by molds; some cause spoilage and others produce certain mycotoxins that cause a serious health threat to humans and animals. Aspergillus flavus and Aspergillus ochraceus and their mycotoxins, aflatoxins and ochratoxin A, are natural contaminants of various agricultural commodities. Control of these molds and their mycotoxins in food commodities is of utmost importance; therefore, the target of this research was to explore the effects of gamma irradiation doses on the growth of A. flavus and A. ochraceus in artificially inoculated yellow maize as well as on the production of aflatoxin B1, ochratoxin A, and the formation of toxins in maize. The irradiated dose of 6.0 kGy was found to completely inhibit the growth of the two molds, while a dose of 4.5 kGy reduced the production of their mycotoxins. Maximum degradation of the formed aflatoxins and ochratoxin A in maize occurred at 20 kGy, with best reduction rates of 40.1%, 33.3%, and 61.1% observed for aflatoxin B1, aflatoxin B2, and ochratoxin A, respectively. We recommend grains irradiation by gamma radiation at 6.0 kGy to decontaminate mycotoxin-producing molds before they produce mycotoxins. The study represents a proactive, efficient, and potent method for avoiding potential contamination of fungus during grains storage and transfer for one to two months.

Fungal bioremediation of olive mill wastewater: using a multi-step approach to model inhibition or stimulation

BACKGROUND

Olive mill wastewaters (OMWWs) possess a strong environmental impact; the use of fungi as tools for bioremediation could be a promising method.

RESULTS

Twenty-nine fungi were grown on minimal media supplemented with five different kinds of OMWWs (5-15%). Radial growth was assessed for 21 days and the data were modelled through the Dantigny-logistic like function to estimate τ, i.e. the time to attain half of the maximum diameter. Growth on potato dextrose agar and water agar (WA, minimal medium without supplementation) was used as reference. The differences in τ between PDA/WA and minimal media with OMWWs were modelled through a multi-factorial ANOVA, using the concentration of OMWW, the kind of wastes and fungi as categorical predictors. Finally, a principal component analysis was run to group and divide resistant and sensitive fungi. Some fungi experienced a positive Δτ, thus suggesting an inhibition by OMWW, whereas other isolates were enhanced.

CONCLUSIONS

Some isolates (for example Aspergillus ochraceus) showed a promising trend and could be possible candidates for a validation on a real scale. © 2016 Society of Chemical Industry.

Two primer pairs to detect OTA producers by PCR method

Fungi contaminating foods and feeds may produce many mycotoxins including ochratoxin A (OTA). Early and rapid detection of potential OTA producing fungi is important to reduce the negative impacts of OTA. In this study, two PCR specific primer pairs, AoLC35-12L/AoLC35-12R and AoOTAL/AoOTAR, were designed from a DNA sequence of a polyketide synthase gene in Aspergillus ochraceus NRRL 3174. On 14 different fungi tested by PCR, AoLC35-12L/AoLC35-12R amplified a unique band from either OTA or citrinin producers while AoOTAL/AoOTAR amplified one PCR product only from A. ochraceus. So these primers could be used to detect both OTA and citrinin producing fungi (AoLC35-12L/AoLC35-12R) or only A. ochraceus (AoOTAL/AoOTAR) from foodstuffs using PCR method.

The effect of bread making steps on the degradation of aflatoxins produced as a result of single inoculation with Aspergillus flavus and combined inoculation with Aspergillus flavus and Aspergillus ochraceus

This study aimed to determine the effect of bread making steps on the stability of aflatoxin. Sakha 8 wheat and Gemaiza 5 wheat cultivars, were used in the present study. They were inoculated with a dense spore suspension of toxigenic fungal species of Aspergillus flavus and a non toxigenic species of Aspergillus ochraceus singly and combined. Aflatoxin concentration was determined in the whole wheat grain, after milling, after fermentation, and after bread-baking process. Results showed that the highest reduction percentage for the total aflatoxins (81, G1 and G2), was in Sakha 8 (32.96%) (single treatment), Gemaiza 5 (19.54%) (single treatment ), Gemaiza 5 (18.65%) (combined treatment), and finally in Sakha 8 (16.49%) (combined treatment). There was no significant difference (p < 0.05) in aflatoxins content between Sakha 8 and Gemaiza 5 treated singly and in a combined way before and after milling process. In the mean time, the percentage of AFB1, AFG1 and AFG2 were reduced by 31.98%, 44.53% and 35.35%, respectively, while the total aflatoxins concentration were reduced by 41.17% after baking. Results also showed the presence of a significant difference at p < 0.05 among the whole grain, after milling and after baking concerning AFG1, AFG2 and the total aflatoxins content. No significant difference was found in case of AFB1.

Synthesis and antifungal activity of novel pyrano[2',3':4,5]thiazolo[2,3-b]quinazolines, pyrido[2',3':4,5]thiazolo[2,3-b]quinazolines and pyrazolo[2',3':4,5]thiazolo[2,3-b]quinazolines

The starting materials thiazolo[2,3-b]quinazolines (5a,b) were obtained in one pot synthesis by treating octahydroquinazoline (2) with chloroacetic acid and aromatic aldehydes. Thiazoloquinazoline (5) was reacted with CH2(CN)2/piperidine and CH2(CN)2/NaOH (CH3OH), to furnish pyrano[2',3':4,5]thiazolo[2,3-b]quinazolines (6a,b) and pyrido[2',3':4,5]thiazolo[2,3-b]quinazoline (7), respectively. Refluxing of 5a with NH2CSNH2/KOH and hydrazines in ethanol furnished the corresponding, [1,3]thiazino[4'5':4,5]thiazolo[2,3-b]quinazoline (10) and pyrazolo[3',4':4,5]thiazolo[2,3-b]quinazolines (11a,b), respectively. Antifungal activity was shown for some of the synthesized compounds.

Transformation of steroids by spores of microorganisms. I. Hydroxylation of progesterone by conidia of Aspergillus ochraceus

Conidia of Aspergillus ochraceus convert progesterone into 11alpha-hydroxyprogesterone and 6beta, 11alpha-dihydroxyprogesterone. The conversion ability does not depend on the sporulation medium. Transformation depends on the strain and on the conidia concentration. Adaptation has never been observed. Age and storage of conidia, pH, aeration-agitation, nitrogen source, metal ions, chelating agents, and metabolic activators showed no great influence within wide limits. Mercuric chloride, p-chloromercuribenzoate, NaN(3), and KCN inhibit conversion. Glucose is necessary, but can be replaced completely by d(+)-xylose, and partially by some other carbon sources. The ratio mono-/di-hydroxyprogesterone is influenced by progesterone concentration and period of incubation; also, a mutant that accumulates only monohydroxyprogesterone has been produced. Conidia of A. ochraceus also hydroxylate a variety of steroids. Spores of certain streptomycetes, phycomycetes (mucors), ascomycetes, and deuteromycetes are active. Most reactions already observed with vegetative cells have been repeated with spores. In general, spores of a particular organism effect fewer reactions than its mycelium, and fewer products accumulate.

Effect of 6-MFA, an interferon inducer obtained from fungus Aspergillus ochraceus on hepatic mixed function oxidase system in rats

Effect of 6-MFA (sixth mycelial fraction of acetone), an interferon inducer obtained from fungus A. ochraceus on hepatic mixed function oxidase system (MFO) of rat has been investigated. Treatment with 6-MFA, 100 mg/kg/day, ip for 1-5 days to adult rats inhibited significantly the different indices of MFO system, viz. hepatic cytochrome P-450, cytochrome b5 content, cytochrome c reductase, aminopyrine-N-demethylase and acetanilide hydroxylase activities. Similar treatment for 3 days in young growing rats significantly inhibited MFO system's components except acetanilide hydroxylase activity which showed marked elevation. These effects seem to be specific as in vitro experiments suggested that 6-MFA does not compete with subsdtrates nor it acts as a sponge reacting with the end product to give false inhibitory effect. It is concluded from the present study that 6-MFA like other interferon inducers depresses MFO system in rats. Its possible clinical implications are discussed.

[Ochratoxin A genotoxicity, relation to renal tumors]

Ochratoxin A (OTA) is a mycotoxin which has been implicated in Balkan Endemic Nephropathy (BEN), a disease characterized by tubulonephritis and may be involved in the high incidence of urinary tract tumors associated to BEN. The prevalence of human ochratoxicosis is being determined in Tunisia. 100% of people suffering from chronic interstitial nephropathy of unknown etiology were ochratoxin A positive. These nephropathies are similar to Balkan Endemic Nephropathy. We prove an OTA genotoxic effects in patient suffering from this kind of nephropathy. OTA-DNA adducts formation has been detected in DNA of kidney tissues (biopsy). DNA adducts which are covalent complex between OTA and DNA base (Guanine), constitute first steps of the carcinogenesis process.

[Inhibition of eight natural foods on mutagenic effect by aflatoxin B1 and extracts of fungi]

Eight natural foods were tested for their antimutagenic activities on AFB1, metabolic extracts of A. versicolor and A. ochraceus which induced mutagenic activity in TA 98 and TA 100 mutants. The tested substances were extracted repeatedly with acetone. The revertance induced by AFB1, metabolic extracts of A. versicolor and A. ochraceus were significantly decreased when the eight natural foods were added into the medium. The results showed that the eight natural foods had different degrees of anti-mutagenic effect in vitro, suggesting that anti-mutagenic substances were present in these natural foods. It is considered that these foods may be practically valuable in the chemoprophylaxis of liver cancer in men.