Isolation and characterisation of theobromine-degrading filamentous fungi

Biotransformation of Patchouli Alcohol by Cladosporium cladosporioides and the Anti-Influenza Virus Activities of Biotransformation Products

The biotransformation of patchouli alcohol by Cladosporium cladosporioides afforded 31 products, including 21 new ones (1-3, 5, 6, 8-14, and 17-25). Their structures were determined by extensive spectroscopic data analysis (1H and 13C NMR, HSQC, HMBC, 1H-1H COSY, ROESY, and HRESIMS), and the absolute configuration of compounds 1, 2, 8, 9, and 17 was determined by single-crystal X-ray diffraction using Cu Kα radiation. Structurally, compounds 21-24 were patchoulol-type norsesquiterpenoids without Me-12. Among them, a Δ3(4) double bond existed in compounds 21 and 22; a three-membered ring was formed between C-4, C-5, and C-6 in compound 23; an epoxy moiety appeared between C-3 and C-4 in compound 24. Furthermore, the biotransformation products 9, 10, 12, and 25 showed potent anti-influenza virus activity with EC50 values of 2.11, 7.94, 20.87, and 3.45 μM, respectively.

Cocoa-associated filamentous fungi for the biocontrol of aflatoxigenic Aspergillus flavus

Aflatoxin and other mycotoxin contamination are major threats to global food security and present an urgent need to secure the global food crop against spoilage by mycotoxigenic fungi. Cocoa material is noted for naturally low aflatoxin contamination. This study was designed to assess the potential for harnessing cocoa-associated filamentous fungi for the biocontrol of aflatoxigenic Aspergillus flavus. The candidate fungi were isolated from fermented cocoa beans collected from four cocoa-growing areas in Ghana. Molecular characterization included Internal Transcribed Spacer (ITS)-sequencing for identification and polymer chain reaction (PCR) to determine mating type. Effects of the candidate isolates on growth and aflatoxin-production by an aflatoxigenic A. flavus isolate (BANGA1) were assessed. Aflatoxin production was monitored by UV fluorescence and quantified by enzyme-linked immunosorbent assay (ELISA). Thirty-six filamentous fungi were cultured and identified as Aspergillus, Cladosporium, Lichtheimia, or Trichoderma spp. isolates. The isolates generally interacted negatively with BANGA1 growth and aflatoxin production. The Aspergillus niger and Aspergillus aculeatus biocontrol candidates showed the strongest colony antagonism (54%-94%) and reduction in aflatoxin production (12%-50%) on agar. In broth, the A. niger isolates reduced aflatoxin production by up to 97%. Metabolites from the A. niger isolates showed the strongest inhibition of growth by BANGA1 and inhibited aflatoxin production. Four of the candidate isolates belonged to the MAT1-1 mating type and 12 identified as MAT1-2. This may be indicative of the potential for genetic recombination events between fungi in the field, a finding which is particularly relevant to the risk posed by A. flavus biocontrol measures that rely on atoxigenic A. flavus strains.

3-Methylxanthine production through biodegradation of theobromine by Aspergillus sydowii PT-2

Background

Methylxanthines, including caffeine, theobromine and theophylline, are natural and synthetic compounds in tea, which could be metabolized by certain kinds of bacteria and fungi. Previous studies confirmed that several microbial isolates from Pu-erh tea could degrade and convert caffeine and theophylline. We speculated that these candidate isolates also could degrade and convert theobromine through N-demethylation and oxidation. In this study, seven tea-derived fungal strains were inoculated into various theobromine agar medias and theobromine liquid mediums to assess their capacity in theobromine utilization. Related metabolites with theobromine degradation were detected by using HPLC in the liquid culture to investigate their potential application in the production of 3-methylxanthine.

Results

Based on theobromine utilization capacity, Aspergillus niger PT-1, Aspergillus sydowii PT-2, Aspergillus ustus PT-6 and Aspergillus tamarii PT-7 have demonstrated the potential for theobromine biodegradation. Particularly, A. sydowii PT-2 and A. tamarii PT-7 could degrade theobromine significantly (p < 0.05) in all given liquid mediums. 3,7-Dimethyluric acid, 3-methylxanthine, 7-methylxanthine, 3-methyluric acid, xanthine, and uric acid were detected in A. sydowii PT-2 and A. tamarii PT-7 culture, respectively, which confirmed the existence of N-demethylation and oxidation in theobromine catabolism. 3-Methylxanthine was common and main demethylated metabolite of theobromine in the liquid culture. 3-Methylxanthine in A. sydowii PT-2 culture showed a linear relation with initial theobromine concentrations that 177.12 ± 14.06 mg/L 3-methylxanthine was accumulated in TLM-S with 300 mg/L theobromine. Additionally, pH at 5 and metal ion of Fe²⁺ promoted 3-methylxanthine production significantly (p < 0.05).

Conclusions

This study is the first to confirm that A. sydowii PT-2 and A. tamarii PT-7 degrade theobromine through N-demethylation and oxidation, respectively. A. sydowii PT-2 showed the potential application in 3-methylxanthine production with theobromine as feedstock through the N-demethylation at N-7 position.

Nutritional value and safety of animal feed supplemented with Talaromyces verruculosus-treated cocoa pod husks

Theobromine exerts deleterious effects on animal physiology. Removal of theobromine from the millions of metric tons of cocoa pod husks (CPH) discarded annually could allow for the production of cheap, CPH-based animal feed. The aim of this study was to evaluate safety and nutritional value of bio-detheobrominated CPH in Sprague–Dawley rats. Theobromine was removed from CPH by treatment with an isolate of Talaromyces verruculosus (TvTD). Substituted feeds containing CPH were formulated by replacing 30% or 50% of the maize content of regular rat feed with TvTD-treated or inactivated TvTD-treated CPH. Feeding groups included control groups without or with theobromine administration. Effects of the feed formulations on water and feed intake, weight gain, blood biochemistry and organ-specific toxicity were assessed. Rats ingesting theobromine in inactivated TvTD-treated CPH-based diet or by oral gavage variably exhibited marked deleterious effects, mainly evident in body weight, thymus wet weight and tissue histology. In contrast, substitution with TvTD-treated CPH caused significant increase in body weight. Substitution at 30% did not cause mortality or organ-specific toxicity with reference to the testes, kidneys, spleen or liver, unlike substitution at 50%. The data demonstrate that detheobrominated CPH may safely replace up to 30% of maize in animal feed formulations.

Isolation, characterization and application of theophylline-degrading Aspergillus fungi

Background

Caffeine, theobromine and theophylline are main purine alkaloid in tea. Theophylline is the downstream metabolite and it remains at a very low level in Camellia sinensis. In our previous study, Aspergillus sydowii could convert caffeine into theophylline in solid-state fermentation of pu-erh tea through N-demethylation. In this study, tea-derived fungi caused theophylline degradation in the solid-state fermentation. The purpose of this study is identify and isolate theophylline-degrading fungi and investigate their application in production of methylxanthines with theophylline as feedstock through microbial conversion.

Results

Seven tea-derived fungi were collected and identified by ITS, β-tubulin and calmodulin gene sequences, Aspergillus ustus, Aspergillus tamarii, Aspergillus niger and A. sydowii associated with solid-state fermentation of pu-erh tea have shown ability to degrade theophylline in liquid culture. Particularly, A. ustus and A. tamarii could degrade theophylline highly significantly (p < 0.01). 1,3-dimethyluric acid, 3-methylxanthine, 3-methyluric acid, xanthine and uric acid were detected consecutively by HPLC in A. ustus and A. tamarii, respectively. The data from absolute quantification analysis suggested that 3-methylxanthine and xanthine were the main degraded metabolites in A. ustus and A. tamarii, respectively. 129.48 ± 5.81 mg/L of 3-methylxanthine and 159.11 ± 10.8 mg/L of xanthine were produced by A. ustus and A. tamarii in 300 mg/L of theophylline liquid medium, respectively.

Conclusions

For the first time, we confirmed that isolated A. ustus, A. tamarii degrade theophylline through N-demethylation and oxidation. We were able to biologically produce 3-methylxanthine and xanthine efficiently from theophylline through a new microbial synthesis platform with A. ustus and A. tamarii as appropriate starter strains.

LC-MS/MS-based metabolomic analysis of caffeine-degrading fungus Aspergillus sydowii during tea fermentation

Natural microorganisms involved in solid-state fermentation (SSF) of Pu-erh tea have a significant impact on its chemical components. Aspergillus sydowii is a fungus with a high caffeine-degrading capacity. In this work, A. sydowii was inoculated into sun-dried green tea leaves for SSF. Metabolomic analysis was carried out by using UPLC-QTOF-MS method, and caffeine and related demethylated products were determined by HPLC. The results showed that A. sydowii had a significant (P < 0.05) impact on amino acids, carbohydrates, flavonoids, and caffeine metabolism. Moreover, A. sydowii could promote the production of ketoprofen, baclofen, and tolbutamide. Along with caffeine degradation, theophylline, 3-methylxanthine, 1,7-dimethylxanthine, 1-methylxanthine, and 7-methylxanthine were increased significantly (P < 0.05) during inoculated fermentation, which showed that demethylation was the main pathway of caffeine degradation in A. sydowii secondary metabolism. The absolute quantification analysis showed that caffeine could be demethylated and converted to theophylline and 3-methylxanthine. Particularly, about 93.24% of degraded caffeine was converted to theophylline, 27.92 mg/g of theophylline was produced after fermentation. PRACTICAL APPLICATION: Aspergillus sydowii could cause caffeine degradation in Pu-erh tea solid-state fermentation and produce theophylline through the demethylation route. Using a starter strain to ferment tea leaves offers a more controllable, reproducible, and highly productive alternative for the biosynthesis of theophylline.

Production of theophylline via aerobic fermentation of pu-erh tea using tea-derived fungi

Background

Caffeine is one of the most abundant methylxanthines in tea, and it remains stable in processing of general teas. In the secondary metabolism of microorganism, theophylline is the main conversion product in caffeine catabolism through demethylation. Microorganisms, involved in the solid-state fermentation of pu-erh tea, have a certain impact on caffeine level. Inoculating an appropriate starter strain that is able to convert caffeine to theophylline would be an alternative way to obtain theophylline in tea. The purpose of this study was to isolate and identify the effective strain converting caffeine to theophylline in pu-erh tea, and discuss the optimal conditions for theophylline production.

Results

Caffeine content was decreased significantly (p < 0.05) and theophylline content was increased significantly (p < 0.05) during the aerobic fermentation of pu-erh tea. Five dominant fungi were isolated from the aerobic fermentation and identified as Aspergillus niger, Aspergillus sydowii, Aspergillus pallidofulvus, Aspergillus sesamicola and Penicillium mangini, respectively. Especially, A. pallidofulvus, A. sesamicola and P. mangini were detected in pu-erh tea for the first time. All isolates except A. sydowii TET-2, enhanced caffeine content and had no significant influence on theophylline content. In the aerobic fermentation of A. sydowii TET-2, 28.8 mg/g of caffeine was degraded, 93.18% of degraded caffeine was converted to theophylline, and 24.60 mg/g of theophylline was produced. A. sydowii PET-2 could convert caffeine to theophylline significantly, and had application potential in the production of theophylline. The optimum conditions of theophylline production in the aerobic fermentation were 1) initial moisture content of 35% (w/w), 2) inoculation quantity of 8%, and 3) incubation temperature at 35 °C.

Conclusions

For the first time, we find that A. sydowii PET-2 could convert caffeine to theophylline, and has the potential value in theophylline production through aerobic fermentation.

Bio-detheobromination of cocoa pod husks: reduction of ochratoxin A content without change in nutrient profile

Background

Utilization of cocoa pod husks (CPH) in animal feed is hindered by the presence of theobromine, which is variably toxic to animals. Treatment of this agro-waste to remove theobromine, while preserving its nutrient content, would allow beneficial use of the millions of metric tonnes discarded annually. The aim of this study was to assess the suitability of selected theobromine-degrading filamentous fungi for use as bio-tools in degradation of theobromine in CPH.

Results

The candidate fungi assessed in this study were an Aspergillus niger (AnTD) and three Talaromyces spp. (TmTD-1, TmTD-2, TvTD) isolates. All the fungi eliminated CPH theobromine, 0.15% w/w starting concentration, within 7 days of start of treatment, and were capable of degrading caffeine and theophylline. The fungi decreased CPH ochratoxin A content by 31–74%. Pectin was not detectable in fungus-treated CPH whereas parameters assessed for proximate composition were not affected.

Conclusions

The data provide ample evidence that the four isolates can be applied to CPH for the purpose of eliminating theobromine and decreasing ochratoxin A content without affecting nutrient profile. Comparatively, Talaromyces verruculosus TvTD was considered as most suitable for use as a bio-tool in detheobromination of CPH for animal feed.