Isolation, characterization and application of theophylline-degrading Aspergillus fungi

Combinative effect of pulsed-light irradiation and solid-state fermentation on ginkgolic acids, ginkgols, ginkgolides, bilobalide, flavonoids, product quality and sensory assessment of Ginkgo biloba dark tea

Pulsed light (PL) is a prospective non-thermal technology that can improve the degradation of ginkgolic acid (GA) and retain the main bioactive compounds in Ginkgo biloba leaves (GBL). However, only using PL hasn't yet achieved the ideal effect of reducing GA. Fermentation of GBL to make ginkgo dark tea (GDT) could decrease GA. Because different microbial strains are used for fermentation, their metabolites and product quality might differ. However, there is no research on the combinative effect of PL irradiation fixation and microbial strain fermentation on main bioactive compounds and sensory assessment of GDT. In this research, first, Bacillus subtilis and Saccharomyces cerevisiae were selected as fermentation strains that can reduce GA from the five microbial strains. Next, the fresh GBL was irradiated by PL for 200 s (fluences of 0.52 J/cm2), followed by B. subtilis, S. cerevisiae, or natural fermentation to make GDT. The results showed that compared with the control (unirradiated and unfermented GBL) and the only PL irradiated GBL, the GA in GDT using PL + B. subtilis fermentation was the lowest, decreasing by 29.74%; PL + natural fermentation reduced by 24.53%. The total flavonoid content increased by 14.64% in GDT using PL + B. subtilis fermentation, whose phenolic and antioxidant levels also increased significantly. Sensory evaluation showed that the color, aroma, and taste of the tea infusion of PL + B. subtilis fermentation had the highest scores. In conclusion, the combined PL irradiation and solid-state fermentation using B. subtilis can effectively reduce GA and increase the main bioactive compounds, thus providing a new technological approach for GDT with lower GA.

Caffeine Synthesis and Its Mechanism and Application by Microbial Degradation, A Review

Caffeine is a metabolite derived from purine nucleotides, typically accounting for 2-5% of the dry weight of tea and 1-2% of the dry weight of coffee. In the tea and coffee plants, the main synthesis pathway of caffeine is a four-step sequence consisting of three methylation reactions and one nucleosidase reaction using xanthine as a precursor. In bacteria, caffeine degradation occurs mainly through the pathways of N-demethylation and C-8 oxidation. However, a study fully and systematically summarizing the metabolism and application of caffeine in microorganisms has not been established elsewhere. In the present study, we provide a review of the biosynthesis, microbial degradation, gene expression, and application of caffeine microbial degradation. The present review aims to further elaborate the mechanism of caffeine metabolism by microorganisms and explore the development prospects in this field.

Theogallin-to-Gallic-Acid Ratio as a Potential Biomarker of Pu-Erh Teas

There are two types of Pu-erh tea available on the world market: Raw and Ripe. It is not difficult to tell them apart if the Raw version is relatively young. Researchers have already developed various tools to identify Pu-erh teas. However, they are quite complicated and require advanced statistical analyses. In addition, they are characterized by different levels of accuracy. The aim of the work was to identify relationships or differences that would easily give specific results for identifying types of Pu-erh tea. The content of selected methylxanthines was determined by high-performance liquid chromatography (HPLC) on an Agilent 1200 chromatograph with a UV-VIS diode array detector. The total analysis time was 28 min. A combination of liquid chromatography and a triple quadrupole mass spectrophotometer was used to identify gallic acid and theogallin in the analyzed samples. A multivariate cluster analysis was used to compare the results for single samples, and its results were presented in horizontal hierarchical tree plots. The quantitative determination showed that theophylline is present only in Ripe Pu-erh teas. In addition, it was shown that the ratio of theogallin to gallic acid can be an effective tool to verify the authenticity of Pu-erh varieties.

Uptake, subcellular distribution and metabolism of 14C-caffeine in leafy vegetables from water

Irrigation with treated wastewater could lead to the accumulation of caffeine in agricultural fresh. Caffeine is one of the most frequently detected compounds in treated wastewater; however, little is known about its subcellular distribution and metabolism in vegetables. This study reported the uptake, subcellular distribution, and metabolism of ¹⁴C-caffeine in Chinese flowering cabbage and water spinach. The results showed that 98% of caffeine lost from solution after 768 h of cultivation. Caffeine was taken up by vegetables and most ¹⁴C-activity was accumulated in the bottom leaves. At the subcellular level, ¹⁴C-activity was mainly distributed in the organelles in root and stem cells, while in the leafy cells it was dominant in the solution. The metabolism of caffeine was investigated using LC-QTOF-MS. Caffeine underwent demethylation forming xanthine and theobromine, and mineralization to release CO₂. Approximately 40.2% of the initially applied caffeine was accumulated in Chinese flowering cabbage as the parent compound (28.3%) and metabolites (11.9%), and 50.9% of the added caffeine was mineralized to CO₂ after 768 h of exposure. The knowledge obtained herein is key to evaluating potential risks of caffeine present in treated wastewater, and the quality and safety of agricultural fresh produced by irrigation with treated wastewater.

Comparison of characteristic components in tea-leaves fermented by Aspergillus pallidofulvus PT-3, Aspergillus sesamicola PT-4 and Penicillium manginii PT-5 using LC-MS metabolomics and HPLC analysis

Microbiota influenced quality formation of ripened Pu-erh tea. To understand the effect of each tea-derived fungal strain, tea-leaves were fermented by Aspergillus pallidofulvus PT-3 (ApaPT), Aspergillus sesamicola PT-4 (AsePT) and Penicillium manginii PT-5 (PmaPT), respectively. 14 Phenolic compounds, 3 purine alkaloids, 19 free amino acids and γ-aminobutyric acid contents were determined by HPLC and amino acid analyzer analysis. Additionally, UHPLC-Q-TOF/MS method was developed for LC-MS metabolomics analysis. Multivariate statistical analyses, such as PCA and HCA, exhibited that the chemical profile of PmaPT fermentation was similar to biocidal treatment, but had significant differences with ApaPT and AsePT fermentation. The differentiated metabolites (VIP > 1, p < 0.05 and FC > 1.50 or < 0.66) and one-way ANOVA revealed the impact of three fungal strains in tea-leaves fermentation. APaPT and AsePT contributed to biosynthesis of gallic acid and several flavonoids, such as kaempferol, quercetin and myricetin in the metabolism of phenolic compounds.

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.