Effect of caffeine concentration on biomass production, caffeine degradation, and morphology of Aspergillus tamarii

Microbial metabolism of caffeine and potential applications in bioremediation

With increasing global consumption of caffeine-rich products, such as coffee, tea, and energy drinks, there is also an increase in urban and processing waste full of residual caffeine with limited disposal options. This waste caffeine has been found to leach into the surrounding environment where it poses a threat to microorganisms, insects, small animals, and entire ecosystems. Growing interest in harnessing this environmental contaminant has led to the discovery of 79 bacterial strains, eight yeast strains, and 32 fungal strains capable of metabolizing caffeine by N-demethylation and/or C-8 oxidation. Recently observed promiscuity of caffeine-degrading enzymes in vivo has opened up the possibility of engineering bacterial strains capable of producing a wide variety of caffeine derivatives from a renewable resource. These engineered strains can be used to reduce the negative environmental impact of leached caffeine-rich waste through bioremediation efforts supplemented by our increasing understanding of new techniques such as cell immobilization. Here, we compile all of the known caffeine-degrading microbial strains, discuss their metabolism and related enzymology, and investigate their potential application in bioremediation.

Occurrence, fate, persistence and remediation of caffeine: a review

Pharmaceutical and personal care products (PPCPs) have gained attention in recent years due to their continuous discharge in natural waters. Their persistence in the environment has impacted flora, fauna and human being worldwide. One of the most common PPCPs is caffeine (1, 3, 7-trimethylxanthine) which acts as a stimulant to the central nervous system in humans and is found in nature in about 60 plant species, especially in coffee, tea and cacao plants. Here we discuss the evidence with respect to caffeine occurrence, its persistence and remediation in light of increasing knowledge and the impact of caffeine on the environment. Daily intake of caffeine around the world is found to increase due to the frequent introduction of new caffeinated beverages as well as increased consumption of coffee, tea and carbonated soft drinks, which has led to increase in its concentration in water bodies including agricultural soil. The caffeine concentration in different water system, studied by various authors is also described. Diverse effects of the use of caffeine on several organisms including humans are also briefly presented. Therefore, urgent attention for the removal of caffeine and its derivatives is the need of the hour. Various methods described in literature for caffeine degradation/removal is also presented. Another widely used technique in environmental remediation is molecular imprinting (MIP); however, only few MIPs have been demonstrated for caffeine which is also discussed. Regular monitoring can be useful to control toxic effects of caffeine. Graphical abstract.

From flasks to single used bioreactor: Scale-up of solid state fermentation process for metabolites and conidia production by Trichoderma asperellum

Currently, the increasing demand of biopesticides production to replace chemical pesticides which are excessively used has made solid state fermentation (SSF) technology the need of the hour. In spite of advantages, true potential of SSF process has not been fully realized at industrial scale. A fermentation process for 6-pentyl-a-pyrone (6 PP), conidia, and lytic enzymes (cellulases, lipase, amylase) production by Trichoderma asperellum TF1 was scaled-up from 250 mL flasks and glass Raimbault column packed with 20 g of solid substrates (dry weight) to 5 Kg of solid substrate by using a new plastic single used bioreactor. For column and single used bioreactor, the fermentation was done with the application of humid air during all the process however flasks are not hermetically closed that some oxygen could flow by diffusion. T. asperellum growth was investigated using a mixture of vine shoots, jatropha cake, olive pomace and olive oil as substrate in all systems in parallel at 25 °C during 7 days. Overall, the conditions applied on the single used bioreactor resulted in the optimum 6-PP production (7.36 ± 0.37 mg g DM^-1), lipases (38.73 ± 0.21U/g DM), amylases (15.22 ± 0.13 U/g DM), and conidia production (8.55 ± 0.04 × 10⁹ conidia/g DM).

Genotoxic effect of caffeine in Yarrowia lipolytica cells deficient in DNA repair mechanisms

Caffeine is a compound that can exert physiological-beneficial effects in the organism. Nevertheless, there are controversies about its protective-antioxidant and/or its negative genotoxic effect. To abound on the analysis of the possible genotoxic/antioxidant effect of caffeine, we used as research model the yeast Yarrowia lipolytica parental strain, and mutant strains (∆rad52 and ∆ku80), which are deficient in the DNA repair mechanisms. Caffeine (5 mM) showed a cytostatic effect on all strains, but after 72 h of incubation the parental and ∆ku80 strains were able to recover of this inhibitory effect on growth, whereas ∆rad52 was unable to recover. When cells were pre-incubated with caffeine and H₂O₂ or incubated with a mixture of both agents, a higher inhibitory effect on growth of mutant strains was observed and this effect was noticeably greater for the Δrad52 strain. The toxic effect of caffeine appears to be through a mechanism of DNA damage (genotoxic effect) that involves DSB generation since, in all tested conditions, the growth of Δrad52 strain (cells deficient in HR DNA repair mechanism) was more severely affected.

Biodegradation of caffeine by whole cells of tea-derived fungi Aspergillus sydowii, Aspergillus niger and optimization for caffeine degradation

BACKGROUND

Pu-erh tea is a traditional Chinese tea and produced by natural solid-state fermentation. Several studies show that the natural microbiota influence caffeine level in pu-erh tea. Our previous research also found that the caffeine declined significantly (p < 0.05) in the fermentation, which suggested that the caffeine level could be influenced by specific strains. The purpose of this study was to isolate and identify microorganisms for caffeine degradation, and this research explored the degradation products from caffeine and optimal condition for caffeine degradation.

RESULTS

11 Fungi were isolated from pu-erh tea fermentation and 7 strains could survive in caffeine solid medium. Two superior strains were identified as Aspergillus niger NCBT110A and Aspergillus sydowii NRRL250 by molecular identification. In the substrate tests with caffeine, A. niger NCBT110A could use caffeine as a potential carbon source while glucose is absent, A. sydowii NRRL250 could degrade 600 mg/L caffeine completely in a liquid medium. During the degradation product analysis of A. sydowii NRRL250, theophylline and 3-methlxanthine were detected, and the level of theophylline and 3-methlxanthine increased significantly (p < 0.05) with the degradation of caffeine. The single factor analysis showed that the optimum conditions of caffeine degradation were 1) substrate concentration of 1200 mg/L, 2) reaction temperature at 30 °C, and 3) pH of 6. In the submerged fermentation of tea infusion by A. sydowii NRRL250, 985.1 mg/L of caffeine was degraded, and 501.2 mg/L of theophylline was produced.

CONCLUSIONS

Results from this research indicate that Aspergillus sydowii NRRL250 was an effective strain to degrade caffeine. And theophylline and 3-methlxanthine were the main caffeine degradation products.

The coffee-machine bacteriome: biodiversity and colonisation of the wasted coffee tray leach

Microbial communities are ubiquitous in both natural and artificial environments. However, microbial diversity is usually reduced under strong selection pressures, such as those present in habitats rich in recalcitrant or toxic compounds displaying antimicrobial properties. Caffeine is a natural alkaloid present in coffee, tea and soft drinks with well-known antibacterial properties. Here we present the first systematic analysis of coffee machine-associated bacteria. We sampled the coffee waste reservoir of ten different Nespresso machines and conducted a dynamic monitoring of the colonization process in a new machine. Our results reveal the existence of a varied bacterial community in all the machines sampled, and a rapid colonisation process of the coffee leach. The community developed from a pioneering pool of enterobacteria and other opportunistic taxa to a mature but still highly variable microbiome rich in coffee-adapted bacteria. The bacterial communities described here, for the first time, are potential drivers of biotechnologically relevant processes including decaffeination and bioremediation.