Enhanced biodegradation of caffeine by Pseudomonas sp. using response surface methodology

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.

Simultaneous Optimization of Activity and Stability of Xylose Reductase from D. nepalensis NCYC 3413 Using Statistical Experimental Design

BACKGROUND

Physical parameters like pH and temperature play a major role in the design of an industrial enzymatic process. Enzyme stability and activity are greatly influenced by these parameters; hence optimization and control of these parameters becomes a key point in determining the economic feasibility of the process.

OBJECTIVE

This study was taken up with the objective to optimize physical parameters for maximum stability and activity of xylose reductase from D. nepalensis NCYC 3413 through separate and simultaneous optimization studies and comparison thereof.

METHODS

Effects of pH and temperature on the activity and stability of xylose reductase from Debaryomyces nepalensis NCYC 3413 were investigated by enzyme assays and independent variables were optimised using surface response methodology. Enzyme activity and stability were optimised separately and concurrently to decipher the appropriate conditions.

RESULTS

Optimized conditions of pH and temperature for xylose reductase activity were determined to be 7.1 and 27 °C respectively, with predicted responses of specific activity (72.3 U/mg) and half-life time (566 min). The experimental values (specific activity 50.2 U/mg, half-life time 818 min) were on par with predicted values indicating the significance of the model.

CONCLUSION

Simultaneous optimization of xylose reductase activity and stability using statistical methods is effective as compared to optimisation of the parameters separately.

Caffeine in surface and wastewaters in Barbados, West Indies

Caffeine, a purine alkaloid drug, has been recognized as a contaminant of water bodies in various climatic regions, however, these environmental caffeine concentrations are the first to be reported in the tropical Caribbean. The major objective of this study was to develop an improved method to extract caffeine from surface and wastewaters in the warm Caribbean environment and measure caffeine concentrations in highly populated areas in Barbados. Caffeine was extracted from water via solid phase extraction (SPE); the acidified water samples were loaded onto C-18 cartridges and eluted with pure chloroform. The extracted caffeine was quantified using gas chromatography - mass spectroscopy - multiple reaction monitoring (GC-MS/MS-MRM). Method detection limits of 0.2 ng L⁻¹ from 1 L water samples were achieved. Caffeine was detected in all environmental water samples investigated. The concentrations of caffeine in surface waters were detected in the range 0.1 - 6.9 μg L⁻¹. The two wastewater treatment plants, primary and secondary treatment systems, significantly differed in their ability to eliminate caffeine in the raw sewage (38% and 99% caffeine removal efficiencies respectively). Thus, it may be essential to employ secondary treatment to effectively remove caffeine from wastewater systems in Barbados. Caffeine in water bodies are principally attributed to anthropogenic sources as caffeine-producing plants are not commonly grown on the island of Barbados. The study also shows the recalcitrance of caffeine to hydrolytic degradation.

Optimization of protein production by Micrococcus luteus for exploring pollutant-degrading uncultured bacteria

The screening of pollutant-degrading bacteria are limited due to most of bacteria in the natural environment cannot be cultivated. For the purpose of resuscitating and stimulating "viable but non-culturable" (VBNC) or uncultured bacteria, Micrococcus luteus proteins are more convenient and cost-effective than purified resuscitation-promoting factor (Rpf) protein. In this study, medium composition and culture conditions were optimized by using statistical experimental design and analysis to enhance protein production by M. luteus. The most important variables influencing protein production were determined using the Plackett-Burman design (PBD) and then central composite design (CCD) was adopted to optimize medium composition and culture conditions to achieve maximum protein yield. Results showed that the maximum protein yield of 25.13 mg/L (vs. 25.66 mg/L predicted) was obtained when the mineral solution, Lithium L-lactate, initial pH and incubation time were set at 1.5 ml/L, 8.75 g/L, 7.5 and 48 h, respectively. The predicated values calculated with the model were very close to the experimental values. Protein production was obviously increased with optimization fitting well with the observed fluorescence intensity. These results verified the feasibility and accuracy of this optimization strategy. This study provides promising information for exploring highly desirable pollutant-degrading microorganisms.

Physiology, biochemistry and possible applications of microbial caffeine degradation

Caffeine, a purine alkaloid is a constituent of widely consumed beverages. The scientific evidence which has proved the harm of this alkaloid has paved the way for innumerable research in the area of caffeine degradation. In addition to this, the fact that the by-products of the coffee and tea industry pollute the environment has called for the need of decaffeinating coffee and tea industry's by-products. Though physical and chemical methods for decaffeination are available, the lack of specificity for removal of caffeine in these techniques and their non-eco-friendly nature has opened the area of microbial and enzymatic degradation of caffeine. Another important application of microbial caffeine degradation apart from its advantages like specificity, eco-friendliness and cost-effectiveness is the fact that this process will enable the production of industrially and medically useful components of the caffeine degradation pathway like theobromine and theophylline. This is a comprehensive review which mainly focuses on caffeine degradation, large-scale degradation of the same and its applications in the industrial world.