Kinetics of growth and caffeine demethylase production of Pseudomonas sp. in bioreactor

Abstract

The effect of various initial caffeine concentrations on growth and caffeine demethylase production by Pseudomonas sp. was studied in bioreactor. At initial concentration of 6.5 g l(-1) caffeine, Pseudomonas sp. showed a maximum specific growth rate of 0.2 h(-1), maximum degradation rate of 1.1 g h(-1), and caffeine demethylase activity of 18,762 U g CDW(-1) (CDW: cell dry weight). Caffeine degradation rate was 25 times higher in bioreactor than in shake flask. For the first time, we show highest degradation of 75 g caffeine (initial concentration 20 g l(-1)) in 120 h, suggesting that the tested strain has potential for successful bioprocess for caffeine degradation. Growth kinetics showed substrate inhibition phenomenon. Various substrate inhibition models were fitted to the kinetic data, amongst which the double-exponential (R(2) = 0.94), Luong (R(2) = 0.92), and Yano and Koga 2 (R(2) = 0.94) models were found to be the best. The Luedeking-Piret model showed that caffeine demethylase production kinetics was growth related. This is the first report on production of high levels of caffeine demethylase in batch bioreactor with faster degradation rate and high tolerance to caffeine, hence clearly suggesting that Pseudomonas sp. used in this study is a potential biocatalyst for industrial decaffeination.

Isolation and identification of caffeine-degrading bacteria from soil, coffee pulp waste and excreted coffee bean in Luwak feces

“…It was maintained on caffeine associated sucrose (CAS) agar medium and subcultured once a week to prevent the loss of its caffeine-degrading ability. Under optimal growth condition in the bioreactor, this strain was found to degrade 100% caffeine with initial caffeine concentration of 20 g L -1 (Gummadi and Santhosh 2010). This was the best strain withstanding higher concentrations of caffeine reported so far.…”

Response Surface Optimization for Decaffeination and Theophylline Production by Fusarium solani

“…Literature reports on the effect of carbon sources on caffeine degradation are inconclusive and with contradictions. The addition of sucrose, glucose and fructose were reported to enhance decaffeination by different organisms [12,32,33]. The possible reason for the differences in carbohydrate utilization by organisms of the same genera could be that the response is strain dependent.…”

“…Microbial and enzyme-based processes offer an environment friendly, cost effective, and sustainable alternative to chemical-based processes [12,13]. A great deal of work has been reported in literature regarding decaffeination using microorganisms both by bacterial cultures like Pseudomonas sp., Serratia, Rhodococcus, Klebsiella, and Leifsonia species [14][15][16][17] as well as by fungal strains such as Aspergillus, Penicillium, Trichosporon, and Fusarium sp.…”

Degradation of caffeine by Pseudomonas monteilii KRM9

“…P. putida NCIM5235 could degrade 59.9 -21.5% of the caffeine in a medium containing 7.5 -10 g/L caffeine (Dash and Gummadi, 2006) and this bacterium could degrade 100℅ of caffeine at 18 h when it was allowed to grow on a medium containing 6.4 g/L caffeine with 700 and 800 rpm aeration (Gummadi et al, 2009). It also could degrade 100% of caffeine on a medium contained 1 g/L caffeine after 15 h incubation (Gummadi and Devarai, 2010). Besides bacteria, another microorganism which also has the ability to degrade caffeine is Aspergillus tamarii V12A25.…”