Haloalkane hydrolysis by Rhodococcus erythropolis cells: Comparison of conventional aqueous phase dehalogenation and nonconventional gas phase dehalogenation

Biofiltration of air polluted by volatile organic compounds is now recognized by the industrial and research communities as an effective and viable alternative to standard environmental technologies. Whereas many studies have focused on solid/liquid/gas biofilters, there have been fewer reports on waste air treatment using other biological processes, especially in a solid/gas biofilter. In this study, a comparison was made of the hydrolysis of halogenated compounds (such as 1-chlorobutane) by lyophilized Rhodococcus erythropolis cells in a novel solid/ gas biofilter and in the aqueous phase. We first determined the culture conditions for the production of R. erythropolis cells with a strong dehalogenase activity. Four different media were studied and the amount of 1-chlorobutane was optimized. Next, we report the possibility to use R. erythropolis cells in a solid/gas biofilter in order to transform halogenated compounds in corresponding alcohols. The effect of experimental parameters (total flow into the biofilter, thermodynamic activity of the substrates, temperature, carbon chain length of halogenated substrates) on the activity and stability of lyophilized cells in the gas phase was determined. A critical water thermodynamic activity (aw) of 0.4 is necessary for the enzyme to become active and optimal dehalogenase activity for the lyophilized cells is obtained for an aw of 0.9. A temperature of reaction of 40jC represents the best compromise between stability and activity. Activation energy of the reaction was determined and found equal to 59.5 KJ/mol. The pH effect on the dehalogenase activity of R. erythropolis cells was also studied in the gas phase and in the aqueous phase. It was observed that pH 9.0 provided the best activity in both systems. We observed that in the aqueous phase R. erythropolis cells were less sensitive to the variation in pH than R. erythropolis cells in the gas phase. Finally, the addition of volatile Lewis base (triethylamine) in the gaseous phase and the action of the lysozyme in order to permeabilize the cells was found to be highly beneficial to the effectiveness of the biofilter

Takotsubo syndrome: voices to be heard

This paper is written from the perspective of patients who have been diagnosed with takotsubo syndrome. It seeks to understand why these patients may feel dissatisfied with the care they receive. We consider four factors: (a) takotsubo syndrome is a relatively new condition and the knowledge base about treatment is limited and not widely disseminated among clinicians; (b) the age and gender profile of the patient group; (c) the implications of the categorisation of takotsubo syndrome as ‘broken heart syndrome’ and the over-emphasis of it as a ‘psychosomatic’ condition; (d) concern that patients with takotsubo syndrome might be labelled as over-emotional, especially if they do not recover quickly. We argue that these factors contribute to patients with takotsubo syndrome feeling poorly served