Biocatalysts assessing effectiveness

The draft-tube airlift bioreactor was studied using water-in-kerosene microemulsions [263], The effect of draft tube area vs. the top-section area on various parameters was studied. The effect of gas flow rates on recirculation and gas carry over due to incomplete gas disengagement were studied [264], Additionally, the effect of riser to downcomer volume was also studied. The effect of W/O ratio and viscosity was tested on gas hold-up and mass transfer coefficient [265], One limitation of these studies was the use of plain water as the aqueous phase in the cold model. The absence of biocatalyst or any fermentation broth from the experiments makes these results of little value. The effect of the parameters studied will greatly depend on the change in viscosity, hold-up, phase distribution caused due to the presence of biocatalyst, such as IGTS8, due to production of biosurfactants, etc., by the biocatalyst. Thus, further work including biocatalyst is necessary to truly assess the utility of the draft-tube airlift bioreactor for biodesulfurization. 

To assess the impact of IDR on enzyme kinetics, the value of intrinsic kinetics (V" and K) and mass transfer (Deff) parameters must be evaluated. Several strategies have been proposed to approximate the value of the intrinsic kinetic parameters. A reliable experimental procedure is the one proposed by Benaiges et al. (1986) which is basically based on comminuting the support to obtain particles so small than IDR becomes negligible (very low Osp see Eq. 4.54). Kinetic parameters can be determined then with that comminuted biocatalyst to have an estimate on the intrinsic values. Effectiveness factor can be approached then to the ratio of initial rates for the intact and comminuted biocatalyst (Kobayashi and Laidler 1973). An obvious drawback of this approach is that not always a biocatalyst particle small enough can be obtained to be free of IDR (effectiveness factor = 1). If a smooth correlation exists between effectiveness factor and particle size, extrapolation to size zero could give an approximate value and intrinsic kinetic parameters can be... 

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