engleski

Biooxidation kinetics in reaction systems of low water activity

Kinetics of D-glucose and S-sorbitol oxidation catalised by biocatalytic system of Gluconobacter suboxydans S-22 in reaction media of low water activity werw studed. The shake flask cultivation experiments at different temperatures were perfomed aplly reaction systems with intact and designated microbial cells suspended in sterile water solutions of different D-glucose and D-sorbitol concentrations. Values of input parametars adequaly reflected on experimental results. The increase in substrate concentrations caused an adequate decrease of volumetric oxygen transfer rate coefficient (Kla). Specific biocatalytic activity of washed whole intact cells was much higher than that of corresponding amount of disintegrated cells, only in the substance concentration range below 500 g/L. In general, specific biocatalytic activites were decreasing with increasing substrate concentration. However, the fall down of activity of intact cells as a function of substrate concentration appeard to be of sigmoidal form, while that of disrupted cells showed to be appoximately linear. A lower temperature (30oC) was more convinient for reaction systems of lower substrate concentration(100 g/L), while a higher temperature (37oC) showed to be more favourable for reaction systems of higher substrate concentrations.Data agree expetation, if taking into account findings of other (1) for other reaction systems.Based on the obtained results and our previous observation (2), it could be concluded that mass transfer phenomena play an important role in biooxidation kinetics.Findings of this work support our previous observation and suggest the application of higher biooxidation temperature, in cases when water activity in reaction systems falls down below 0.4 (e.g. when applyng high yielding prolonged fed batch culture or two-compartment fed bach culture).

biooxidation kinetics; D- glucose

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