The effects of a weak electric field on the growth and metabolic behavior of Enterobacter dissolvens were investigated using glucose as the sole carbon source. A direct current (DC) was applied using salt bridge electrodes and platinum electrodes. The best stimulating effects in terms of cell growth and the dehydrogenase activity (DHA) were obtained when a DC of 10mA was applied for 12 h via the platinum electrodes. In this case, the electrolysis of water was the major electrode reaction, as determined by cyclic voltammetry. The presence of the hydrogen generated a strong reductive environment and led to a reduction of NAD/NADH ratio from 7 to 3. The specific activity of dehydrogenase and glucose consumption increased 2- and 1.5-fold, respectively. The application of the DC via the platinum electrodes also led to accelerated cell death during the later stationary phase. This is possibly due to the presence of anodic intermediates including H2O2, OH• and O2•. These results provide more details for understanding the effect of a DC on E. dissolvens, a strain with potential application in the electro-remediation of PAHs contaminated soil.

Refolding of native and recombinant lysozyme was accomplished by dilution with refolding buffer containing low-concentration cetyltrimethylammonium bromide (CTAB). In both cases, the use of-cyclodextrin (β-CD) was unnecessary. Centered on the interaction between CTAB and the protein being refolded, experimental studies were conducted to investigate the effect of CTAB on the refolding yield, product distribution and the refolding kinetics. A comparative study of the artificial chaperone-assisted refolding of native and recombinant lysozyme was included to generate a more comprehensive understanding of the function of CTAB in assisting protein refolding. It was shown that the formation of CTAB-denatured lysozyme complex occurred at the beginning stage of refolding effectively inhibited the formation of aggregate, leading to an improved refolding. The dissociation of this complex occurred, when lysozyme started to fold into its native conformation catalyzed by GSSG/GSH. The use of β-CD facilitated the dissociation the CTAB-protein complex and thus increased the overall rate of lysozyme refolding. The results described by present study are also helpful for the design of surfactant and the optimization of refolding process for different proteins.

Anewmethod for determining the amount of adsorbed protein on membrane surface is developed on the basis of immunoassay using alkaline phosphotase as enzyme label and 4-nitrophenyl phosphate as substrate. Adsorption of human serum albumin (HSA) on HT Tuffryn, a kind of polysulfone microfiltration membrane, in the absence and presence of an electric field is investigated experimentally. It is shown that the adsorption of HSA on HT membrane surface is finished within 5 min and the amount of the adsorbed HSA decreases with the increase in pH but is not sensitive to salt concentration. Desorption of the adsorbed HSA from HT membrane surface can only be achieved with NaOH. Adding surfactants in HSA solution to prevent the adsorption is attempted and Tween 20 shows the best shielding function compared to polyethylene glycol 6000 and pluronic-F108. A critical concentration exists for Tween 20, below which the increase in the concentration of Tween 20 results in a corresponding reduction of adsorbed HSA. Introducing electric field into the adsorption leads to an enhanced adsorption of HSA, which appears to be a function of pH and the electric field strength.