Hideharu Yagi

REFOLDING OF ENZYMES IN A FED-BATCH OPERATION

Abstract Denatured and fully reduced lysozyme and ribonuclease A were refolded in batch and also in fed-batch operation. In fed-batch refolding of lysozyme, denatured lysozyme was gradually added into refolding buffers containing urea in the concentration range from 1.0 to 2.0 mol/l. The recoveries of the lysozyme activity in a fed-batch operation were higher than those in a batch operation. In the case of ribonuclease A, high recoveries were obtained in both batch and fed-batch operations. The recovery of the enzyme activity in a fed-batch system was estimated from the values of the recovery in a batch operation.

SEMIBATCH PRECIPITATION ACCOMPANYING GAS-LIQUID REACTION

To obtain large particles of insoluble product by precipitation accompanying a gas-liquid reaction, a sparged stirred vessel was operated continuously for the gaseous and liquid reactants but batchwise for the product particles. Except at the beginning of run, most particles formed floes. With increasing concentration of product particles, the average size of floes increased for CaC03 but remained unchanged or decreased slightly for SrCO3 and BaC03The effect of agitation on the floc size was significant for CaC03 but scarcely observed for SrC03 and BaC03 The mass per unit volume of sedimented floes of the three species increased with increasing concentration of product particles, and under the same conditions, they decreased in the following order: CaC03 SrC03 BaC03

Gas absorption into a slurry accompanied by chemical reaction with solute from sparingly soluble particles

Abstract A model has been developed which represents gas absorption into a slurry accompanied by chemical reaction with solute from sparingly soluble fine particles. The rate of absorption into a slurry seemed to be higher than that into a saturated solution containing no reactive particles, as reported previously by others; but our theoretical estimates disagreed with previous results, especially under conditions of instantaneous reaction. A characteristic length determined geometrically by the size and concentration of the particles is a factor in estimating the effect of particle dissolution on the rate of gas absorption, but the mass transfer coefficient for particle dissolution need not be known.

CHEMICAL ABSORPTION OF CO2 AND SO2 INTO Ca(OH) 2 SLURRY

Chemical absorption of CO2 and SO22 as single gases and as a mixture into slurries of Ca(OH) 2 was studied in a stirred vessel with a flat gas-liquid interface. In the case of CO2, the reaction product interrupted the subsequent gas absorption in the absence of a surface active agent. With single gases, the enhancement factor for SO2 was much larger than that for CO2, though both were larger than that into saturated solution. With the mixed gases, the enhancement factor for S02 was almost equal to that for the single gas absorption, but for CO2 it was only slightly larger than that into the saturated solution

Separation of papain and dextran of similar molecular weights by ultrafiltration

Abstract Ultrafiltration, a useful technique in biological process, is unsuitable for the separation of solutes of similar molecular weights. If the sizes of the solutes are changeable, however, their separation may be possible. Salting in and salting out result from the change of state of a solute with the concentration of coexisting salt. The application of these phenomena to modification of the characteristics of ultrafiltration was examined. The ultrafiltration of papain (MW 23,400) and dextran (MW 19,600) as single solutes and as a mixture was carried out in a stirred-type ultrafiltration cell with a membrane having a molecular weight cut-off of 100,000. With single solutes, the ultrafiltration characteristics of papain and dextran were different, even when their concentrations were lower than their solubilities; the rejection coefficients for papain were much larger than for dextran. In the ultrafiltration of the mixture at a salt concentration of 25 w/w%, not only papain but a part of the dextran was retained in the retentate solution. At a salt concentration of 8 w/w%, however, dextran was deriven through with the permeate solution but the rejection coefficient for papain was high. Thus, in spite of their similar molecular weights, papain and dextran are separable by ultrafiltration by changing their sizes in the solution.

Enrichment of an amino acid by micellar-enhanced ultrafiltration

Abstract It is difficult to enrich low molecular weight solutes by membrane processes with sufficient speed under low applied pressure. However, combination of a solute with micelles of a surfactant enables enrichment of the solute into the retentate solution by ultrafiltration. The micellar-enhanced ultrafiltration of an amino acid, l -tryptophan, was carried out in a batch-stirred cell. The characteristics of the ultrafiltration of the micelles were examined with respect to the permeation flux and micelle rejection. As the concentration of the micelle-forming substance, cetylpyridinium chloride monohydrate (CPC; MW 358), in the retentate solution increased, the permeation flux decreased but the concentration in the permeate solution was limited. The effect of membrane molecular weight cut-off (MWCO) on permeation flux was obvious at low CPC concentrations but only slight at high concentrations. l -Tryptophan (MW 204) combined with CPC micelles to be retained by membranes of MWCO 20,000 as well as MWCO 10,000; there was no difference in rejection between the two membranes. The rejection coefficient was estimated as a function of the solubilization constant and the micelle concentration. The rejection coefficient increased with increasing CPC concentration but too high CPC concentrations resulted in the leakage of CPC into the permeate solution.