Hisashi Morikawa

Culture Conditions for Intracellular Lipase Production by Rhizopus chinensis and Its Immobilization within Biomass Support Particles

Acetone-dried cells of Rhizopus chinensis (with a 1,3-positional specificity lipase) were investigated for the interestierification reaction of olive oil and methyl stearate. First, the culture conditions for intracellular lipase production were examined, and then the activities of dried cells obtained from immobilization in Biomass Support Particles (BSPs) were compared with those of freely suspended cells. It was clear from cultivation of freely suspended cells that intracellular lipase activity for the interesterification reaction was enhanced sifnificantly by the presence of oleic acid, oil, and tea oil, but that the presence of glucose reduced the activity. The specific activity of dried cells within BSPs increased 7-fold compared with that obrained from freely suspended cells. The process presented here, using immobilization within BSPs, can provide cells directly as a catalyst with high activity, where cells become immobilized simply during batch operation, and no special preparation of cells is necessary. Therefore, the reaction system using dried cells immobilized within BSPs is a promising interesterifcation process for industrial applications.

Kinetic studies on the interesterification of oils and fats using dried cells of fungus

Abstract The kinetics of enzymatic interesterification of oils and fats, using acetone dried cells of Rhizopus chinensis as a lipase catalyst, have been investigated in a batch operation. To clarify the mechanism of this reaction, several models are discussed under various conditions in terms of the ratio of triglyceride (TG)/fatty acid (FA) and of the water content. First, in the reaction between olive oil and methyl stearate, the parameters involved in each model were determined by the trial-and-error method so as to make the calculated results fit with the experimental data. Then, the models were compared with the experimental data obtained from the reactions with a mixture of stearic and palmitic acid methyl esters, where the proportions of (TG)/(FA) and water content were varied. From the results, the model based on either first order kinetics or on the formation of the glyceride-enzyme complex was confirmed to fit best with the data under a wide range of reaction conditions. This suggests that the fatty acid moiety of TG seems to be exchanged through the glyceride-enzyme complex in the enzymatic interesterification of oils and fats.

Enhancement of γ-linolenic acid production by Mucor ambiguus with nonionic surfactants

Summaryγ-Linolenic acid (GLA) production by Mucor ambiguus IFO 6742, immobilised in Biomass Support Particles (BSPs), has been investigated in a fluidized-bed fermenter in the presence of nonionic surfactants. In this system, repeated batch cultivation was achieved at higher yield and productivity than by conventional methods, since microbial lipids inlcuding GLA were significantly secreted into the culture broth and/or on the surface of the cell wall.

Selective separation of γ-linolenic acid ethyl ester using y-zeolite

Abstract To highly purify γ-linolenic acid (GLA) from microbial lipids, various types of zeolites were investigated in a fixed-bed column system, where a two-step desoprtion operation mode was found to be superior in selective separation of GLA. By this system, GLA ethyl ester of 98 mol% purity was obtained from a mixture of various polysaturated and unsaturated fatty acid esters using cesium Y and methyl-, dimethyl- and ethylammonium Y zeolites.

The separation of glutathione and glutamic acid using a simulated moving-bed adsorber system

Abstract Glutathione (GSH) and glutamic acid (Glu) were continuously separated using a simulated moving-bed adsorber system. In this system, a specially-designed multi-port rotary valve was used to move the adsorbent particles, and its rotation speed and the liquid flow rate in the adsorber were controlled by a personal computer. Under the optimal conditions for the simulated moving-bed adsorber, both the purity and the yield coefficient of GSH in the raffinate stream at a steady state reached around 99%, and the concentration of GSH and the production of GSH for the amount of adsorbent used were greater by as much as ten times and eighteen times than for the conventional batch operation. The adsorption isotherms of GSH and Glu, which were non-linear and concetration-dependent, wre well expressed using several parameters, and also the courses of GSH and Glu concentrations in transient changes to the steady-state condition could be predicted well by the intermittent moving-bed model.

Cloning of a gene for S-adenosylmethionine synthesis in Saccharomyces cerevisiae

SummaryThe gene for ethionine resistance was isolated, and its phenotypic characteristics were investigated. The cells transformed with this gene showed strong resistance to DL-ethionine, and S-adenosylmethionine (SAM) was remarkably accumulated within the cells. Judging from the restriction map of this gene, it suggests that the gene is not the gene SAM1 but SAM2.