Takamitsu Iida

Transformation of steroids by gel-entrapped Nocardia rhodocrous cells in organic solvent

SummaryWhole cells of Nocardia rhodocrous were immobilized by entrapment with photo-crosslinkable resin prepolymers or urethane prepolymers of either hydrophilic or hydrophobic character, and their activity in converting 3β- hydroxy-Δ5 to corresponding 3-keto-Δ4 in an appropriate organic solvent system (e.g., a water-saturated mixture of benzene and n-heptane (1∶1 by volume)) was studied. Although both hydrophilic gel-entrapped cells and hydrophobic gel-entrapped cells could transform dehydroepiandrosterone to 4-androstene-3, 17-dione, the latter showed a significantly higher activity than the former. In the cases of the oxidation of cholesterol, β-sitosterol and stigmasterol to the corresponding 3-keto-Δ4-steroids, only hydrophobic gel-entrapped cells exhibited the catalytic activity.The cells entrapped in adequate hydrophobic gels had steroid transforming activity comparable to that of the free counterparts. The operational stability was improved by the entrapment, especially in the case of the transformation of dehydroepiandrosterone. The activity of the gel-entrapped cells was found to correspond closely to the partition coefficients of substrates between the gels and the external solvent.

Continuous ethanol fermentation in molasses medium using Zymomonas mobilis immobilized in photo-crosslinkable resin gels

Abstract Zymomonas mobilis B-69 147, an ethanol-producing bacterium, was immobilized in photo-crosslinkable resin gels to form a biocatalyst system. Continuous ethanol fermentation with this immobilized Zymomonas was carried out in molasses and compared to that with immobilized yeast. As a result of operating this process for two weeks, a productivity of 60 g/l·h based on immobilized gel was obtained with improvement in the poor tolerance to salts of Zymomonas. The productivity of immobilized Z. mobilis was superior to that of immobilized yeast.

Characteristics of Zymomonas mobilis immobilized by photo-crosslinkable resin in ethanol fermentation

Abstract Zymomonas mobilis , an ethanol-producing bacterium, was immobilized in hydrophilic photo-crosslinked resin gels to form a biocatalyst. The molecular structure of the photo-crosslinkable resin could be modulated so as to minimize a disadvantage of this bacterium—poor-tolerance to salts in molasses. Characteristics of Z. mobilis immobilized by photo-crosslinkable resin gel, such as fermentability, cell growth in gel, the potential of gel materials, diffusion of materials, and salt distribution are discussed. ENTG-3800 photo-crosslinkable resin was selected as the most suitable entrapping material for Z. mobilis , especially in using molasses.