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Optically active alcohols are important building blocks as versatile chiral synthons for asymmetric syntheses of pharmaceuticals and agrochemicals. The aim of this paper is to efficiently prepare chiral 2‐pentanol by means of microorganisms. The gene of dihydroxyacetone reductase (EC 1.1.1.6) from a methylotrophic yeast, Hansenula ofunaensis,was cloned and chiral 2‐pentanol was produced by the recombinant Escherichia coliharboring the gene. The gene encoding the enzyme was cloned from an H. ofunaensisgenomic library. In the deduced amino acid sequence of 364 residues, the NAD(H) binding motif and the cysteine residues that correspond to the cysteine ligands in the zinc atom were conserved, as they are in alcohol dehydrogenases from other origins. Dihydroxyacetone reductase was similar to alcohol dehydrogenases of prokaryotes. For the production of chiral compounds, an E. coliHB101 strain was transformed. The H. ofunaensisgene product, dihydroxyacetone reductase, catalyzed the NAD+‐dependent oxidation of 2‐pentanol to 2‐pentanone as well as the corresponding reverse reactions, showing specificity towards the secondary alcohol in (R)‐configuration. From 100 mM 2‐pentanone, (R)‐2‐pentanol (98 mM, > 99.9 % enantiometric excess, e.e.) was obtained in a 30‐min reaction with resting cells of the E.coliHB101 strain harboring the expression plasmid, pSG‐HOD1, which possesses the genes of both dihydroxyacetone reductase and glucose dehydrogenase as an NADH reproducing system. The stereospecificity changed during the reduction, depending on the pH. E.coliHB101 was also transformed by the expression plasmid, pSE‐HOD4, in which the gene of glucose dehydrogenase was removed from pSG‐HOD1, and designated as E.coliHB101 (pSE‐HOD4). E.coliHB101 (pSE‐HOD4) oxidized only (R)‐2‐pentanol in 100 mM of the racemate (R:S= 52:48), and the reaction medium was enriched with (S)‐2‐pentanol (48 mM, 98 % e.e.) after 30 min of incubation. The reaction was sufficiently promoted without the other additives. E.colitransformants expressing the gene of this enzyme could be particularly advantageous to the production of optically active 2‐pentanol.

The strength of the CO2hydrate membrane that forms at the interface between liquid CO2and artificial sea water at 40-45 MPa was measured with Du-Nouy type surface tension meter. At low temperatures with a subcooling greater than 5 K, the membrane strength, initially abut 0.1 Nm, decreased with increasing temperature. However, it increased sharply and reached a peak of about 0.9 Nm just below the dissociation temperature and abruptly drops to zero at the dissociation temperature. This abnormal tendency of the membrane strength was previously observed by the authors in an experiment with fresh water. The temperature of the abnormality, however, shifts to lower temperatures and the peak decreases with increasing salinity. This new phenomenon could exert major influences on the various CO2ocean sequestration methods that have been proposed to mitigate global warming. It can be explained in terms of a model in which the dissociation process of hydrate that occurs near the dissociation temperature enhances the diffusion of water molecules in the hydrate membrane and makes the membrane thicker.