Tadashi Funada

Concentration of docosahexaenoic acid in glyceride by hydrolysis of fish oil withcandida cylindracea lipase

In an attempt to concentrate the content of DHA (docosahexaenoic acid) in a glyceride mixture containing triglyceride, diglyceride and monoglyceride, fish oil was hydrolyzed with six kinds of microbial lipase. After the hydrolysis, free fatty acid was removed and fatty acid components of the glyceride mixtures were analyzed. When the hydrolysis withCandida cylindracea lipase was 70% complete, the DHA content in the glyceride mixture was three times more than that in the original fish oil. The EPA (eicosapentaenoic acid) content became almost 70% of the original fish oil. Hydrolysis with other lipases did not result in an increase in the DHA content in the glyceride mixtures. Hydrolysis of DHA-rich tuna oil (DHA content is about 25%) withCandida cylindracea lipase resulted in 53% DHA in the glyceride mixture. The EPA content, however, remained close to that of the original tuna oil. In this report, the acyl chain specificity of lipases is evaluated in terms of hydrolysis resistant value (HRV). HRV is the ratio between the DHA contents in the glyceride mixture of hydrolyzed oil and original oil. HRV clearly indicates differences in hydrolysis between DHA and other fatty acids (e.g., saturated and monoenoic acids).

Triglyceride specificity ofCandida cylindracea lipase: Effect of docosahexaenoic acid on resistance of triglyceride to lipase

Tuna oil was hydrolyzed withCandida cylindracea lipase. After 70% hydrolysis of the oil, the docosahexaenoic acid (DHA) content in the glyceride mixture [a mixture of TG (triglyceride), DG (diglyceride) and MG (monoglyceride)] was twice that of the original oil. DHA-rich TG and DG were observed, but DHA-rich MG was absent.C. cylin-dracea lipase seemed to have a “triglyceride specificity,” and it favors TG without DHA over TG containing DHA. In accordance with this hypothesis, TG containing a mixture of oleic acid (OA) and DHA was synthesized and then hydrolyzed withC. cylindracea lipase. TGs in the hydrolysis product were fractionated and analyzed quantitatively by high-performance liquid chromatography. Four kinds of TGs were obtained. TG with three molecules of OA was hydrolyzed most easily. Increasing the DHA content of TG resulted in less hydrolysis of TG. The results suggested thatC. cylindracea lipase had a TG specificity for the whole structure of TG in preference to the individual ester bonds; OA coexisting with DHA in TG was resistant toC. cylindracea lipase due to the TG structure.

Synthesis of docosahexaenoic acid-rich triglyceride with immobilizedChromobacterium viscosum lipase

Docosahexaenoic acid (DHA) in the free fatty acid (FFA) derived from enzymically hydrolyzed tuna oil was concentrated by partial titration and precipitation of other FFA as sodium salts with acetone. A triglyceride containing up to 46.2% DHA was synthesized from the DHA-rich glyceride mixture and FFA by use of an immobilizedChromobacterium viscosum lipase.

On Σ -Π separability in the electronic transitions of conjugated molecules

Abstract The π → π ∗ transitions to triplets are shown to be independent of the σ → σ ∗ transitions if the zero differential overlaps are assumed between the pi- and sigma-orbitals. For the singlet transitions, however, Σ—Π coupling does not vanish, and its inclusion is explicitly depicted.

Studies on the Stabilization of Enzyme. II.

Glycerol poly (oxyethylene) ether (GPEE) was found to effectively stabilize Candida cylindracea lipase in an aqueous solution (100U/ml) at 50°C. That is, this lipase became thermally stable in the presence of GPEE. Polyoxyethyleneglycol (PEG) and polypropyleneglycol (PPG) were also tested as stabilizing agents of this lipase in an aqueous solution and found to be effective.The relationship between the amount of additives in the lipase solution and their stabilizing extent was complicated. GPEE stabilized the lipase in proportion to its concentration and PEG brought about maximum stabilization at a concentration of 2.5mmol/20ml of solution. But stabilization became progressively less with increasing amount of PEG.Consequently, each additive is considered to have indivisual mechanism for imparting stability to a lipase solution.