As a n-6 essential fatty acid, γ-linolenic acid (GLA) has been shown to be more effective than linoleic acid. Its effects cover anti-atherosclerosis including hypocholesterolic and anti-thrombogenic effect, anti-cancer, higher alcohol oxidation, anti-inflammatory effect and others. These effects are generally attributed to by-passing Δ6-desaturase reaction. Using some species in genus Mortierella, lipid accumulative fungi, attempt at increase in lipid and GLA productivity has been made changing carbon and nitrogen source, pH, temperature and others. Decane as carbon source resulted in higher polar lipid content in spite of lower growth than glucose. Cultivation at higher glucose concentration (>100 g/L), originally intended to get higher cell mass per unit volume of culture medium, resulted in higher lipid content. The optimum culture conditions for lipid accumulation were lower both in pH and temperature than those for growth, which lead to our proposal of 2 tanks continuous system to separate growth from lipid accumulation phase. The maximum lipid productivity of 1.1 g/L·h and GLA productivity of 106 mg/L·h were obtained in a continuous operation at 0.15-1 of dilution rate and 100 g/L of feed glucose concentration.
Mycelia of a fungus Mortierella alpina 1 S-4, which was isolated from soil, and the mutants derived from it were found to be new and rich sources of C20 polyunsaturated fatty acids (PUFAs) of pharmacological and dietary importance. M alpina 1 S-4 produced a unique triacylglycerol oil with high ω 6 PUFA content. The mycelial content of arachidonic acid reached 274 mg/g dry mycelia (4.3 g/L) on cultivation of the fungus in a medium containing glucose and yeast extract. The value accounted nearly 70 % of the total fatty acids in the extracted oil. The same fungus produced dihomo-γ-linolenic acid (DGLA, 2.17 g/L) when grown with sesamin, a specific inhibitor of Δ5 desaturase. A mutant defective in 5 desaturase also produced DGLA (4.1 g/L). Another mutant which is defective in Δ12 desaturase produced anoil containing only ω 9 PUFAs. The mycelial mead acid content reached 141 mg/g dry mycelia (1.9 g/L). An oil rich inω3 PUFAs was produced by the same mutant when grown in a medium containing linseed oil.The content of total co 3 PUFAs (i. e., a ?linolenic acid + cis-8, cis-11, cis-14, cis-17-icosatetraenoic acid + cis-5, cis-8, cis-11, cis-14, cis-17-icosapentaenoic acid) reached nearly 50 % in total mycelial fatty acid.
The accumulation of polyunsaturated fatty acids (PUFA) in Euglena and utilization were, studied. Fatty acids in growth media are incorporated and accumulate in cells. The fatty acid composition of Euglena can thus be controlled by supplementation with fatty acids. The Dietary value of zooplankton for larval red sea bream was greatly improved by enrichment with DHA-enriched Euglena. In particular, zooplankton enriched with DHA-enriched Euglena showed higher activity of larval red sea bream than the present feed.
Nannochloropsis oculata (also called marine chlorella) is a marine unicellular algae used as a feedstuff in the Japanese aquaculture industry. Due to the high fat and icosapentaenoic acid (EPA) content, it serves as high nutritional feed in the food chain for fish hatchlings. EPA content of the organism could be modulated from 20 % to 40 % total extractable fat by varying the culture conditions. The maximum fat content of Nannochloropsis was about 30 % by weight, and the optimal cell density of 2.5×108 cells/mL achieved using a specially developed outdoor tank technology. Nannochloropsis lipid was predominantly polar (phospholipid and glycolipid), and the glycolipid fractions (mono-and digalactosyl diacylglycerols) contained over 70 % EPA in their fatty acid moieties. Due to the absence of docosahexaenoic acid (DHA), EPA from Nannochloropsis could be easily purified to over 95 %. Dietary supplementation of spontaneously hypertensive rats with intact Nannochloropsis cells resulted in a significant reduction of the saltinduced increase in blood pressure. However, these high fat/high EPA microalgae may be of the greatest use to the aquaculture industry as feed for zooplankton (brine shrimp and rotifers) cultures. Nannochloropsis-fed zooplankton was found to serve as a highly nutritious live feed which significantly increased the survival of the hatchlings of many cultured fish.
Icosapentaenoic acid (EPA) -producing bacteria were isolated from intestinal contents of marine animals. Shewanella sp. strain SCRC-2738, which is one of the many excellent EPA-producing bacteria, was examined for EPA productivity, usefulness for our health and industrial utilization and synthetic mechanism of the EPA. The major lipids of the strain were phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). The ratio of EPA were 14.6 % of total fatty acid in PE and 40.4 % of that in PG. The maximum EPA productivity was 376.4 mg/L culture broth. The strain incorporates exogenous docosahexaenoic acid (DHA) into phospholipids without a change of the endogenous EPA productivity. It is possible that the strain synthesize EPA via pathway different from those of higher plants and algae, although the enzyme participated the pathway is still unknown in detail.
Bioconversions of lipids and their related compounds catalyzed by microbial cells in organic solvents are reviewed historically. First, characteristics involved in such biochemical reaction systems are summarized by combining the idea of reactions catalyzed by enzymatically active resting or dead cells with the idea of biochemical reactions in organic solvents. Such reaction systems are then classified broadly into two ; those by wet cells and those by dry cells, and each is subdivided into two ; by freely suspended cells and immobilized cells. Various biochemical reactions reported so far in these four categories (suspended wet cells, immobilized wet cells, suspended dry cells and immobilized dry cells) are introduced to review. Prerequisites are made clear to realize these reactions industrially. Importance of moisture control is emphasized for the case of utilization of dry cells. Prospects are mentioned for this area by suggesting bothfinding social needs and screening microorganisms having greater activities.
The optimum conditions for quantitative conversions of phosphatidylcholine (PC) concentrated soy phospholipid into phosphatidic acid (PA) or phosphatidylglycerol (PG) were examined with crude phospholipase D prepared from fresh cabbages. The results showed that the phospholipase D used had a pH-dependency in hydrolysis or transphosphatidylation, that is, the complete hydrolysis from PC to PA and transphosphatidylation from PC to PG occurred under pH 5.6 and 4.8, respectively. Therefore, the competitive hydrolysis could be inhibited effectively in PG preparation from PC by adjusting the pH with an acetate buffer solution (pH 4.8). Under the optimum conditions determined, PC and PE were converted quantitatively into PA or PG by hydrolysis or transphosphatidylation with the phospholipase D, respectively, although phosphatidylinositol (PI) did not change at all.
The relationship between electric capacitance of foam and the real liquid volume fraction of the foam was investigated. The foam was formed by injecting air into sodium dodecyl sulfate solution, and sent into a tube of i.d. of 12.0 mm and o.d. of 17.0 mm. The tube was placed between two parallel plate electrodes. Capacitance across the twin electrodes was measured. Foam that the passed through the tube was captured in a bag and weighed for accurate determination of the liquid volume fraction. Apparent relative electric capacity Kx, determined by factors such as the tube, was measured. When liquid volume fractions σ increases from 0 to 1, Kx increases from 0 to 1. Kx showed better correspondence to the liquid volume fraction than the dielectric constant of foam εx, in which εx was calculated. This method is suitable for measuring liquid volume fraction of dry foam since Kx is 0.9 when a is 0.057. A linear relation between a and Kx was obtained when σ increased from 0.005 to 0.05. Foam drainage was measured by this method. The flow rate of air injection is clearly shown to be affected by the shape of the foam drainage curve.