Kinji Endo

Production of a Novel Extracellular Polysaccharide by a Bacillus Strain Isolated from Soil

A bacterium that was isolated from soil and identified as Bacillus circulans was found to produce a highly viscous extracellular polysaccharide when it was grown aerobically in a medium containing glucose as a sole source of carbon. The product was characterized by TLC and GC analyses as a novel heteropolysaccharide consisted of rhamnose, mannose, galactose, and mannuronic acid as sugar components. A maximal yield of polysaccharide reached about 2 g/liter by jar-fermentor culture at 30°C for 48 hr with a medium containing 1% glucose, 0.05% asparagine, 0.005% yeast extract, and small amounts of inorganic salts. Some culture conditions for the production of polysaccharide were investigated with flask culture; an optimal production was attained with a medium containing 0.1-1 % glucose and 0.01-0.05% asparagine, pH 7-8, at 30°C under aerobic conditions.

Properties of a Highly Viscous Polysaccharide Produced by a Bacillus Strain Isolated from Soil.

Chemical and Theological properties of a highly viscous and acidic polysaccharide produced by a soil bacterium identified as Bacillus circulans are described. The molecular weight of the native polysaccharide was about 116 × 10(4) by gel filtration with HPLC. The molar ratio of D-galactose, n-mannose, and L-rhamnose contained in the polysaccharide as neutral sugar components was 1.3:1:2. The viscosity of 1% solution of the polysaccharide was about 5000 cp, which was higher than that of guar gum, a seed polysaccharide, used as a reference standard. The viscosity was affected by the pH of the polysaccharide solution, a maximum viscosity being observed at pH 5.5 for native and decationized polysaccharide solution. The viscosity of 0.3% solution was decreased to about 70% by heating at 100°C and 22% at 120°C for 30 min as compared to the viscosity before heating. The addition of sugars, especially sucrose and glucose, at 10-30% concentration brought about a 130-180% increase of the viscosity. The addition of CaCl2 at a low concentration markedly increased the viscosity, and a maximum viscosity was attained at 2% concentration of the salt.

Induction of freeze-sensitive mutants from a freeze-tolerant yeast, Torulaspora delbrueckii

Freeze-sensitive strains of yeast were induced from a freeze-tolerant yeast Torulaspora delbrueckii by incubation with ethyl-methane sulfonate as a mutagen. A maximum ratio of mutation was attained by the incubation at 30°C for 75min. One-hundred and fifty strains of freeze-sensitive yeast were selected by plating-culture for the first screening. The freeze-tolerance ratio of each strain was examined based on the fermentative activity before and after freezing in liquid medium and dough. Strain 60B3 showed the highest freeze-sensitivity in a pre-fermented frozen dough (pre-fermented at 30°C for 2h, and frozen at -20°C for 7 days) among eight strains finally selected.

Temperature Dependency of 5′-Nucleotidase and Acid Phosphatase in Muscle Microsomes of Fish

Relationships between kinetics of IMP dephosphorylation by muscle microsomal enzymes and lipid composition of muscle microsomes were compared among fish of different habitat temperature, yellowtail, grunt, Spanish mackerel, rainbow trout and Pacific cod. The Km values of microsomal 5′-nucleotidase of fish except cod markedly increased at a temperature range below the break point on the Arrhenius plots of the enzyme activity. The break point temperatures in Arrhenius plots for microsomal 5′-nucleotidase were correlated with the content of saturated and polyunsaturated fatty acids in phospholipids of muscle microsomes in the fish examined. The results suggest that the occurrence of a break point in the Arrhenius plot of microsomal 5′-nucleotidase may be caused by the lipid phase transition of membranes that bind 5′-nucleotidase. Break point temperature may depend on microsomal lipid composition which is closely related to the habitat temperature of the fish.