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The enhancement of epsilon-poly-l-lysine (epsilon-PL) production by Streptomyces albulus strain no. 410 (S410) by means of a pH control strategy was investigated. S140 cells produce epsilon-PL at a high concentration if the culture pH remains at about 4.0; however, if it shifts to higher than 4.0, the accumulated epsilon-PL is depolymerized. We therefore suggest a pH control strategy for cell growth and epsilon-PL production aimed at increasing the amount of epsilon-PL produced. The cultivation was divided into two control phases. In phase I, cell growth was accelerated by maintaining the pH at higher than 5.0; in phase II, epsilon-PL production was increased by maintaining the pH at about 4.0. To avoid an increase in the pH during phase II as a result of glucose depletion, the glucose concentration was kept at around 10 g/l by glucose feeding. This control strategy enhanced the production of epsilon-PL to 48.3 g/l from 5.7 g/l in the case of batch culture.

In vitro, -polylysine (EPL) strongly inhibited the hydrolysis of trioleoylglycerol emulsified with phosphatidylcholine (PC) and taurocholate by either pancreatic lipase or carboxylester lipase. The EPL concentration required for 50% inhibition of pancreatic lipase, 0.12 microM, was eight times lower than the concentration of orlistat required for the same effect. The 50% inhibition concentration by EPL was affected by emulsifier species: it was increased approximately 150 times, 70 times, and 230 times on gum arabic, phosphatidylserine, and phosphatidic acid emulsion, respectively, compared with PC emulsion. The 50% inhibition concentration by orlistat was little changed by emulsifier species. Gel-filtration experiments suggested that EPL did not bind strongly to pancreatic lipase, whereas orlistat did. To test the effect of EPL on obesity, mice were fed a high-fat diet containing 0.1, 0.2, or 0.4% EPL. EPL prevented the high-fat diet-induced increase in body weight and weight of the liver and visceral adipose tissues (epididymal and retroperitoneal). EPL also decreased plasma triacylglycerol and plasma cholesterol concentrations and liver triacylglycerol content after they had been increased by the high-fat diet. The fecal weights of mice were increased by the high-fat diet containing EPL compared with the high-fat diet alone. Fecal lipid was also increased by the diet containing EPL. These data clearly show that EPL has an antiobesity function in mice fed a high-fat diet that acts by inhibiting intestinal absorption of dietary fat.

No abstract

Basic polysaccharide strongly inhibited the hydrolysis of trioleoylglycerol (TO) emulsified with phosphatidylcholine and taurocholate by either pancreatic lipase or carboxylester lipase. DEAE-Sephadex dose-dependently inhibited the hydrolysis of TO by pancreatic lipase and carboxylester lipase; however, carboxymethyl-Sephadex and Sephadex G-50 did not inhibit the hydrolysis. Polydextrose (PD), a soluble polysaccharide, was a very weak inhibitor of pancreatic lipase. However, when a basic group, a DEAE group, was attached to PD, lipase inhibition by DEAE-PD was increased, and this was dependent on the substitution ratio of DEAE groups. The number of positive charges per PD molecule is important in lipase inhibition. Similar substitution effects were observed with other basic groups, such as piperidinoethyl and 3-triethylamino-2-hydroxypropyl. The natural basic polysaccharide, chitosan, also inhibited pancreatic lipase activity. Gel-filtration experiments suggested that DEAE-PD did not bind strongly to pancreatic lipase. The effect of DEAE-PD on TO hydrolysis by pancreatic lipase was studied using various emulsifiers: DEAE-PD (50 mg/ml) did not inhibit the hydrolysis of TO emulsified with arabic gum, phosphatidylserine, or phosphatidic acid. In vivo, oral administration of DEAE-PD to rats reduced the peak plasma triacylglycerol concentration and increased fecal lipid excretion. These results suggest that basic polysaccharide is able to suppress dietary fat absorption from the small intestine by inhibiting pancreatic lipase activity.-Tsujita, T., H. Takaichi, T. Takaku, T. Sawai, N. Yoshida, and J. Hiraki. Inhibition of lipase activities by basic polysaccharide. J. Lipid Res. 2007. 48: 358-365.