Lipid entrapment property of polysaccharide gel (PG) extracted from fruit-hulls of durian (Durio zibethinus Murr. Cv. Mon-Thong)

Lipid entrapment property of polysaccharide gel (PG) extracted from fruit-hulls of durian (Durio zibethinus Murr. Cv. Mon-Thong) was investigated in vitro by semi- permeable membrane dialysis technique using both cellulose membrane and gut sacs of disected jejunum of rat. Lipids (cholesterol, oleic acid and stearic acid) were mixed with 0-2%W/V PG in the presence of bile salt as a surface active agent in dialysis membrane. Lipids inside and outside dialysis membrane were analyzed by HPLC method after 4-16 hours of dialysis in Ringer lactate buffer pH7. Increasing PG concentration resulted in increasing lipids trapped inside membrane and decreasing lipids released outside membrane. Two percent PG trapped about 80-90%cholesterol. The result of PG trapping cholesterol in egg york showed that egg york cholesterol released outside membrane was decreased with increasing PG concentration. A significant relationship was found between the decreasing of absorbed cholesterol into everted rat jejunum with respect to increasing concen- tration of PG. These results suggested that durian polysaccharide gel is able to entrap lipids and it seems to have potential use as medicinal dietary food for lipid controlling patient. Furthermore, in vitro study using cellulose semi- permeable membrane dialysis method may be applied for preliminary evaluation of polysaccharide effecting lipids absorption

Citrate Synthase Mutants of Agrobacterium Are Attenuated in Virulence and Display Reduced vir Gene Induction

A citrate synthase (CS) deletion mutant of Agrobacterium tumefaciens C58 is highly attenuated in virulence. The identity of the mutant was initially determined from its amino acid sequence, which is 68% identical to Escherichia coli and 77% identical to Brucella melitensis. The mutant lost all CS enzymatic activity, and a cloned CS gene complemented a CS mutation in Sinorhizobium. The CS mutation resulted in a 10-fold reduction in vir gene expression, which likely accounts for the attenuated virulence. When a plasmid containing a constitutive virG [virG(Con)] locus was introduced into this mutant, the level of vir gene induction was restored to nearly wild-type level. Further, the virG(Con)-complemented CS mutant strain induced tumors that were similar in size and number to those induced by the parental strain. The CS mutation resulted in only a minor reduction in growth rate in a glucose-salts medium. Both the CS mutant and the virG(Con)-complemented CS strain displayed similar growth deficiencies in a glucose-salts medium, indicating that the reduced growth rate of the CS mutant could not be responsible for the attenuated virulence. A search of the genome of A. tumefaciens C58 revealed four proteins, encoded on different replicons, with conserved CS motifs. However, only the locus that when mutated resulted in an attenuated phenotype has CS activity. Mutations in the other three loci did not result in attenuated virulence and any loss of CS activity, and none were able to complement the CS mutation in Sinorhizobium. The function of these loci remains unknown