Depolymerized konjac glucomannan: preparation and application in health care / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Konjac glucomannan (KGM) is a water-soluble polysaccharide obtained from the roots and tubers of konjac plants. Recently, a degraded product of KGM, depolymerized KGM (DKGM), has attracted attention because of its low viscosity, improved hydrophily, and favorable physiological functions. In this review, we describe the preparation of DKGM and its prebiotic effects. Other health benefits of DKGM, covering antioxidant and immune activity, are also discussed, as well as its safety. DKGM could be a candidate for use as a tool for the treatment of various diseases, including intestinal flora imbalance, and oxidative- and immune-related disorders.

Identification and mode of action of a xylanase A purified from the culture filtrate of Bacillus pumilus WL-11 / 生物工程学报

Microbial xylanases have received a great deal of attention in the last two decades for their potential applications in food, paper making and animal feed industries. Bacillus pumilus WL-11 was identified as a producer of alkane xylanase free of cellulase after screening soil samples of paper-making factories. The xylanase A (XylA) was purified to homogeneity from the culture filtrate of Bacillus pumilus WL-11 by (NH4) 2SO4 precipitation, CM-Sephadex and Sephadex G-75 chromatographies. The molecular mass of XylA is estimated to be 26.0 kD by SDS-PAGE and its isoelectric point is 9.5. The apparent Km is 16.6 mg/mL and V(max) is 1263 micromol/(min x mg) towards oat spelt xylan. XylA is optimally active between pH 7.2 and 8.0, and stable at pH 6.0 to 10.4. The enzyme is optimally active at 45 degrees C - 55 degrees C and stable at temperature below 45 degrees C, with its half time of activity of 35 min and 15 min at 55 degrees C and 60 degrees C respectively. HPLC analysis revealed that hydrolysis patterns of xylans from oat spelt, birch wood and beech wood by purified XylA were different. The XylA is determined to be an endo-beta-1,4-xylanase, as it generated mainly xylotriose and no xylose was detected among the three hydrolysates. XylA has strong hydrolytic activity towards the pentose in the hydrolysates of beech wood and birch wood xylans, but was not active to the pentose in the hydrolysate of oat spelt xylan. The crude WL-11 enzyme can efficiently hydrolyze oat spelt xylan to a series of xylo-oligosaccharides, suggesting its potential application in nutraceutical industry.

Purification and characterization of a monofunctional catalase from an alkaliphilic Bacillus sp. F26 / 生物工程学报

An alkaline catalase has been purified and characterized from a slightly halophilic and alkaliphilic bacterium Bacillus sp. F26. The purification was performed with a four step procedure consisting of ammonium sulfate precipitation, ion exchange, gel filtration and hydrophobic interaction chromatography, and finally achieved a 58.5-fold-purifying over the crude extract. The purified catalase was composed of two identical subunits with a native molecular mass of 140 kD. The native enzyme showed the typical Soret band appearing at 408 nm. The pyridine hemochrome spectrum indicated the presence of protoheme IX as the prosthetic group. The apparent Km value for enzyme activity on H2O2 was calculated to be 32.5 mmol/L. The activity of this catalase was not reduced by dithionite but was strongly inhibited by cyanide, azide, and 3-amino-1,2,4-triazole (the specific inhibitor of monofunctional catalase). No peroxidase activity of this enzyme was detected when using o-dianisidine, diaminobenzidine (DAB) and p-phenylenediamine as electron donor. Moreover, the N-terminal sequence of this catalase exhibited substantial similarity to the monofunctional catalase subgroup rather than catalase-peroxidase or Mn-catalase one. Therefore, we characterize the purified catalase as a monofunctional catalase. Besides, this monofunctional catalase was thermosensitive and its activity exhibited pH-independent over pH 5-9 but showed a sharp maximum at pH 11. An activity half-life of approximately 49 h was measured when the enzyme was incubated at 20 degrees C and pH 11. To our knowledge, pH 11 is the most alkaline condition for optimum catalysis and enzyme stability among the catalases reported up to now. Furthermore, this monofunctional catalase also showed excellent halo-alkali-stability with a half-life of approximately 90 h at 0.5 mol/L NaCl and pH 10.5. On the other hand, so far as we know, the characterized catalase is the first dimeric monofunctional catalase from alkaliphiles and is also the first monofunctional catalase derived from a natural soda lake, which could partially reflect the oxidative stress response in the corresponding environment.

The stability of insulin-loaded polybutylcyanoacrylate nanoparticles in an oily medium and the hypoglycemic effect in diabetic rats / 药学学报

<p><b>AIM</b>To study the stability of insulin-loaded polybutylcyanoacrylate nanoparticles (IPN) in an oily medium (soybean oil containing 0.5% (v/v) Tween-20 and 5% (v/v) Vitamin E) along with the hypoglycemic effect following their oral administration to streptozotocin (STZ) induced diabetic rats.</p><p><b>METHODS</b>The stability of IPN in the process was appraised by measurement of the amount of undegraded insulin associated to nanoparticles, the average size and the span of IPN, as well as the release of insulin from IPN. IPN in an aqueous medium (containing 0.5% (v/v) Tween-20) at pH 2.0 was also investigated as control.</p><p><b>RESULTS</b>The study showed that IPN in the oily medium was more stable than that in the aqueous medium over one year of storage in the dark at (25 +/- 2) degrees C and the in vitro stability of IPN in the oily medium against degradation by proteolytic enzymes was much better than that in the aqueous medium. The apparent bioavailability of an oral administration of IPN (50 u x kg(-1)) in the oily medium versus an (sc) injection of insulin (2 u x kg(-1)) was 22.4%, much higher than that of IPN in the aqueous medium (15.5%), based on decreased areas above curve (AAC) determination for the blood glucose depression from time zero to 144 h of a single oral administration of IPN to STZ-diabetic rats.</p><p><b>CONCLUSION</b>IPN in soybean oil containing Tween-20 (0.5% v/v) and Vitamin E (5% v/v) could be considered as an effective and stable delivery system for oral insulin.</p>

Advances in the Research on Microbial Phytases / 微生物学通报

Phytases are studied widely in plants and microorganisms. Interest in these enzymes has been stimulated by the fact that phytase has the advantage in forage, food process and medicine. This paper reviews recent trends on the production, purification, properties and gene of microbial phytases.

Screening of Lipase-producing Strain for Catalytic Synthesis of Ester in Organic Media / 微生物学通报

An organic solvent tolerant isolate A213 originating from soil samples were successfully isolated via direct plating method using 10g/L of toluene as the sole carbon source and transparent cycle plate assay method.It was identified as Yarrowia based on its characteris- tics.The results in shake flask cultivation showed that the suitable tipase producing media were(g/L):yeast extract 40,vegetable oil 10, MgSO_4?7H_2O1,KH_2PO_4 5.Under optimal culture conditions (27℃and pH 6.5 ),the maximal lipase activity could reach 67.8 IU/ mL The optimal pH and temperature for the hydrolysis of p-nitrophenyl acetate by crude lipase were pH6.5 and 40℃The enzyme was sta- ble under 70℃and pH 5.5～8.5.Then isolate A213 was found to produce the lipase which can synthesize L-ascorbyl palmitate in tert-amyl alcohol validated by the thin-layer chromatography.