Shiru Jia

Improvement of epsilon-Poly-L-Lysine Production by Streptomyces albulus TUST2 Employing a Feeding Strategy

Streptomyces albulus TUST2, separated from a soil sample of Hainan Island, was cultivated in a stirred, submerged aerated 5-1 bioreactor. Carbon source and nitrogen source effects were clarified in fed-batch fermentation, particularly glucose and ammonium sulfate feedings for enhancing the epsiv-poly-L-lysine (epsiv-PL) production were elucidated. The culture was divided into two control phases. In phase I , the pH was maintained at its initial 6.8 for 36 h for acquiring high biomass; In phase II, the pH was maintained at 4.0 aiming at increasing the epsiv-PL accumulation. Moreover, pulsed feeding of glucose (800 g/l) was carried out accompanied by ammonium sulfate (80 g/l) discontinuously when their concentration reached a lower level (nearly 10 g/l) in the medium, so that the final concentration of glucose can be kept at 13 g/l. By using this feeding policy, the elevation of antibacterial activity of epsiv-PL by S. albulus TUST2 is 16.67%, and its accumulation in 4-days cultivation is 20.20 g/l. We have illuminated that substrate feeding strategy is a doable method for improving epsiv-PL production by S. albulus TUST2.

PREPARATION AND APPLICATION OF BACTERIAL CELLULOSE SPHERE: A NOVEL BIOMATERIAL

ABSTRACT This paper explores preparation of spherical bacterial cellulose (BC), a novel biomaterial, and its adsorption capacity is charaterized. The effect of shaking speed and culture duration on fermentation production of BC spheres is analyzed; BC spheres are produced after 72 h fermention at 30°C with a shaking speed of 160 rpm. The spheres have a diameter range of 3–5 mm. The scanning electron micrograph photograph shows that BC spheres have a loose and porous structure. Repetition using tests on adsorption of Bovine serum albumin (BSA) and Pb2+ had been carried out. The results indicated that BC spheres can be recovered from BSA-BC complex and Pb-BC complex by eluting with NaOH and sodium citrate solution, respectively. So BC spheres have a vast potential for application in the fields of biomaterial bioseparation and sewage treatment.

Preparation and Characterization of Bacterial Cellulose Tube

Fermentation technique A (using oxygen-permeable tube as scaffold in fermentation vessel) and fermentation technique B (using oxygen-permeable tube as scaffold, also as fermentation vessel) were applied in preparation of bacterial cellulose (BC) tubes. Several types of oxygen-permeable tubes were tested in investigating their effects on biosynthesis of BC tubes by Gluconacetobacter xylinus. The results showed that tubular bacterial cellulose with uniform thickness when silicone tube was served as a scaffold. The BC production were significantly higher in technique B process than technique A. Tensile strengths of BC tubes were also measured, 0.35 MPa from technique A process, 50.25 MPa from technique B process. Scanning electron microscopy (SEM) revealed the BC structure of technique B tubes was more homogeneous and denser than that of technique A tubes. The BC tubes manufactured with silicone as oxygen-permeable scaffold according to fermentation technique B resulted in desired mechanical properties and were expected to be used as a scaffold for tissue engineered blood vessels and cellulose sausage casings.

Performance Improvement for Biomedical Material - Bacterial Cellulose

Bacterial cellulose has been deemed as a promising biomedical and tissue engineering material, due to the excellent biocompatibility, bio-degradability, water holding capacity and mechanical properties it possesses. This paper aims to improve its properties to meet the requirements of biomedical materials. The reasonable way is to impregnate BC pellicle with epsiv-PL solution and then immerse it into glycerol solution. Water absorbance, softness, flexibility, tensile strength and anti-bacterial activity have been improved successfully by aforesaid treatment.

The Study of Optimal Conditions of Electroporation in Gluconacetobacter Xylinum

The effect of electroporation conditions of Gluconacetobacter xylinum CGMCC 2955 was systematically investigated in this paper. The enzymolysis condition for removing bacterial cellulose of Gluconacetobacter xylinum was optimized by Response Surface Method, the result showed as follows: cellulase concentration 1046.4 IU/mL, enzymolysis duration 93.8 min at 30.6° C. Optimum conditions including growth stage of the strain, electroshock voltage, concentration and preservation of competent cell were defined for the electroporation of CGMCC 2955 with plasmid pDN19LacΩ. The result was showed that the highest transformation efficiency was up to 8.76×105 CFU/μg DNA under the optimium conditions in which the competent cells were collected at 2d and concentration to about 1×108 CFU/mL, the mixture of the competent cells and plasmid pDN19LacΩ was eletroporated at 2.4kV. The transformation efficiency is significantly reduced on account of -70° C preservation of competent cell.