High-cell-density poly (3-hydroxybutyrate) production from sucrose using Burkholderia sacchari culture in airlift bioreactor.

Burkholderia sacchari IPT 189 poly (3-hydroxybutyrate) (P3HB) production in airlift bioreactor were investigated in batch and fed-batch culture using sucrose as carbon source. In batch experiments it was observed that during the growth phase B. sacchari IPT 189 might display exponential growth even at very low carbohydrate concentration, as long as NH(4)(+) concentration was above 190 mg l(-1). The onset of accumulation phase took place when NH(4)(+) concentration dropped below this value and continued as long as carbohydrate was in excess, even with dissolved oxygen concentration at 0.0% of air saturation. In the fed-batch experiments, nitrogen limitation was used to induce P3HB biosynthesis in a two-phase process. In the first phase, an initial batch followed by a limited sucrose fed regime led to a growth with low-P3HB-content (less than 13%) and up to 60 g l(-1) of biomass concentration in c.a. 25 h. In the second phase, nitrogen concentration limitation induced P3HB accumulation up to 42%, raising the biomass concentration to c.a. 150 g l(-1). Calculated parameters for the experiments were P3HB productivity=1.7 gl(-1) h(-1) and P3HB yield factor from sucrose=0.22 g g(-1).

Comparative study of nanohydroxyapatite microspheres for medical applications.

This study concerns the preparation, physical, and in vitro characterization of two different types of hydroxyapatite (HA) microspheres, which are intended to be used as drug-delivery systems and bone-regeneration matrices. Hydroxyapatite nanoparticles (HA-1 and HA-2) were prepared using the chemical precipitation synthesis with H(3)PO(4), Ca(OH)(2), and a surfactant, SDS (sodium dodecyl sulfate), as starting reagents. The HA powders were dispersed in a sodium alginate solution, and spherical particles were obtained by droplet extrusion coupled with ionotropic gelation in the presence of Ca(2+). These were subsequently sintered to produce HA-1 and HA-2 microspheres with a uniform size and interconnected microporosity. Both powders and microspheres were characterized using FTIR and X-ray diffraction. Moreover, SEM and mercury intrusion porosimetry were used to analyze the microspheres, and TEM was used to analyze the powders. Results showed that pure HA and mixtures of HA/beta-TCP in the nanometer range and needlelike shape were obtained for HA-1 and HA-2 powders, respectively. Neutral Red, scanning electron microscopy and confocal microscopy were used to evaluate the behavior of osteoblastic-like MG-63 cells cultured on HA microspheres surfaces for 7 days. Results showed that good adhesion and proliferation of osteoblasts on the HA microspheres surface. Cells built bridges between adjacent microspheres, forming microspheres-cells clusters in both types of materials.