C3A cell behaviors on micropatterned chitosan collagen gelatin membranes.

The influence of the properties and surface micropatterning of chitosan-collagen-gelatin (CCG) blended membranes on C3A cell's activities has been investigated. It is aimed to guide the cell growth and improve the growth rate in vitro for the application in tissue engineering. Masters with micropatterns are prepared on stainless steel plates by photolithography. The CCG membranes with surface micropatterns are then fabricated by soft lithography and dry-wet phase inversion techniques. The morphology and metabolic activity of cultured C3A cells on the membranes are recorded. When the C3A cells are seeded on the membranes with micropattern spacing of 200 microm width and 80 microm depth, they adhere and aggregate in the groove of the membranes in a few minutes. The aggregated cells migrate up to the surface of the ridge later. This phenomenon, however, is not found on membranes with a micropattern spacing of 500 microm width. In addition, it is demonstrated that the cells on the CCG membranes with micropatterns have higher metabolism and growth rates than those on the flat CCG membranes and on T-flask discs. Micropatterning on the membrane surface can affect the distribution of cells and the communication among cells, and results in a difference in cell adhesion, morphology, mobility, and growth activity.

Production of poly-beta-hydroxybutyrate (PHB) by Vibrio spp. isolated from marine environment.

Bacteria isolated from marine sediments were screened for their ability to accumulate polyhydroxyalkanoates. Among the isolates, four Vibrio spp. (strain M11, M14, M20 and M31) were studied in detail. All synthesized intracellular lipid inclusions during growth on diverse carbon sources including acetate, glycerol, succinate, glucose and sucrose. The inclusions were identified to be poly-beta-hydroxybutyrate (PHB) using gas chromatography and nuclear magnetic resonance analysis. No other type of polyhydroxyalkanoates (PHAs) was found to be accumulated by these marine isolates, suggesting that the diversity of PHAs produced in marine environments may be not as versatile as found in other environments. Strain M11 accumulated PHB in concentrations as high as 41% of cell dry weight when grown in medium containing 4% of sodium chloride. One of the Vibrio spp. was identified to be closely related to Vibrio natriegens (98% identity) by partial 16S rDNA sequence homology. V. natriegens has the shortest generation time (9.8 min) of any bacterium and this characteristic may be an exploitable trait for the industrial production of PHB.

Identification of induced acidification in iron-enriched cultures of Bacillus subtilis during biosurfactant fermentation.

Bacillus subtilis is able to synthesize a lipopeptide biosurfactant (known as surfactin), which is one of the most effective biosurfactants available. In our previous study, B. subtilis ATCC 21332 was used to produce surfactant and it was found that the addition of iron at an appropriate amount significantly improved the biosurfactant production. However, it also showed that excess addition of iron led to a sharp decrease in pH of the culture and surfactin in the broth disappeared rapidly once the pH fell below 5.0. This study reveals that the disappearance of surfactin at the acidic pH was due to the precipitation of surfactin triggered by the accumulation of extracellular acidic metabolites. The acidic material was isolated and purified from the broth and was characterized by GC-MS and IR spectroscopy. The results of GC-MS and IR analysis show that the molecular weight and molecular structure of the acidic metabolite resembled those of phthalic anhydride.