Exploration on the bioreduction mechanism of Cr(â ¥) by a gram-positive bacterium: Pseudochrobactrum saccharolyticum W1.

Bioremediation of chromium (Cr(Ⅵ)) contaminations has been widely reported, but the research on its removal mechanism is still scarce. Studies on Cr(Ⅵ) removal by strains affiliated to genus Pseudochobactrum revealed the Cr(Ⅵ) efficiency removal through the reduction of Cr(Ⅵ) to Cr(Ⅲ). However, the location of Cr(Ⅵ) reduction reaction and exact mechanism are still unspecified. In this work, a Gram-positive bacterial strain, Pseudochrobactrum saccharolyticum W1 (P. saccharolyticum W1) was isolated and tested to remove approximately 53.7% of Cr(Ⅵ) (initial concentration was 200 mg L-1) from the MSM medium. Analysis of SEM-EDS and TEM-EDS indicated that chromium-containing particles precipitated both on the cell surface and in the cytoplasm. Batch experiments indicated that the heat-treated bacterial cells almost had no ability to remove Cr(Ⅵ) from solution, while the resting cells could remove 62.0% of Cr(Ⅵ) at the initial concentration of 10 mg L-1. Additionally, at this concentration, 64.8% and 70.8% of Cr(Ⅵ) was reduced by cell envelope components and intracellular soluble substances after 6 h, respectively. These results suggested that the removal of Cr(Ⅵ) by P. saccharolyticum W1 was through direct reduction, which occurred on both cell envelop and cytoplasm. The results also showed that cytoplasm was the main site for Cr(Ⅵ) reduction compared to the cell envelop. Further analysis of FTIR and XPS verified that C-H, C-C, CO, C-OH and C-O-C groups of cells involved in correlation with chromium during Cr(Ⅵ) reduction. The study offered an insight into the Cr(VI) reduction mechanism of P. saccharolyticum W1.

P48-A109†Obstacles and perspectives in tissue engineered endothelial keratoplasty.

Endothelial bioengineering is the simplest form of corneal bioengineering insofar as it consists of producing a large quantity of corneal endothelial cells and packaging them in a form that can be transplanted to the patient. It seems to be the most realistic solution to replace endothelial grafts made from donor corneas and thus allow, by domino effect, to reserve them for other indications of keratoplasty. Kyoto ophthalmologists (S Kinoshita, N Koizumi and N Okumura) were the pioneers of injection therapy by demonstrating its feasibility and safety, with an efficacy at 5 years comparable to that of conventional endothelial grafts. These pioneers, split into two distinct entities, are currently industrializing this therapy by injecting cells in suspension, in the USA (Aurion biotech) and in Asia (Actualeyes). In addition to injections, tissue engineered endothelial keratoplasty (TEEK) is a complementary research approach. They consist in reproducing in vitro grafts of the DMEK or DSAEK type by seeding the cultured cells on a 'corneo-compatible' support. Several have passed the preclinical stages and one is in clinical trial in Asia. Suspension cells and TEEK each have advantages and limitations that make them complementary in the management of corneal endothelial diseases.We will analyze why there is not yet an alternative process for mass production of corneal endothelial cells or clinical grade TEEK, systematically detailing the various bottlenecks identified, from the source of cells and media, to regulatory and economic aspects.