Amelogenin-deficient mice display an amelogenesis imperfecta phenotype.

Dental enamel is the hardest tissue in the body and cannot be replaced or repaired, because the enamel secreting cells are lost at tooth eruption. X-linked amelogenesis imperfecta (MIM 301200), a phenotypically diverse hereditary disorder affecting enamel development, is caused by deletions or point mutations in the human X-chromosomal amelogenin gene. Although the precise functions of the amelogenin proteins in enamel formation are not well defined, these proteins constitute 90% of the enamel organic matrix. We have disrupted the amelogenin locus to generate amelogenin null mice, which display distinctly abnormal teeth as early as 2 weeks of age with chalky-white discoloration. Microradiography revealed broken tips of incisors and molars and scanning electron microscopy analysis indicated disorganized hypoplastic enamel. The amelogenin null phenotype reveals that the amelogenins are apparently not required for initiation of mineral crystal formation but rather for the organization of crystal pattern and regulation of enamel thickness. These null mice will be useful for understanding the functions of amelogenin proteins during enamel formation and for developing therapeutic approaches for treating this developmental defect that affects the enamel.     

Functional Imaging of Chemically Active Surfaces with Optical Reporter Microbeads

We have developed a novel approach to allow for continuous imaging of concentration fields that evolve at surfaces due to release, uptake, and mass transport of molecules, without significant interference of the concentration fields by the chemical imaging itself. The technique utilizes optical “reporter” microbeads immobilized in a thin layer of transparent and inert hydrogel on top of the surface. The hydrogel has minimal density and therefore diffusion in and across it is like in water. Imaging the immobilized microbeads over time provides quantitative concentration measurements at each location where an optical reporter resides. Using image analysis in post-processing these spatially discrete measurements can be transformed into contiguous maps of the dynamic concentration field across the entire surface. If the microbeads are small enough relative to the dimensions of the region of interest and sparsely applied then chemical imaging will not noticeably affect the evolution of concentration fields. In this work colorimetric optode microbeads a few micrometers in diameter were used to image surface concentration distributions on the millimeter scale.     

Ethanol production from alfalfa fiber fractions by saccharification and fermentation

This work describes ethanol production from alfalfa fiber using separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) with and without liquid hot water (LHW) pretreatment. Candida shehatae FPL-702 produced 5 and 6.4 g/l ethanol with a yield of 0.25 and 0.16 g ethanol/g sugar respectively by SHF and SSF from alfalfa fiber without pretreatment. With LHW pretreatment using SSF, C. shehatae FPL-702 produced 18.0 g/l ethanol, a yield of 0.45 g ethanol/g sugar from cellulosic solids or ‘raffinate’. Using SHF, it produced 9.6 g/l ethanol, a yield of 0.47 g ethanol/g sugar from raffinate. However, the soluble extract fraction containing hemicelluloses was poorly fermented in both SHF and SSF due to the presence of inhibitors. Addition of dilute acid during LHW pretreatment of alfalfa fiber resulted in fractions that were poorly saccharified and fermented. These results show that unpretreated alfalfa fiber produced a lower ethanol yield. Although LHW pretreatment can increase ethanol production from raffinate fiber fractions, it does not increase production from the hemicellulosic and pectin fractions.     

Ethanol production from d-xylose in batch fermentations with Candida shehatae: process variables

Summary These studies examined several process variables important in scaling up the fermentation of xylose by Candida shehatae. Inoculum age and cell density were particularly influential. Young (24-h) inocula fermented xylose to ethanol two to three times as fast as older (48- or 72-h) inocula. With all three inocula ages, the initial fermentation rates were essentially linear with cell density, up to 4 g dry wt cells L^-1. Above that cell density, the ethanol production rate appeared to be oxygen limited, particularly with 24-h old cells. Aeration also played a role in xylose utilization. The fermentation proceeded under both aerobic and anaerobic conditions, but xylose was not completely utilized anaerobically. With aeration, 25% more ethanol was formed in about one third the time than without aeration. Ethanol yields were similar under the two conditions. Cell growth on xylose was observed in the absence of oxygen. Cells went through essentially one doubling in 24 h. Based on the sugar consumed, a Y _ATP of 9.9 was obtained. Slow continuous feeding of glucose significantly increased the xylose utilization rate.Maintained in cooperation with the University of Wisconsin, Madison, Wisconsin, USA