The main source of calcium carbonate (CaCO3) in the ocean comes from the shells of calcifying planktonic organisms, but substantial amounts of CaCO3 are also produced in fish intestines. The precipitation of CaCO3 assists fish in intestinal water absorption and aids in whole body Ca2+ homeostasis. Here we report that the product formed in the intestinal lumen of the gilt-head seabream, Sparus aurata, is an amorphous calcium carbonate (ACC) phase. With FTIR spectroscopy and SEM imaging, our study shows that the fish-derived carbonates from S. aurata are maintained as a stable amorphous phase throughout the intestinal tract. Moreover, intestinal deposits contained up to 54 mol% Mg2+, the highest concentration yet reported in biogenic ACC. Mg is most likely responsible for stabilizing this inherently unstable mineral. The fish carbonates also displayed initial rapid dissolution when exposed to seawater, exhibiting a significant increase in carbonate concentration.

No abstract

Ulvan is a complex sulfated polysaccharide biosynthesized by green seaweed and contains predominantly rhamnose, xylose, and uronic acid sugars. Ulvan-degrading enzymes have only recently been identified and added to the CAZy ( www.cazy.org ) database as family PL24, but neither their structure nor catalytic mechanism(s) are yet known. Several homologous, new ulvan lyases, have been discovered in Pseudoalteromonas sp. strain PLSV, Alteromonas LOR, and Nonlabens ulvanivorans, defining a new family PL25, with the lyase encoded by the gene PLSV_3936 being one of them. This enzyme cleaves the glycosidic bond between 3-sulfated rhamnose (R3S) and glucuronic acid (GlcA) or iduronic acid (IdoA) via a β-elimination mechanism. We report the crystal structure of PLSV_3936 and its complex with a tetrasaccharide substrate. PLSV_3936 folds into a seven-bladed β-propeller, with each blade consisting of four antiparallel β-strands. Sequence conservation analysis identified a highly conserved region lining at one end of a deep crevice on the protein surface. The putative active site was identified by mutagenesis and activity measurements. Crystal structure of the enzyme with a bound tetrasaccharide substrate confirmed the identity of base and acid residues and allowed determination of the catalytic mechanism and also the identification of residues neutralizing the uronic acid carboxylic group. The PLSV_3936 structure provides an example of a convergent evolution among polysaccharide lyases toward a common active site architecture embedded in distinct folds.

Baker's yeast, Saccharomyces cerevisiae, is reported as possessing the ability to convert glycerol to 1,3-propanediol. Various fermentation conditions were tested at different temperatures. Under anaerobic fermentation at 25 °C, 93.6 wt% glycerol was consumed, yielding 42.3 wt% 1,3-propanediol.

This review discusses the current methodologies and recent developments for bioethanol production from biomass. We demonstrate the future aspects of bioethanol production in solar reactors, and strategies to improve process yields as well as the prospects of using a solar reactor to produce other valuable chemicals.

No abstract

Among the many newer disclosures that have accompanied the petroleumindustry's progressively deeper exploratory drilling is the increased frequencywith which the operators are encountering reservoirs of which the products atthe time of discovery exist wholly or predominantly in the gas phase. Thepopular term "distillate pool" is most often used within the industrywhen referring to this type of reservoir, and in this paper the term is used inthat sense. These pools have been observed in many different surroundings. Insome places the entire reservoir is filled with the wet gas containing itswater-white condensible products in the gas phase but apparently with no darkoil or other hydrocarbon liquids in the reservoir. The 8200-ft. horizon in theBig Lake field in West Texas is a good example of this type. At other placesthe wet, or distillate-bearing, gas may form a large gas cap directly overlyingand in contact with an extensive reserve of dark oil. Oklahoma City, KettlemanHills, the 8500-ft. horizon in the Big Lake field, and many others are examplesof this type. There are also many places in which the wet distillate-bearinggas fills nearly the entire reservoir space, while the dark oil occupies only anarrow, band-like zone, which marks the boundary of the reservoir along itslowest productive contour. The heavier components of these deep pool gases are generally water white incolor, a large portion of which are condensible in a conventional oil and gasseparator, when operated under pressures of the order of 400 to 800 lb. per sq.in. Although the water-white products recovered in the separator sometimes haveend points of 6500 F. and higher on standard Engler distillation, they occuronly in the gas phase in the reservoir. It is entirely possible that even somesmall amounts of dark colored reservoir components may occur in the gas phasewhen the temperature is 3000 F. and pressures exceed 6000 lb. per sq. in. Closeapproaches to these conditions have been encountered in the deepest producingwells. The condensible content of the deep reservoir gases of the many poolsthat have been tested or produced to date shows a wide variation in bothcondensible content, per 1000 cu. ft. of gas, and physical character. T.P. 1023

THE repressuring of oil-producing formations during the flush stage of production, although requiring primarily the same procedure as operations on formations where the gas pressure has been depleted, offers several advantages of major importance, the value of which has not heretofore been demonstrated. It is the purpose of this paper to present an account of some recent operations of this character and the economic effects on the properties where they were applied.The principal objective in all repressuring operations is to secure an effective diffusion of the input energy to all parts of the producing sand. If this can be accomplished, success is assured during the remainder of the life of the property; if not, it will be temporary only and will be followed by difficulties, and the maximum possible recovery will not be obtained.During the past year in Texas, the Cook pool in Shackelford County, and the Turbeville pool in Archer County, while still in their flush stage of production, have been subjected to repressuring operations to observe their reaction to this process during the early stage of their productive periods. The repressuring operations carried on in each of these pools will be discussed separately in this paper in order to show peculiarities which were present in one pool but were not observed in the other.