Estimation of lipase activity by the diffusion plate method

A diffusion plate method for the assay of the activity of lipases in large series of samples was worked out. When using this method the maximum deviation was found to be ±3.8%.     

Deacylation of acetylated amino acids by the esterase fromMycobacterium phlei

In addition to typical acetyl esters, acetic ester aoetyl-hydrolase fromMycobacterium phlei can degrade aliphatic acetylated amino acids under suitable conditions.     

Functional organization of the human auditory cortex

We investigated the functional organization of the human auditory cortex using a novel electrophysiological recording technique combined with an advanced brain magnetic resonance imaging (MRI) technique. Tonotopic mapping data were obtained during single unit recording along the Heschl’s gyrus. Most of the units studied (73%) demonstrated sharply tuned excitatory responses. A tonotopic pattern was observed with the best frequencies systematically increasing as more medial-caudal recording sites were sampled. Additionally, a new auditory field along the posterior aspect of the superior temporal gyrus has been identified using a high spatial resolution direct recording technique. Results obtained during electrical stimulation demonstrate functional connectivity between the primary auditory cortex and the auditory field in the posterior superior temporal gyrus.     

Interaction of aflatoxin B1 with electron-donating organic molecules,including aromatic amino acids

The interaction of the carcinogenic mycotoxin, aflatoxin B₁, with some electrondonating organic compounds including aromatic hydrocarbons, dimethylaniline, and aromatic amino acids, was studied. Spectrophotometric analysis of aflatoxin B₁ revealed that hypochromicity in the absorption around 360 nm and hyperchromicity around 385 nm were induced by dimethylaniline, hexamethylbenzene, tryptophan, and imidazole. A similar shifting of aflatoxin B₁ absorption was observed in benzene, toluene, and xylene in the presence of ZnCl₂. The interaction of aflatoxin B₁ with polystyrene was observed in a biphasic system. The association constants of aflatoxin B₁: DMA⁴ (1:1) and of aflatoxin B₁: tryptophan (1:1) were found to be 0.64 and 22.6 liters per mole, respectively. The results suggest that charge-transfer interaction occurs between aflatoxin B₁ and these π-electron donors. Since the spectral changes on aflatoxin B₁ absorption induced by these π-electron donors are similar to those induced by nucleic acids and proteins, it is postulated that charge-transfer interaction also occurs between aflatoxin B₁ and these macromolecules. The role of such interaction in the biological activity of aflatoxin B₁ is discussed.     

Effect of Elastic Network of Ceramic Fillers on Thermal Cycle Stability of a Solid Oxide Fuel Cell Stack

Glass‐based seals for planar solid‐oxide fuel‐cell (SOFC) stacks are open to uncontrolled deformation and mechanical damages, limiting both sealing integrity and stack reliability, particularly in thermal cycle operations. If the glass‐based seals work like an elastomer‐based compressive seal, SOFC stacks may survive unprecedented numbers of thermal cycles. A novel composite sealing gasket is successfully developed to mimic the unique features of the elastomer‐based compressive seal by controlling the composition and packing behavior of binary ceramic fillers. A single‐cell SOFC stack undergoes more than 100 thermal cycles with little performance loss, during which the sealing integrity is lost/recovered repeatedly upon cooling and reheating, corresponding to unloading/loading of the elastomer‐based compressive seal. The thermal‐cycle responses of the SOFC stack are explained in sequence by the concurrent events of elastic deformation/recovery of ceramic filler network and corresponding redistribution of sealing glass.     

Biocatalytic potential of laccase-like multicopper oxidases from Aspergillus niger

Background

The integration of biotechnology into chemical manufacturing has been recognized as a key technology to build a sustainable society. However, the practical applications of biocatalytic chemical conversions are often restricted due to their complexities involving the unpredictability of product yield and the troublesome controls in fermentation processes. One of the possible strategies to overcome these limitations is to eliminate the use of living microorganisms and to use only enzymes involved in the metabolic pathway. Use of recombinant mesophiles producing thermophilic enzymes at high temperature results in denaturation of indigenous proteins and elimination of undesired side reactions; consequently, highly selective and stable biocatalytic modules can be readily prepared. By rationally combining those modules together, artificial synthetic pathways specialized for chemical manufacturing could be designed and constructed.

Results

A chimeric Embden-Meyerhof (EM) pathway with balanced consumption and regeneration of ATP and ADP was constructed by using nine recombinant E. coli strains overproducing either one of the seven glycolytic enzymes of Thermus thermophilus, the cofactor-independent phosphoglycerate mutase of Pyrococcus horikoshii, or the non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase of Thermococcus kodakarensis. By coupling this pathway with the Thermus malate/lactate dehydrogenase, a stoichiometric amount of lactate was produced from glucose with an overall ATP turnover number of 31.

Conclusions

In this study, a novel and simple technology for flexible design of a bespoke metabolic pathway was developed. The concept has been testified via a non-ATP-forming chimeric EM pathway. We designated this technology as “synthetic metabolic engineering”. Our technology is, in principle, applicable to all thermophilic enzymes as long as they can be functionally expressed in the host, and thus would be potentially applicable to the biocatalytic manufacture of any chemicals or materials on demand.

     

Existence of sodium bicarbonate enhanced bioelectricity generation on Chlorella sp. biofilm in a Biophotovoltaic (BPV) system

Journal of Applied Phycology - Sodium bicarbonate (NaHCO3) is a low-cost inorganic carbon source, highly soluble in water and widely used in microalgae research. Using carbon dioxide (CO2) gas in...