Gas-liquid as well as gas-liquid-solid bubble column reactors are extensively used in the chemical industry. This review evaluates the present state of the art for the estimation of “nonadjustable” parameters in bubble column reactors. All the pertinent literature concerning these parameters is discussed and the discussion is followed by relevant recommendations for their predictions. Literature on the modified bubble columns has been incorporated. Finally, the inadeqacies of the data in some areas of practical importance have been pointed out and the recommendations for future work are outlined.

Design parameters estimations for bubble column reactors

Starvation for amino acids induces Gcn4p, a transcriptional activator of amino acid biosynthetic genes in Saccharomyces cerevisiae. In an effort to identify all genes regulated by Gcn4p during amino acid starvation, we performed cDNA microarray analysis. Data from 21 pairs of hybridization experiments using two different strains derived from S288c revealed that more than 1,000 genes were induced, and a similar number were repressed, by a factor of 2 or more in response to histidine starvation imposed by 3-aminotriazole (3AT). Profiling of a gcn4Δ strain and a constitutively induced mutant showed that Gcn4p is required for the full induction by 3AT of at least 539 genes, termed Gcn4p targets. Genes in every amino acid biosynthetic pathway except cysteine and genes encoding amino acid precursors, vitamin biosynthetic enzymes, peroxisomal components, mitochondrial carrier proteins, and autophagy proteins were all identified as Gcn4p targets. Unexpectedly, genes involved in amino acid biosynthesis represent only a quarter of the Gcn4p target genes. Gcn4p also activates genes involved in glycogen homeostasis, and mutant analysis showed that Gcn4p suppresses glycogen levels in amino acid-starved cells. Numerous genes encoding protein kinases and transcription factors were identified as targets, suggesting that Gcn4p is a master regulator of gene expression. Interestingly, expression profiles for 3AT and the alkylating agent methyl methanesulfonate (MMS) overlapped extensively, and MMS induced GCN4 translation. Thus, the broad transcriptional response evoked by Gcn4p is produced by diverse stress conditions. Finally, profiling of a gcn4Δ mutant uncovered an alternative induction pathway operating at many Gcn4p target genes in histidine-starved cells.

Transcriptional Profiling Shows that Gcn4p Is a Master Regulator of Gene Expression during Amino Acid Starvation in Yeast

The biosynthesis of bacterial cell wall peptidoglycan is a complex process that involves enzyme reactions that take place in the cytoplasm (synthesis of the nucleotide precursors) and on the inner side (synthesis of lipid-linked intermediates) and outer side (polymerization reactions) of the cytoplasmic membrane. This review deals with the cytoplasmic steps of peptidoglycan biosynthesis, which can be divided into four sets of reactions that lead to the syntheses of (1) UDP-N-acetylglucosamine from fructose 6-phosphate, (2) UDP-N-acetylmuramic acid from UDP-N-acetylglucosamine, (3) UDP-N-acetylmuramyl-pentapeptide from UDP-N-acetylmuramic acid and (4) D-glutamic acid and dipeptide D-alanyl-D-alanine. Recent data concerning the different enzymes involved are presented. Moreover, special attention is given to (1) the chemical and enzymatic synthesis of the nucleotide precursor substrates that are not commercially available and (2) the search for specific inhibitors that could act as antibacterial compounds.

Cytoplasmic steps of peptidoglycan biosynthesis.

The phenomenon of dispersion (transverse and longitudinal) in packed beds is summarized and reviewed for a great deal of information from the literature. Dispersion plays an important part, for example, in contaminant transport in ground water flows, in miscible displacement of oil and gas and in reactant and product transport in packed bed reactors. There are several variables that must be considered, in the analysis of dispersion in packed beds, like the length of the packed column, viscosity and density of the fluid, ratio of column diameter to particle diameter, ratio of column length to particle diameter, particle size distribution, particle shape, effect of fluid velocity and effect of temperature (or Schmidt number). Empirical correlations are presented for the prediction of the dispersion coefficients (D
 T and D
 L) over the entire range of practical values of Sc and Pem, and works on transverse and longitudinal dispersion of non-Newtonian fluids in packed beds are also considered.

https://paginas.fe.up.pt/~jdelgado/2006_HMT__JD.pdf

A critical review of dispersion in packed beds

Redox reactions are important steps in the metabolism and energy conversion of living cells. Besides the enzymes necessary, a number of coenzymes are involved in such reactions: ferrodoxins, lipoic acid, NAD(H), NADP(H), flavins and cytochromes. The coenzymes differ in their redox potential, in the binding constants and the mode of regeneration [1]. NADH/NADPH are the most frequently encountered coenzymes. In general they dissociate easily and need a second reaction with another metabolite for regeneration. These properties are one of the means by which nature directs the flow of intermediates in response to biosynthetic needs. Because of the spectral properties of the coenzyme moiety, dehydrogenases have been extensively studied in the past [2] and have found widespread applications in clinical and food analysis [3].

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1989.tb14983.x

Dehydrogenases for the synthesis of chiral compounds

高粘性流体や非ニュートン流体の混合には槽内全体に上下循環流を強制せしめる翼が有効である。混合能力の秀れた翼として案内円筒付半楕円板翼, 案内円筒付スクリュー翼, リボンとスクリェーの組み合せ翼, および2枚羽根対称取り付けのリボン翼が見い出された。リボンの軸部にスクリューを取り付けることによって混合能力の向上が得られるが, スクリューによる送り出し液量がリボンのそれより小なる際には混合能力は低下する。

Mixing of Highly Viacoua non-Newtonian Liquids

We found an inducible NADP+ -dependent D-phenylserine dehydrogenase in a soil bacterium identified as Pseudomonas syringae NK-15. The enzyme catalyzed the oxidation of the 3-hydroxyl group of D-threo-3-phenylserine to yield D-2-amino-3-keto-3-phenylpropionate, which was spontaneously decarboxylated into 2-aminoacetophenone. The enzyme had an optimum reactivity at about pH 10.4. The Km for D-threo-3-phenylserine and NADP+ were 0.44 mM and 29 μM, respectively.

Occurrence of an Inducible NADP+ -Dependent D-Phenylserine Dehydrogenase in Pseudomonds syringae NK-15 Isolated from Soil

We discovered a D-phenylserine deaminase that catalyzed the pyridoxal 5'-phosphate (PLP)-dependent deamination reaction from D-threo-phenylserine to phenylpyruvate in newly isolated Arthrobacter sp. TKS1. The enzyme was partially purified, and its N-terminal amino acid sequence was analyzed. Based on the sequence information, the gene encoding the enzyme was identified and expressed in Escherichia coli. The expressed protein was purified to homogeneity and characterized. The enzyme consisted of two identical 46-kDa subunits and showed maximum activity at pH 8.5 and 55°C. The enzyme was stable in the range of pH 7.5 to pH 8.5 and up to 50°C. The enzyme acted on the D-forms of β-hydroxy-α-amino acids, such as D-threo-phenylserine (K(m), 19 mM), D-serine (K(m), 5.8 mM), and D-threonine (K(m), 102 mM). As L-threonine, D-allo-threonine, L-allo-threonine, and DL-erythro-phenylserine were inert, the enzyme could distinguish D-threo-form from among the four stereoisomers of phenylserine or threonine. The enzyme was activated by ZnSO(4), CuSO(4), BaCl(2), and CoCl(2) and strongly inhibited by phenylhydrazine, sodium borohydride, hydroxylamine, and DL-penicillamine. The enzyme exhibited absorption maxima at 280 and around 415 nm. The enzyme has an N-terminal domain similar to that of alanine racemase, which belongs to the fold type III group of pyridoxal enzymes.

Discovery and characterization of D-phenylserine deaminase from Arthrobacter sp. TKS1.

Effect of cracked rice on Ginjou-shu brewing

Method of Measuring Power Consumption by Mixing Impellers

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