An improved method for disruption of microbial cells with pressurized carbon dioxide.

Disruption of microbial cells by pressurized carbon dioxide at both subcritical and supercritical temperatures has been previously investigated. This method differs in principle from other disruption techniques and was found to have potential applications for rupture of a variety of microorganisms. However, it is not as effective for some of the microbial cells, including yeast, of which the cell walls are extremely robust and rigid. This work suggests an alternative operation to improve the disruption rates of cells by repeatedly releasing the applied fluid pressure within the cells in the midst of a disruption process. The improvement is substantial at all the experimental conditions studied.     

Modelling as a tool of enzyme reaction engineering for enzyme reactor development

Strategy of the development of model for enzyme reactor at laboratory scale with respect to the modelling of kinetics is presented. The recent literature on the mathematic modelling on enzyme reaction rate is emphasized.     

Formation of inclusion complexes between cyclodextrins and aromatic compounds under pressurized carbon dioxide

The effects of moisture content, pressure and temperature on the formation of inclusion complexes with cyclodextrins under pressurized carbon dioxide (CO₂) were studied to determine the optimal conditions for the recovery of aromatic compounds after extraction with supercritical or liquid CO₂. The presence of water in the cyclodextrin was essential for the formation of inclusion complex. However, an excess of water lowered the amount of inclusion complex due to inhibition of contact with CO₂. As the pressure increased under a constant temperature, the amount of inclusion complex increased until CO₂ became liquid, where the formation of inclusion complex started to decline. The amount of inclusion complex for modified cyclodextrins was very little, because the cyclodextrins became paste- or candy-like by the addition of a small amount of water.     

Supercritical carbon dioxide explosion as a pretreatment for cellulose hydrolysis

Summary Cellulosic material Avicel was treated with supercritical carbon dioxide to increase the reactivity of cellulose, thereby to enhance the rate and the extent of cellulose hydrolysis. Upon an explosive release of the carbon dioxide pressure, the disruption of the cellulosic structure increases the accessible surface area of the cellulosic substrate to enzymatic hydrolysis. This explosion pretreatment enhances the rate of the Avicel hydrolysis as well as increases glucose yield by as much as 50%.     

Over-expression of carbon monoxide dehydrogenase-I with an accessory protein co-expression: a key enzyme for carbon dioxide reduction

Carbon monoxide dehydrogenase-I (CODH-I) from the CO-utilizing bacterium Carboxydothermus hydrogenoformans are expected to be utilized as a part of reproducible carbon dioxide photoreduction system. However, the over-expression system for CODH-I remains to be constructed. CODH-I constitutes a hydrogenase/CODH gene cluster including a gene encoding a Ni-insertion accessory protein, CooC (cooC3). Through co-expression of CooC3, we found an over-expression system with higher activity. The Rec-CODH-I with the co-expression exhibits 8060?U/mg which was approximately threefold than that without co-expression (2270?U/mg). In addition, co-expression resulted in Ni²⁺ content increase; the amount of Ni atoms of Rec-CODH-I was approximately thrice than that without co-expression.     

False-negative oxidase reaction as a result of medium acidification

Acidification of the culture medium may lead to a false-negative result of the oxidase reaction. Hence, if the medium contained a carbon source or another component that is convertible to acid, a negative oxidase reaction should be considered inconclusive. In order to eliminate false-negative reactions, a reagent freshly adjusted to pH 5–7 might be used; this reagent should be checked on known oxidase-negative strains. However, we recommend that the oxidase test be performed with the normal reagent after (sub)culturing on a non-acidogenic medium.     

Ionic liquids as a reaction medium for lipase-catalyzed methanolysis of sunflower oil

Ionic liquids, 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIm][PF₆]) and 1-ethyl-3-methyl imidazolium hexafluorophosphate ([EMIm][PF₆]), were used for the methanolysis of sunflower oil using Candida antarctica lipase (Novozyme 435) and gave yields of fatty acid methyl esters at 98–99% within 10 h. The optimum conditions of methanolysis in hydrophobic ionic liquids are 2% (w/w) lipase, 1:1 (w/w) oil/ionic liquid and 1:8 (mol/mol) oil/methanol at 58–60°C. Methanolysis using hydrophilic ionic liquids, 3-methyl imidazolium tetrafluoroborate ([HMIm][BF₄]) and 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIm][BF₄]), gave very poor yields. A hydrophobic ionic liquid thus protects the lipase from methanol. Recovered ionic liquids and lipase were used for four successive reaction cycles without any significant loss of activity.     

Regulatory role of carbon dioxide in malate dehydrogenase reaction

The reaction rate catalyzed by NAD-dependent malate dehydrogenase is studied as affected by carbon dioxide. It is shown that acceleration of the catalysis in this system depends on the presence of both a bicarbonate anion and solved carbon dioxide.     

The characterization of a pectin-degrading enzyme from Aspergillus oryzae grown on passion fruit peel as the carbon source and the evaluation of its potential for industrial applications

An extracellular pectinase (PEC-I) was isolated from the crude extract of Aspergillus oryzae when grown on passion fruit peel (PFP) as the carbon source and partially purified by ultra filtration, gel filtration and ion-exchange chromatography procedures. Pectinase activity was predominantly found in the retentate. The pectinase from retentate (PEC-Ret) was most active at 50?°C and pH 7.0 and stable at 50?°C with a half-life of approximately 8?h. PEC-I showed higher activity at pH 4.5 and 55?°C, 70?°C and 75?°C and was inhibited by cations (Ag⁺, Fe²⁺, Fe³⁺, Co²⁺, Ca²⁺ and Hg²⁺), EDTA, tannic acid and vanillin. On the other hand, PEC-I was activated by Cu²⁺, ferulic acid, cinnamic acid and 4-hydroxybenzoic acid. The gel under denaturing conditions of PEC-Ret and PEC-I samples showed a protein band of ～45?kDa coincident with that found by staining for pectinase activity. In the bioscouring of cotton fabric the PEC-Ret pectinase preparation led to a better wettability and removed more pectin from the cotton fibers than the commercial enzyme preparation Viscozyme L, but was less effective than a commercial alkaline pectate lyase preparation and alkaline scouring. The incubation of PEC-Ret with guava juice resulted in a 4.15% decrease in juice viscosity.     

Effects of medium composition and carbon dioxide on circadian conidiation in neurospora

Efforts to significantly perturb the timing mechanism, and thus the period, of the rhythm responsible for circadian conidiation in bd, a strain of Neurospora crassa, by altering the medium composition have been unsuccessful. Various salt solutions, sugars, and amino acids do, however, have pronounced effects on growth and conidiation, and thus on the expression and persistence of rhythmicity.