Extracellular microbial polysaccharides: Generalized power law for biopolysaccharide solutions

A generalized power low model, \documentclass{article}\pagestyle{empty}\begin{document}$ \eta \, = \,\eta _0 [1\, + \,(\dot \gamma /\gamma _0 )];{N - 1} $\end{document}, is shown to described satisfactorily the shear viscosity data for xanthan gum solutions from 0.18 g/L to nearly 4 g/L and low to intermediate shear rates. Since mixing, mass and heat transfer, residence time distributions, and power input for agitation and aeration all depend on shear viscosity, this equation provides a simple prediction of this important quantity over the shear rate ranges characteristic of fermentations.     

Kinetics of multiproduct fermentations

A simple model for biomass, product, and substrate evolution proposed previously for batch polysaccharide fermentations is extended to multiproduct fermentations. The examples involve Clostridium thermocellum, (ATCC 27405) fermentations of glucose to four products (ethanol, acetic, formic, and lactic acid), of fructose to two products (ethanol and acetic acid), and of cellobiose to two products (ethanol and acetic acid). In all cases, parameter evaluation was carried out in a serial deterministic procedure.     

Vestitol and vesticarpan,isoflavonoids from Machaerium vestitum

The wood of Machaerium vestitum contains the previously described O-acetyloleanolic aldehyde, formononetin, (+)-medicarpin, and (?)-mucronulatol, besides (+)-vestitol [(3S)-7,2′-dihydroxy-4-methoxyisoflavan] and (+)-vesticarpan [(6aS,11aS)-3,10-dihydroxy-9-methoxypterocarpan]. The constitutions of vestitol and vesticarpan were deduced by spectra and confirmed by syntheses.     

Periodic operation of immobilized cell systems: analysis

The authors' mathematical model of transient immobilized cell growth and product formation is applied here to examine the performance of an immobilized cell system subject to periodic cycling of the rate-limiting substrate supply. The model system consists of a single hydrogel-like (porous) particle entrapping viable microorganisms. Proper nutrient cycling is shown to yield a relaxed periodic system and to virtually eliminate the leakage of biomass from the support that is commonly observed experimentally in steady (continuous nutrient supply) operation of these systems. The use of cyclic operation is evaluated by calculating the average product yield (the ratio of product formed to substrate consumed) and the average product flux from the particle (a measure of the total productivity of the system), for various cycling rates. Cycling increased the average product yield by at least a factor of three in nongrowth-related fermentations, relative to steady operation, without any significant sacrifice in average total productivity. Growth-related fermentations lost significant total productivity under most cycling conditions, while the average product yield was approximately unchanged at all cycling rates. Thus, immobilization in conjunction with periodic operation should be considered as an alternative process design for the production of nongrowth-related products such as penicillin and monoclonal antibodies.     

Pterocarpans from Dalbergia spruceana

The wood of Dalbergia spruceana contains, besides O-acetyloleanolic acid, elemicin and 3,4,5-trimethoxy-cinnamaldehyde; the neoflavonoids (S)-4-methoxydalbergione and dalbergin; the isoflavones biochanin-A, formononetin, pseudobaptigenin and caviunin; and the pterocarpans (±)-medicarpin, (±)-maackiain, as well as the 3,4-dihydroxy-, 3-hydroxy-4-methoxy- and 4-hydroxy-3-methoxy-derivatives of (6aR,11aR)-8,9-methylenedioxypterocarpan. The constitutions of the three last named compounds were deduced by spectra and confirmed by synthesis of (±)-4-hydroxy-3-methoxy-8,9-methylenedioxypterocarpan.     

Diffusion influences in denaturable insolubilized enzyme catalysts

The influence of diffusion on the apparent thermal stability of a reversibly or irreversibly denaturable enzyme is examined theoretically when he enzyme is uniformly distributed in a porous solid. If the overall reaction rate is influenced by diffusion through the catalyst, the insolubilized catalyst is shown to yield an apparently more thermally stable enzyme even though the maximal velocity V_m, and the Michaelis constant, K_m, are the same for the free and insolubilized forms of enzyme. Brief consideration is given to the experimental conditions needed to clearly demonstrate whether insolubilization does or does not effect the thermal stability of the enzyme.     

Development of affinity chromatography-aided radioactive assay of monoclonal antibody

Summary A new method for measuring MAb synthesis rate, Affinity Chromatography-aided Radioactive Assay of MAb (ACRA) was developed. ACRA shortened the time period for measuring MAb synthesis rate to 6 hours vs. the 8 days required for the conventional radioactive labeling assay of MAb. ACRA is able to measure MAb synthesis rate with an accuracy much better than ELISA in many cases; it could become a tool advantageously useful for studying MAb production kinetics.     

Violastyrene and isoviolastyrene,cinnamylphenols from Dalbergia miscolobium

The heartwood of Dalbergia miscolobium contains, in addition to the neoflavonoids (S)-4-methoxydal-bergione, (S)-4′-hydroxy-4-methoxydalbergione and dalbergin, the isoflavone di-O-methyldaidzein, the benzophenone cearoin and two cinnamylphenols, violastyrene [E-1-(3-hydroxy-2,4-dimethoxybenzyl)-2-phenylethylene] and isoviolastyrene [E-1-(4-hydroxy-2,3-dimethyoxybenzyl)-2-phenylethylene]. The structural determination of the cinnamylphenols relied on spectra, degradations and synthesis.