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Applied Biochemistry and Biotechnology: Part A: Enzyme Engineering and Biotechnology (v.82, #1)
Solid-state fermentation of lignocellulosic plant residues from Brassica napus by Pleurotus ostreatus by Ayda Sarikaya; Michael R. Ladisch (pp. 1-15).
Solid-state fermentation (SSF) of inedible parts of rapeseed was carried out using a white-rot fungus, Pleurotus ostreatus, to degrade lignocellulosic material for mycelial-single cell protein (SCP) production. This SSF system has the potential to be adapted to a controlled ecological life support system in space travel owing to the lack of storage space. The system for converting lignocellulosic material to SCP by P. ostreatus is simple; it can be carried out in a compact reactor. The fungal vegetative growth was better with a particle size of plant material ranging from 0.42 to 10 mm, whereas lignin degradation of the lignocellulose was the highest with particle sizes ranging from 0.42 to 0.84 mm. The addition of veratry alcohol (3,4-dimethoxybenzyl alcohol), hydrogen peroxide, and glycerol promotes lignocellulose degradation by P. ostreatus. The enhancement of bioconversion was also observed when a gas-flow bioreactor was used to supply oxygen and to maintain the constant moisture of the reactor. With this reactor, approx 85% of the material was converted to fungal and other types of biomass after 60 d of incubation.
Keywords: Lignocellulose; controlled ecological life support system; biodegradation; Pleurotus ostreatus ; solid-state fermentation
Assessment of various carbon sources and nutrient feeding strategies for Panax ginseng cell culture by Jianyong Wu; Kwok-ping Ho (pp. 17-26).
Ginseng (root of Panax ginseng C. A. Meyer) cells were cultivated on medium supplemented with various carbohydrates including sucrose, glucose, and fructose, at initial concentrations ranging from 10 to 110 g/L. Sucrose was shown to be the superior carbon source to the monosaccharides for ginseng cell growth and the optimal concentration was between 30 and 50 g/L. An increase in the initial concentration within this range increased the maximum cell density and growth index significantly, whereas much higher concentrations inhibited cell growth. Feeding of sucrose and some other medium components during the growth (fed-batch mode) was more effective in enhancing the cell growth and biomass productivity, increasing the growth index by more than 60–70% and biomass productivity by more than 50%.
Keywords: Biomass productivity; carbon source; nutrient feeding; Panax ginseng ; plant cell culture; sugar concentration
Application of factorial design to the optimization of peroxidase activity in reverse micelles of bis(2-ethylhexyl)sodium sulfosuccinate/isooctane by Ana Morna-Gomes; Maria Luisa Serralheiro; Pedro Salema Fevereiro; Maria Raquel Aires-Barros (pp. 27-36).
Two cationic peroxidases isolated from Vaccinium myrtillus were encapsulated in reverse micelles of bis(2-ethylhexyl)sodium sulfosuccinate/isooctane. By using a central composite design, some relevant parameters for the enzymatic activity, such as surfactant and water concentration, pH, and buffer molarity, were analyzed. With the results obtained from this experimental planning, the response surface curves were established. The maximum specific activity obtained (0.19 mM/min · mM of enzyme) was approximately the same for both peroxidases, but the experimental conditions under which this value was attained differed considerably.
Keywords: Peroxidase; reverse micelles; activity; factorial design; response surface
Enzyme self-inactivation is a main limitation of the preparation of eicosanoids by Stanislav I. Shram; Tatyana Yu. Lazurkina; Nikolay F. Myasoyedov; Sergey D. Varfolomeyev (pp. 37-56).
Synthesis of prostanoids is accompanied by various processes reducing the product yield. These processes are also known to affect syntheses of thromboxane (TX) and 12(S)-hydroxy-5(Z),8(Z),10(E),14(Z)-eicosatetraenoic acid (12-HETE). Partially purified preparations of TX synthase and prostaglandin (PG) synthase were used to optimize TX synthesis with respect to concentrations of the enzymes and eicosapolyenoic acid (EPA). Conditions for the maximum product yield and the minimum consumption of enzymes were determined. Consumption of the TX synthase was large owing to its inactivation during the reaction and the nonenzymatic destruction of the intermediate product PG-endoperoxide. Separate addition of PG and TX synthases increased the product yield by preventing EPA sorption on ballast proteins. Microsomal 12-lipoxygenase (12-LO) was also shown to be inactivated during the reaction, and this process was the major limitation of 12-HETE synthesis. Lipoxygenase reaction in the presence of some reducing agents led to a considerable increase of the 12-HETE yield, supposedly by preventing further oxidation of the 12-LO reaction product 12-hydroperoxy derivative of eicosatetraenoic acid. The possibility of using human blood platelet microsomes for preparation of some derivatives of EPAs is discussed.
Keywords: Eicosanoids; thromboxane; 12-HETE; prostaglandin synthase; thromboxane synthase; 12-lipoxygenase; biosynthesis; enzyme self-inactivation
Modification of the electrokinetic properties of reversible electrophoresis gels for the separation and preparation of DNA by Kenneth D. Cole; Carlos M. Tellez; Richard B. Nguyen (pp. 57-76).
The effect of adding linear polymers to a novel reversible electrophoretic media was measured. Reversible gels are formed using the polyanionic carbohydrate polymer, gellan gum. Gellan gum forms strong stable gels in the presence of divalent cations or diamines. The gels are reversible (return to solution) by changing the ionic environment or pH. Gellan gum is an anionic polymer, and the electrophoresis gels have considerable electroosmotic flow (EOF) toward the negative electrode. We measured the EOF in gellan gum electrophoresis gels as a function of gel concentration, buffer composition, and linear polymer additive. The linear polymers used in this study were polyethylene oxide and hydroxyethyl cellulose. Both polymers reduced EOF in the gels, in a manner dependent on molecular weight. Polymers with high molecular weight were more effective at reducing EOF. The addition of polymers increased the resolution of low molecular weight DNA. Native gellan gum resolved DNA from approx 50,000 to 1000 bp. Addition of the polymers resolved DNA down to approx 50 bp, in some instances. The influence of the polymers on circular plasmid DNA was also investigated. Addition of high molecular weight polyethylene oxide reduced the electrophoretic mobility of the nicked circular form compared to the supercoiled form.
Keywords: Electrophoresis gel; DNA; electroosmosis; separation; reversible; preparative; gellan gum