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Applied Biochemistry and Biotechnology: Part A: Enzyme Engineering and Biotechnology (v.116, #1-3)
Session 6B Plant biotechnology and feedstock genomics
by James S. McLaren; Steven R. Thomas (pp. 1163-1165).
Expression of UDP-glucose dehydrogenase reduces cell-wall polysaccharide concentration and increases xylose content in alfalfa stems by Deborah A. Samac; Lynn Litterer; Glena Temple; Hans-Joachim G. Jung; David A. Somers (pp. 1167-1182).
The primary cell-wall matrix of most higher plants is composed of large amounts of uronic acids, primarily d-galacturonic acid residues in the back-bone of pectic polysaccharides. Uridine diphosphate (UDP)-glucose dehydrogenase is a key enzyme in the biosynthesis of uronic acids. We produced transgenic alfalfa (Medicago sativa) plants expressing a soybean UDP-glucose dehydrogenase cDNA under the control of two promoters active in alfalfa vascular tissues. In initial greenhouse experiments, enzyme activity in transgenic lines was up to seven-fold greater than in nontransformed control plants; however, field-grown transgenic plants had only a maximum of 1.9-fold more activity than the control. Cell-wall polysaccharide content was lower and Klason lignin content was higher in transgenics compared to the nontransformed control. No significant increase in pectin or uronic acids in the polysaccharide fraction was observed in any line. Xylose increased 15% in most transgenic lines and mannose concentration decreased slightly in all lines. Because of the complexity of pectic polysaccharides and sugar biosynthesis, it may be necessary to manipulate multiple steps in carbohydrate metabolism to alter the pectin content of alfalfa.
Keywords: Carbohydrate; forage; homogalacturonan; lucerne; protein utilization
Effects of ammonia fiber explosion treatment on activity of endoglucanase from Acidothermus cellulolyticus in transgenic plant by Farzaneh Teymouri; Hasan Alizadeh; Lizbeth Laureano-Pérez; Bruce Dale; Mariam Sticklen (pp. 1183-1191).
A critical parameter affecting the economic feasibility of lignocellulosic bioconversion is the production of inexpensive and highly active cellulase enzymes in bulk quantity. A promising approach to reduce enzyme costs is to genetically transform plants with the genes of these enzymes, thereby producing the desired cellulases in the plants themselves. Extraction and recovery of active proteins or release of active cellulase from the plants during bioconversion could have a significant positive impact on overall lignocellulose conversion economics. The effects of ammonia fiber explosion (AFEX) pretreatment variables (treatment temperature, moisture content, and ammonia loading) on the activity of plant-produced heterologous cellulase enzyme were individually investigated via heat treatmett or ammonia treatment. Finally, we studied the effects of all these variables in concert through the AFEX process. The plant materials included transgenic tobacco plants expressing E1 (endoglucanase from Acidothermus cellulolyticus). The E1 activity was measured in untreated and AFEX-treated tobacco leaves to investigate the effects of the treatment on the activity of this enzyme. The maximum observed activity retention in AFEX-treated transgenic tobacco samples compared with untreated samples was approx 35% (at 60°C, 0.5∶1 ammonia loading, and 40% moisture). Based on these findings, it is our opinion that AFEX pretreatment is not a suitable option for releasing cellulase enzyme from transgenic plants.
Keywords: Ammonia fiber explosion; endoglucanase; Acidothermus cellulolyticus ; transgenic tobacco; E1cd
Effects of inoculum conditions on growth of hairy roots of Panax ginseng C. A. Meyer by Gwi-Taek Jeong; Don-Hee Park; Hwa-Won Ryu; Baik Hwang; Je-Chang Woo (pp. 1193-1203).
Plants have a potential to produce a large number of important metabolites such as pharmaceuticals, food additives, pigments, flavors, fragrances, and fine chemicals. Large-scale plant cell and tissue cultures for producing useful products has been considered an attractive alternative to whole plant extraction for obtaining valuable chemicals. In plant cell and tissue cultures, cell growth and metabolite production are influenced by nutritional and environmental conditions as well as physical properties of the culture system. To obtain a high growth rate of plant cell and tissue cultures, the culture tem. To obtain a high growth rate of plant cell and tissue cultures, the culture conditions should be maintained at an optimum level. We studied the relationship between inoculum conditions and the growth of Panax ginseng hairy root culture, and found that the growth rate varied with the inoculum conditions such as the number of root tips, the length of root tips, the part of root tips, and the inoculum size and age of hairy roots.
Keywords: Panax ginseng ; transformed hairy root; inoculum condition; inoculum age; root culture
Special Session A Microbial pentose metabolism
by Bärbel Hahn-Hägerdal; Neville Pamment (pp. 1207-1209).
Special Session B International energy agency—Bioenergy
by Warren E. Mabee; David J. Gregg; John N. Saddler (pp. 1213-1214).