1.
The use of microorganisms in L-ascorbic acid production.
Bremus, C, Herrmann, U, Bringer-Meyer, S, Sahm, H
Journal of biotechnology. 2006;(1):196-205
Abstract
L-Ascorbic acid has been industrially produced for around 70 years. Over the past two decades, several innovative bioconversion systems have been proposed in order to simplify the long time market-dominating Reichstein method, a largely chemical synthesis by which still a considerable part of L-ascorbic acid is produced. Here, we describe the current state of biotechnological alternatives using bacteria, yeasts, and microalgae. We also discuss the potential for direct production of l-ascorbic acid exploiting novel bacterial pathways. The advantages of these novel approaches competing with current chemical and biotechnological processes are outlined.
2.
Biosafety considerations for selectable and scorable markers used in cassava (Manihot esculenta Crantz) biotechnology.
Petersen, W, Umbeck, P, Hokanson, K, Halsey, M
Environmental biosafety research. 2005;(2):89-102
Abstract
Cassava is an important subsistence crop grown only in the tropics, and represents a major source of calories for many people in developing countries. Improvements in the areas of resistance to insects and viral diseases, enhanced nutritional qualities, reduced cyanogenic content and modified starch characteristics are urgently needed. Traditional breeding is hampered by the nature of the crop, which has a high degree of heterozygosity, irregular flowering, and poor seed set. Biotechnology has the potential to enhance crop improvement efforts, and genetic engineering techniques for cassava have thus been developed over the past decade. Selectable and scorable markers are critical to efficient transformation technology, and must be evaluated for biosafety, as well as efficiency and cost-effectiveness. In order to facilitate research planning and regulatory submission, the literature on biosafety aspects of the selectable and scorable markers currently used in cassava biotechnology is surveyed. The source, mode of action and current use of each marker gene is described. The potential for toxicity, allergenicity, pleiotropic effects, horizontal gene transfer, and the impact of these on food or feed safety and environmental safety is evaluated. Based on extensive information, the selectable marker genes nptII, hpt, bar/pat, and manA, and the scorable marker gene uidA, all have little risk in terms of biosafety. These appear to represent the safest options for use in cassava biotechnology available at this time.
3.
Metabolic redesign of vitamin E biosynthesis in plants for tocotrienol production and increased antioxidant content.
Cahoon, EB, Hall, SE, Ripp, KG, Ganzke, TS, Hitz, WD, Coughlan, SJ
Nature biotechnology. 2003;(9):1082-7
Abstract
Tocotrienols are the primary form of vitamin E in seeds of most monocot plants, including cereals such as rice and wheat. As potent antioxidants, tocotrienols contribute to the nutritive value of cereal grains in human and livestock diets. cDNAs encoding homogentisic acid geranylgeranyl transferase (HGGT), which catalyzes the committed step of tocotrienol biosynthesis, were isolated from barley, wheat and rice seeds. Transgenic expression of the barley HGGT in Arabidopsis thaliana leaves resulted in accumulation of tocotrienols, which were absent from leaves of nontransformed plants, and a 10- to 15-fold increase in total vitamin E antioxidants (tocotrienols plus tocopherols). Overexpression of the barley HGGT in corn seeds resulted in an increase in tocotrienol and tocopherol content of as much as six-fold. These results provide insight into the genetic basis for tocotrienol biosynthesis in plants and demonstrate the ability to enhance the antioxidant content of crops by introduction of an enzyme that redirects metabolic flux.