Cyclodextrins (CDs) are cyclic oligosaccharides containing six (alpha), seven (beta), or eight (gamma) glucose molecules, respectively. The cyclodextrin glycosyltransferases (CGT), which produce CDs from starch, are found only in bacteria and are used in batch fermentors with hydrolyzed starch to produce CDs commercially. Using a CGT gene from Klebsiella, we attempted to engineer the tubers of developing potatoes to produce these novel, high-value carbohydrates. A chimeric gene, consisting of (1) the patatin promoter for tuber-specific expression, (2) the small subunit of ribulose bisphosphate carboxylase (SSU) transit peptide for plastid targeting, (3) the CGT structural gene from Klebsiella and (4) the nopaline synthase 3' region, was introduced into potatoes. Both alpha and beta CDs were produced in tubers of transgenic potatoes at levels corresponding to 0.001-0.01% of the starch being converted to CDs.

Structure and chemical composition of the potato.

Production of cyclodextrins, a novel carbohydrate, in the tubers of transgenic potato plants.

Tuber formation is a well orchestrated physiological event that involves many metabolic changes. Dormancy gradually develops in potato tubers from the moment cell division in the stolon tip has stopped and the tuber starts to develop. Dormancy breakage may be the reverse of dormancy initiation suggesting that there may be similarities between tuber induction and dormancy development. Based on a literature review it is concluded that, when comparing tuber induction and the breaking of dormancy, hormonal activities are only partly reversed, whereas carbohydrates and enzyme activities might be reversed. For more definite conclusions more research should be done to assess precisely the moment of dormancy breaking. Moreover, measurements on events associated with tuber induction and dormancy breaking should be carried out using the same techniques and the same material. Molecular genetic analyses may provide well-defined markers for the timing of breaking of dormancy.

Is dormancy breaking of potato tubers the reverse of tuber initiation

Publisher Summary The total production of potato starch is small compared to the total amount of starch produced in the world. This chapter gives an overview of the total production of starch worldwide focusing on the major commercial modifications of all potato starch reactions and the various uses of potato starch. Most of the dry matter of a potato tuber consists of starch granules. Starch forms the reserve material in the tuber for use in respiration and sprouting. Starch granules are formed from the very early stages of tuberization, as soon as the stolon tip begins to swell. The starch content increases during tuber growth. This increase is caused both by an increase in the number of granules and by enlargement of granule size. The chemical composition of the potato is very important to the potato starch industry. Potato processors must take account of factors such as dry matter, starch, and protein content. To obtain starch from potatoes, one of several processing routes, discussed in the chapter, can be chosen. With the grinding of the potatoes, the cells are broken open and a mixture of starch granules, broken cell walls, and the remainder of the cell content, which is mostly water containing soluble proteins, amino acids, sugars, and salts is formed. For further processing, physical separation of the two solid components (starch and fiber) from each other and from the potato juice is essential. Native potato starch, which is used in the food, paper, and textile industries, is often not optimal for a particular application. Modifications are done to obtain the properties needed for specific uses.

Potato Starch: Production, Modifications and Uses

Under water weight (UWW), specific gravity (SG), dry matter (DM) and starch content of potatoes were determined in tubers grown at Modipuram, Uttar Pradesh. Linear regression equations and correlation coefficients were worked out for different pairs of values. There was a positive correlation between UWW and SG (r=0.99), UWW and DM (r=0.92) and, UWW and starch content (r=0.77). Regression equations for the relationship of UWW with SG, DM and starch content are presented in this paper. Based on these equations, a conversion table has been developed for potatoes grown in North Indian plains, for the benefit of the potato processing industry.

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http://epubs.icar.org.in/ejournal/index.php/PotatoJ/article/viewFile/33346/14775

Conversion table for specific gravity, dry matter and starch content from under water weight of potatoes grown in north-indian plains

Over the last decades rapid developments in potato production and mechanization occurred, aiming to increase capacity and to reduce costs. Concomitantly, potatoes can be damaged more easily. Subcutaneous tissue discolouration, a major quality problem, is a result of mechanical damage and reduces the market value of potatoes considerably. This study focused on the effect of mechanical force on subcutaneous tissue discolouration. The study started with an analysis of representative Dutch ware-potato handling-chains in terms of utilization, produce-friendliness and the subsequent incidence of subcutaneous tissue discolouration. In parallel, forces acting in these chains were quantified. Using an instrumented sphere (IS100) a better understanding of the forces acting in the chain was obtained. It appeared that 78% of the measured impacts occurred during packaging and that 98% of the impacts did not exceed 150 g . The results of the chain analysis were the basis for experiments on dose-effect relations, focused on the effect of repetitive impacts and impact body shape on the occurrence of subcutaneous tissue discolouration. A new computer-controlled pendulum was developed to impact potato tubers at a desired rate. This pendulum proved to be an adequate tool to impact tubers precisely and reproducibly. In particular the effect of repetitive impacts on potato tubers and the effect of the shape (curvature) of both potato and impact body became clear. It appeared that splitting 0.6 J of impact energy over 9 equal impacts reduced the depth and volume of discoloured tissue by 33 and 64%, respectively. Spherical impact bodies, relative to a non-spherical one, doubled the volume and depth of discoloured tissue. The results urge a reappraisal of some commonly accepted insights. For example the effect of low-energetic repetitive impacts on subcutaneous tissue discolouration cannot be neglected. The use of spherical impact bodies has to be minimized. The research suggests important routes for the potato sector to make adequate changes in technique and technology. These changes make it possible to reduce both the number and the intensity of impacts and should result in a produce which can be offered to the consumer in a condition (almost) free of subcutaneous tissue discolouration. When the utilization of machinery is optimized damage reduction may be substantial. Some potential improvements are: better utilization of machinery, better planning of bunker storage, box handling and improved temperature control of the tubers. To further optimize the whole potato handling-chain with respect to produce-friendliness additional research should focus on fundamental knowledge that is currently missing, and on developing an optimal logistic handling concept. Crucial in this concept are flexibility and produce-friendliness. Ideally, potatoes may be transported along different routes and the number and intensity of impacts are minimal. Also repetitive impacts on the same tuber site and the use of spherical impact bodies are avoided. The effect of the time interval between consecutive impacts has to be studied. It should also be elucidated at which curvature spherical impact bodies cause damage. To create a more produce-friendly attitude of growers, and other actors in the potato handling-chain a better differentiation between 'good' and 'poor quality' potatoes is necessary. A financial incentive could have a substantial effect, resulting into potatoes with a high quality, i.e. free of tissue discolouration. This thesis is also available as publication No. 99-14, ISBN 90-5406-180-4 of the Institute of Agricultural and Environmental Engineering (IMAG), P.O. Box 43, NL-6700 AA, Wageningen, The Netherlands

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Structure and chemical composition of the potato.

Citations

Production of cyclodextrins, a novel carbohydrate, in the tubers of transgenic potato plants.

Is dormancy breaking of potato tubers the reverse of tuber initiation

Potato Starch: Production, Modifications and Uses

Conversion table for specific gravity, dry matter and starch content from under water weight of potatoes grown in north-indian plains

Mechanical force and subcutaneous tissue discolouration in potato

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