Bioethanol is mainly produced from food crops such as sugar cane and maize, and this has been held partly responsible for the rise of food commodity prices. Tobacco, integrated in biorefinery ...facilities for the extraction of different compounds, could become an alternative feedstock for biofuel production. When grown for energy production, using high plant densities and several mowings during the growing season, tobacco can produce large amounts of inexpensive green biomass. We have bred two commercial tobacco cultivars (Virginia Gold and Havana 503B) to increase the carbohydrate content by the overexpression of thioredoxin f in the chloroplast. Marker-free transplastomic plants were recovered and their agronomic performance under field conditions was evaluated. These plants were phenotypically equivalent to their wild types yet showed increased starch (up to 280 %) and soluble sugar (up to 74 %) contents in leaves relative to their control plants. Fermentable sugars released from the stalk were also higher (up to 24 %) for transplastomic plants. After heat pretreatment, enzymatic hydrolysis and yeast fermentation of leaf and stalk hydrolysates, an average of 20–40 % more ethanol was obtained from transplastomic plants than their wild-type controls. We propose an integral exploitation of the entire tobacco plant managed as a forage crop (harvesting sugar and starch-rich leaves and lignocellulosic stalks) that could considerably cheapen the entire production process.
To date, one asparagine synthetase (
AS) mRNA has been identified in
Nicotiana tabacum. Our results point out that this gene encodes an actual AS protein. This proposal is supported by the following ...facts. (i) Blast analysis indicates that tobacco
AS gene shows increased percent identity with several
AS genes of different plant species. (ii) Leaf and root
AS mRNA levels were inversely correlated with soluble carbohydrate concentrations, both in the presence of light and in darkness, and the addition of exogenous sucrose repressed the root
AS gene expression. (iii) In light, a positive correlation between
AS transcript levels and ammonium content was observed in both leaves and roots. (iv) A direct correlation between leaf
AS gene expression and asparagine (Asn) concentration has been found. Furthermore, quantitative real-time PCR analyses showed that this gene expression was increased under boron (B) deficiency in roots, but not in leaves. Interestingly, soluble B concentration in roots of plants subjected to B deficiency was significantly lower than that of control plants. However, in leaves, there was no significant difference in soluble B content between both B treatments. We discuss the possible role of soluble B deficiency in the regulation of
AS gene expression in tobacco roots.
Fruit and vegetable (FV) consumption is linked to sensitivity to the bitter compound 6-n-propylthiouracil (PROP). Detection of bitter and sweet compounds is guided by common physiological pathways. ...This study aimed to test whether phenotypic variations in sucrose detection threshold were related to FV consumption. It was predicted that sucrose detection threshold (SDT) would be negatively correlated with FV consumption, and that it would affect preference for FV with high/low carbohydrate content. Thirty eight 5–9 year old children (20 males, 18 females), recruited from local primary schools, were tested. First a triangle test was used to determine sucrose detection threshold. Next, rank order fruit test of 5 fruits that represent different carbohydrate groups was carried out. The results show no significant relationship between SDT and parental reports of portions of fruit and vegetables consumed during the previous 7 days. A liking index, representing preference for sweetness of fruit in the fruit rank test, was calculated. ANOVA showed a significant difference between children with low, medium and high SDT in their preference for different fruits (F(2, 35)=3.254, p=0.05). Post-hoc comparisons using Fisher LSD test revealed that children with low SDT prefer sweeter fruits compared to children with high SDT (p=0.016). This suggests that children who can detect sucrose at low concentrations can better differentiate between different concentrations of carbohydrates in fruits and show natural preference for the sweeter products. Children with low detection threshold may not be able to differentiate between fruits based on their carbohydrate content and make fruit choice based on other factors.
Huitlacoche galls were produced in 15 creole maize genotypes harvested at two stages of development, 23 and 28
days after inoculation, and in a hybrid genotype harvested at six stages of development. ...Raw and cooked galls were evaluated for proximate constituents, carbohydrate composition and antimutagenic activity. Huitlacoche grown in creole maize exhibited differences in concentrations of some of the proximate and carbohydrate components, due to genotype and stage of development; some effects were also observed in hybrid maize, as a result of stage of development and cooking. Huitlacoche has a considerable amount of crude protein (9.8% average in creole maizes, and 11.3% in hybrid maize). Most of the values for total dietary fibre, β-glucans, and total free sugars were higher than those reported for other edible mushrooms. The high concentration of antimutagenic substances appears to be an asset of this culinary delicacy.
A transporter with homology to the SUT/SUC family of plant sucrose transporters was isolated from a sugarcane (Saccharum hybrid) stem cDNA library. The gene, designated ShSUT1, encodes a protein of ...517 amino acids, including 12 predicted membrane-spanning domains and a large central cytoplasmic loop. ShSUT1 was demonstrated to be a functional sucrose transporter by expression in yeast. The estimated K(m) for sucrose of the ShSUT1 transporter was 2 mM at pH 5.5. ShSUT1 was expressed predominantly in mature leaves of sugarcane that were exporting sucrose and in stem internodes that were actively accumulating sucrose. Immunolocalization with a ShSUT1-specific antiserum identified the protein in cells at the periphery of the vascular bundles in the stem. These cells became lignified and suberized as stem development proceeded, forming a barrier to apoplasmic solute movement. However, the movement of the tracer dye, carboxyfluorescein from phloem to storage parenchyma cells suggested that symplasmic connections are present. ShSUT1 may have a role in partitioning of sucrose between the vascular tissue and sites of storage in the parenchyma cells of sugarcane stem internodes.
Honey for Nutrition and Health: A Review Bogdanov, Stefan; Jurendic, Tomislav; Sieber, Robert ...
Journal of the American College of Nutrition,
12/2008, Letnik:
27, Številka:
6
Journal Article
Due to the variation of botanical origin honey differs in appearance, sensory perception and composition. The main nutritional and health relevant components are carbohydrates, mainly fructose and ...glucose but also about 25 different oligosaccharides. Although honey is a high carbohydrate food, its glycemic index varies within a wide range from 32 to 85, depending on the botanical source. It contains small amounts of proteins, enzymes, amino acids, minerals, trace elements, vitamins, aroma compounds and polyphenols. The review covers the composition, the nutritional contribution of its components, its physiological and nutritional effects. It shows that honey has a variety of positive nutritional and health effects, if consumed at higher doses of 50 to 80 g per intake.
Mesophilic and thermophilic strains, active producers of cellulose and xylanase have been isolated from the col- lection available at the Institute. From selected strains three strains, active ...producers of cellulase/xylanase – Peni- cillium canescence Aj13 (mesophile), Trichoderma viride I 7-5 (mesophile), Aspergillus versicolor D1 (thermo- phile) were taken for further studies. It has been shown that Penicillium canescence Aj13, Trichoderma viride I. 7-5 and Aspergillus versicolor D1, selectively chosen strains, representatives of different genera of microscopic fungi hydrolyzed cellulose of untreated stubble to reducing sugars by 36-42% and to glucose – 22-27% and that of treated stubble to reducing sugars by 42-51% and to glucose – 29-33%. Optimal conditions for hydrolysis of stubble cellulose by obtained enzymatic preparations have been established. It was shown that high yield of glu- cose as a result of hydrolysis by enzymatic preparations of thermophilic strain was achieved at higher temperature (over 10°C, under the conditions of 60°C) in comparison of their mesophilic analogues.
Himalaya 292 is a novel hull-less barley cultivar with lower total starch content, a higher proportion of amylose and a substantially higher content of soluble and insoluble fibre. The high fibre ...content suggests that the grain may have potential as an ingredient in health promoting foods. In this study, 29 healthy volunteers consumed extruded whole grain breakfast cereal made from
Himalaya 292 (123
g) or a commercial hull-less barley (cv
Torrens) (76
g) each supplying 50
g carbohydrate. Glycemic indices were 77
±
13 (SEM) and 50
±
9 for
Torrens and
Himalaya 292 breakfast cereals respectively (
P
=
0.004). On this basis, the
Himalaya 292 cereal is a low glycemic index food. The glycemic load (the product of glycemic index and the available carbohydrate content of a 60
g serve divided by 100) of the new cultivar was 10.1
±
1.8 compared to 25.3
±
4.3 for the
Torrens breakfast cereal (
P
<
0.001). The plasma insulin response to the test meal was 26% lower for
Himalaya 292 than for
Torrens (
P
=
0.023). The data confirm that
Himalaya 292 may be of value in foods designed to assist in the prevention and management of diabetes.
In sorghum, brown midrib (bmr) 6 and 12 impair the last two steps of monolignol synthesis. bmr genes were introduced into grain sorghum to improve the digestibility of lignocellulosic tissues for ...grazing or bioenergy uses following grain harvest. Near-isogenic grain sorghum hybrids (AWheatland × RTx430) were developed containing bmr6, bmr12, and the bmr6 bmr12 double mutant (stacked), and their impacts were assessed in a two-year field study. The bmr genes did not significantly impact grain or lignocellulosic tissue yield. Lignocellulosic tissue from bmr6, bmr12, and stacked hybrids had reduced lignin content and increased in vitro dry matter digestibility (IVDMD) compared to those of the wild type (WT). The lignin content of the stacked lignocellulosic tissue was further reduced compared to that of bmr6 or bmr12. Surprisingly, bmr12 modestly increased carbohydrates in lignocellulosic tissue, and bmr6 increased fiber and lignin content in grain. These data indicate that bmr6 and bmr12 have broader effects on plant composition than merely lignin content, which has promising implications for both livestock utilization and bioenergy conversion.
Fructans are the reserve carbohydrates in Agave spp. plants. In mezcal factories, fructans undergoes thermal hydrolysis to release fructose and glucose, which are the basis to produce this spirit. ...Carbohydrate content determines the yield of the final product, which depends on plant organ, ripeness stage, and thermal hydrolysis. Thus, a qualitative and quantitative characterization of nonstructural carbohydrates was conducted in raw and hydrolyzed juices extracted from Agave salmiana stems and leaves under three ripeness stages. By high-performance liquid chromatography (HPLC), fructose, glucose, sucrose, xylose, and maltose were identified in agave juice. Only the plant fraction with hydrolysis interaction was found to be significant in the glucose concentration plant. Interactions of the fraction with hydrolysis and ripeness with hydrolysis were statistically significant in fructose concentration. Fructose concentration rose considerably with hydrolysis, but only in juice extracted from ripe agave stems (early mature and castrated). This increase was statistically significant only with acid hydrolysis.
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