Functional analysis on sucrose transporters in sweet potato / 生物工程学报

Sweet potato is an important food crop that can also be used as an industrial raw material. Sucrose is the main form of long-distance carbohydrate transport in plants, and sucrose transporter (SUT) regulates the transmembrane transport and distribution of sucrose during plant growth and metabolism. Moreover, SUT plays a key role in phloem mediated source-to-sink sucrose transport and physiological activities, supplying sucrose for the sink tissues. In this study, the full-length cDNA sequences of IbSUT62788 and IbSUT81616 were obtained by rapid amplification of cDNA ends (RACE) cloning according to the transcripts of the two SUT coding genes which were differentially expressed in sweet potato storage roots with different starch properties. Phylogenetic analysis was performed to clarify the classification of IbSUT62788 and IbSUT81616. The subcellular localization of IbSUT62788 and IbSUT81616 was determined by transient expression in Nicotiana benthamiana. The function of IbSUT62788 and IbSUT81616 in sucrose and hexose absorption and transport was identified using yeast functional complementarity system. The expression pattern of IbSUT62788 and IbSUT81616 in sweet potato organs were analyzed by real-time fluorescence quantitative PCR (RT-qPCR). Arabidopsis plants heterologous expressing IbSUT62788 and IbSUT81616 genes were obtained using floral dip method. The differences in starch and sugar contents between transgenic and wild-type Arabidopsis were compared. The results showed IbSUT62788 and IbSUT81616 encoded SUT proteins with a length of 505 and 521 amino acids, respectively, and both proteins belonged to the SUT1 subfamily. IbSUT62788 and IbSUT81616 were located in the cell membrane and were able to transport sucrose, glucose and fructose in the yeast system. In addition, IbSUT62788 was also able to transport mannose. The expression of IbSUT62788 was higher in leaves, lateral branches and main stems, and the expression of IbSUT81616 was higher in lateral branches, stems and storage roots. After IbSUT62788 and IbSUT81616 were heterologously expressed in Arabidopsis, the plants grew normally, but the biomass increased. The heterologous expression of IbSUT62788 increased the soluble sugar content, leaf size and 1 000-seed weight of Arabidopsis plants. Heterologous expression of IbSUT81616 increased starch accumulation in leaves and root tips and 1 000-seed weight of seeds, but decreased soluble sugar content. The results obtained in this study showed that IbSUT62788 and IbSUT81616 might be important genes regulating sucrose and sugar content traits in sweet potato. They might carry out physiological functions on cell membrane, such as transmembrane transport of sucrose, sucrose into and out of sink tissue, as well as transport and unloading of sucrose into phloem. The changes in traits result from their heterologous expression in Arabidopsis indicates their potential in improving the yield of other plants or crops. The results obtained in this study provide important information for revealing the functions of IbSUT62788 and IbSUT81616 in starch and glucose metabolism and formation mechanism of important quality traits in sweet potato.

Advances in heterologous expression, structural elucidation and molecular modification of pullulanase / 生物工程学报

Starch is composed of glucose units linked by α-1, 4-glucoside bond and α-1, 6-glucoside bond. It is the main component of foods and the primary raw material for starch processing industry. Pullulanase can effectively hydrolyze the α-1, 6-glucoside bond in starch molecules. Combined with other starch processing enzymes, it can effectively improve the starch utilization rate. Therefore, it has been widely used in the starch processing industry. This paper summarized the screening of pullulanase-producing strain and its encoding genes. In addition, the effects of expression elements and fermentation conditions on the production of pullulanase were summarized. Moreover, the progress in crystal structure elucidation and molecular modification of pullulanase was discussed. Lastly, future perspectives on pullulanase research were proposed.

Amylase from Bacillus sp. Produced by Solid State Fermentation Using Cassava Bagasse as Starch Source

Abstract Amylases are enzymes involved in starch hydrolysis, generating the most diverse products, such as maltose, glucose and dextrins. This work aimed the study of the production of amylolytic enzymes via solid-state fermentation (SSF) using "crueira", an essentially starchy cassava residue, as substrate-support and Bacillus sp. as microorganism. For the implementation of the experimental part, a Central Composite Design (CCD) with three variables (initial moisture, pH and temperature) was made. Each test was examined at 24, 48 and 72 hours by the method of starch dextrinizing activity. The optimum production conditions were 60% initial moisture, pH 6 and 37 °C. The maximum yield was 437.76 U/g in 72 hours of fermentation. The optimum temperature of enzyme performance was 65 °C. The pH optimum range was 4 to 6. The Co2 +, Ca2 + and K+ ions positively influenced the activity of enzymes and the Fe2+ ion had no effect on enzymatic activity. On the other hand, the ions Hg2+, Zn2+, Cu2+, Mn2+ and Mg2+ adversely influenced enzymatic activity. Therefore, producing amylases from Bacillus sp. and using crueira as a substrate is possible.

Digestibilidade do amido e comportamento ingestivo de novilhos confinados sob efeito de doses de complexo enzimático em dietas de alta densidade energética / Digestibility of starch and ingestive behavior of feedlot steers by effect of enzymatic complex doses in high-energy diets

O objetivo do presente trabalho foi avaliar a conversão alimentar, a digestibilidade do amido, o comportamento ingestivo e o escore de sobras da dieta e de fezes de novilhos confinados, suplementados com doses do complexo enzimático (0; 2,5; 5,0 e 7,5g animal-1 dia-1) e alimentados com dieta constituída por 85% de grão de milho e 15% de núcleo proteico, vitamínico e mineral, na base seca, isenta de forragem. O delineamento experimental foi o de blocos ao acaso contendo quatro tratamentos e quatro repetições. Trinta e dois novilhos inteiros, ½ sangue Angus Nelore, com idade média de 12 meses e peso vivo médio inicial de 422kg, foram confinados por um período de 77 dias. Cada grama de inclusão de complexo enzimático melhorou a conversão alimentar em 0,1652%, reduziu a matéria seca das fezes em 0,4648% e o tempo de ingestão de água em 0,0068 horas dia-1. A máxima digestibilidade do amido foi alcançada na dose de 5,08g animal-1 dia-1. A inclusão progressiva do complexo enzimático à dieta de alta densidade energética promoveu melhoria na conversão alimentar, redução na matéria seca das fezes e diminuição do tempo de ingestão de água. A dose de 5g animal-1 dia-1 do complexo enzimático aumentou a digestibilidade do amido.(AU)

The objective was to evaluate the feed conversion, starch digestibility, ingestive behavior, diet leftover score and feces score of steers supplemented with doses of enzyme complex (0; 2.5; 5.0 and 7 .5g animal -1 day -1 ) fed with roughage-free diet composed of a mixture of 85% whole corn grain and 15% protein-mineral-vitamin mix, on a dry matter basis. A completely randomized block design was adopted, consisting of four treatments and four replicates. Thirty-two ½ Angus ½ Nellore crossbred steers at an average age of 12 months, with an average initial weight of 422kg, were kept in a feedlot for 77 days. Each gram of enzyme complex inclusion improved feed conversion in 0.1652%, decreased feces dry matter in 0,4648% and time of water intake in 0.0068 hours day -1 . The maximum starch digestibility was reached in the dose of 5,08g animal -1 day -1 . The gradual inclusion of enzyme complex promoted improvement in feed conversion, reduction in the dry matter of feces and redution in the time of water intake. The enzyme complex dose of 5.0g animal -1 day -1 increased the starch digestibility.(AU)

Selection of starter cultures for the production of sour cassava starch in a pilot-scale fermentation process

ABSTRACT Sour cassava starch (Polvilho azedo) is obtained from a spontaneous fermentation conducted by microorganisms from raw materials and fermentation tanks. This product is traditionally used in the baking industry for the manufacture of biscuits and Brazilian cheese breads. However, the end of fermentation is evaluated empirically, and the process occurs without standardization, which results in products of inconsistent quality. Predominant microbiota from a cassava flour manufacturer was isolated in order to select starter cultures for the production of sour cassava starch in a pilot-scale fermentation process. Lactic acid bacteria and yeasts were isolated, enumerated and grouped by Restriction Fragment Length Polymorphism, and PCR fingerprinting, respectively. One isolate of each molecular profile was identified by sequencing of the rRNA gene. LAB were prevalent throughout the entire process. Lactobacillus brevis (21.5%), which produced the highest values of acidity, and Lactobacillus plantarum (13.9%) were among the most frequent species. Pichia scutulata (52.2%) was the prevalent yeast and showed amylolytic activity. The aforementioned species were tested as single and mixed starter cultures in a pilot-scale fermentation process for 28 days. L. plantarum exhibited better performance as a starter culture, which suggests its potential for the production of sour cassava starch.

Evaluation of short-chain-length polyhydroxyalkanoate accumulation in Bacillus aryabhattai

Abstract This study was focused on the polyhydroxybutyrate (PHB) accumulation property of Bacillus aryabhattai isolated from environment. Twenty-four polyhydroxyalkanoate (PHA) producers were screened out from sixty-two environmental bacterial isolates based on Sudan Black B colony staining. Based on their PHA accumulation property, six promising isolates were further screened out. The most productive isolate PHB10 was identified as B. aryabhattai PHB10. The polymer production maxima were 3.264 g/L, 2.181 g/L, 1.47 g/L, 1.742 g/L and 1.786 g/L in glucose, fructose, maltose, starch and glycerol respectively. The bacterial culture reached its stationary and declining phases at 18 h and 21 h respectively and indicated growth-associated PHB production. Nuclear Magnetic Resonance (NMR) spectra confirmed the material as PHB. The material has thermal stability between 30 and 140 °C, melting point at 170 °C and maximum thermal degradation at 287 °C. The molecular weight and poly dispersion index of the polymer were found as 199.7 kDa and 2.67 respectively. The bacterium B. aryabhattai accumulating PHB up to 75% of cell dry mass utilizing various carbon sources is a potential candidate for large scale production of bacterial polyhydroxybutyrate.

Highly efficient enzymatic preparation of isomalto-oligosaccharides from starch using an enzyme cocktail

Background: Current commercial production of isomalto-oligosaccharides (IMOs) commonly involves a lengthy multistage process with low yields. Results: To improve the process efficiency for production of IMOs, we developed a simple and efficient method by using enzyme cocktails composed of the recombinant Bacillus naganoensis pullulanase produced by Bacillus licheniformis, α-amylase from Bacillus amyloliquefaciens, barley bran ß-amylase, and α-transglucosidase from Aspergillus niger to perform simultaneous saccharification and transglycosylation to process the liquefied starch. After 13 h of reacting time, 49.09% IMOs (calculated from the total amount of isomaltose, isomaltotriose, and panose) were produced. Conclusions: Our method of using an enzyme cocktail for the efficient production of IMOs offers an attractive alternative to the process presently in use.

Efficient production of pullulan by Aureobasidium pullulans grown on mixtures of potato starch hydrolysate and sucrose

Abstract Pullulan is a natural exopolysaccharide with many useful characteristics. However, pullulan is more costly than other exopolysaccharides, which limits its effective application. The purpose of this study was to adopt a novel mixed-sugar strategy for maximizing pullulan production, mainly using potato starch hydrolysate as a low-cost substrate for liquid-state fermentation by Aureobasidium pullulans. Based on fermentation kinetics evaluation of pullulan production by A. pullulans 201253, the pullulan production rate of A. pullulans with mixtures of potato starch hydrolysate and sucrose (potato starch hydrolysate:sucrose = 80:20) was 0.212 h−1, which was significantly higher than those of potato starch hydrolysate alone (0.146 h−1) and mixtures of potato starch hydrolysate, glucose, and fructose (potato starch hydrolysate:glucose:fructose = 80:10:10, 0.166 h−1) with 100 g L−1 total carbon source. The results suggest that mixtures of potato starch hydrolysate and sucrose could promote pullulan synthesis and possibly that a small amount of sucrose stimulated the enzyme responsible for pullulan synthesis and promoted effective potato starch hydrolysate conversion effectively. Thus, mixed sugars in potato starch hydrolysate and sucrose fermentation might be a promising alternative for the economical production of pullulan.

Feasibility of biohydrogen production from industrial wastes using defined microbial co-culture

BACKGROUND: The development of clean or novel alternative energy has become a global trend that will shape the future of energy. In the present study, 3 microbial strains with different oxygen requirements, including Clostridium acetobutylicum ATCC 824, Enterobacter cloacae ATCC 13047 and Kluyveromyces marxianus 15D, were used to construct a hydrogen production system that was composed of a mixed aerobic-facultative anaerobic-anaerobic consortium. The effects of metal ions, organic acids and carbohydrate substrates on this system were analyzed and compared using electrochemical and kinetic assays. It was then tested using small-scale experiments to evaluate its ability to convert starch in 5 L of organic wastewater into hydrogen. For the one-step biohydrogen production experiment, H1 medium (nutrient broth and potato dextrose broth) was mixed directly with GAM broth to generate H2 medium (H1 medium and GAM broth). Finally, Clostridium acetobutylicum ATCC 824, Enterobacter cloacae ATCC 13047 and Kluyveromyces marxianus 15D of three species microbial co-culture to produce hydrogen under anaerobic conditions. For the two-step biohydrogen production experiment, the H1 medium, after cultured the microbial strains Enterobacter cloacae ATCC 13047 and Kluyveromyces marxianus 15D, was centrifuged to remove the microbial cells and then mixed with GAM broth (H2 medium). Afterward, the bacterial strain Clostridium acetobutylicum ATCC 824 was inoculated into the H2 medium to produce hydrogen by anaerobic fermentation. RESULTS: The experimental results demonstrated that the optimum conditions for the small-scale fermentative hydrogen production system were at pH 7.0, 35°C, a mixed medium, including H1 medium and H2 medium with 0.50 mol/L ferrous chloride, 0.50 mol/L magnesium sulfate, 0.50 mol/L potassium chloride, 1% w/v citric acid, 5% w/v fructose and 5% w/v glucose. The overall hydrogen production efficiency in the shake flask fermentation group was 33.7 mL/h-1.L-1, and those the two-step and the one-step processes of the small-scale fermentative hydrogen production system were 41.2 mLVh-1.L-1 and 35.1 mL/h-1.L-1, respectively. CONCLUSION: Therefore, the results indicate that the hydrogen production efficiency of the two-step process is higher than that of the one-step process.

Single nucleotide polymorphisms in partial sequences of the gene encoding the large sub-units of ADP-glucose pyrophosphorylase within a representative collection of 10 Musa genotypes

Background ADP-glucose pyrophosphorylase (AGPase) is a rate-limiting enzyme catalyzing the first step in the starch biosynthesis pathway in higher plants. To date, there are no reported variants or isoforms of the AGPase enzyme in bananas (Musa spp. family Musaceae) as is the case of other plants. In this study, genomic DNA sequences homologous to the gene encoding one of the large subunits of the enzyme were amplified from 10 accessions of the genus Musa, including representatives of wild ancestors (AA and BB genomes), dessert bananas (AA, AAA, AB and AAB genomes), plantains (AAB genome) and cooking bananas (ABB and AAA genomes), and studied in order to find single nucleotide polymorphisms (SNP) base variations in Musa accessions. Results In the 810-base pair amplicons of the AGPase large sub-unit (LSU) gene analyzed in ten Musa accessions, a total of 36 SNPs and insertions/deletions (indels) were found. The phylogenetic analysis revealed fifteen distinct haplotypes, which were grouped into four variants. Deep examination of SNPs in the 2nd exon in the LSU of AGPase showed that at seven locations, five SNPs altered their amino acid sequence. Conclusions This work reveals the possible number of AGPase enzyme isoforms and their molecular levels in banana. Molecular markers could be designed from SNPs present in these banana accessions. This information could be useful for the development of SNP-based molecular markers for Musa germplasm, and alteration of the allosteric properties of AGPase to increase the starch content and manipulate the starch quality of banana fruits.

Characterization of differentially expressed stress-associated proteins in starch granule development under heat stress in wheat (Triticum aestivum L.).

Abiotic stress causes abrupt increase in the expression of stress-associated proteins, which provide tolerance by modulating the defense mechanism of plants. Small heat shock proteins (sHSPs) and anti-oxidant enzymes are important for environmental stress tolerance of the plants. In this study, two full-length cDNAs encoding small heat shock protein (sHSP) and superoxide dismutase (SOD), designated as TasHSP and SODI were identified and characterized from C-306 (thermotolerant) and PBW343 (thermosusceptible) cultivars of wheat (Triticum aestivum L.). An alpha crystalline domain was observed in TasHSP and manganese/iron binding domain in case of SODI. Quantitative real-time PCR showed very high transcript level of TasHSP and SOD in C-306 compared to PBW343 at different stages of growth and against differential heat stress (HS). Under differential HS at milky-dough stage, the fold change in transcript of both TasHSP and SOD was observed maximum in C-306, compared to PBW343. Protein profiling and isoenzymes analysis showed the expression of several heat-stable proteins and prominent isoenzymes of SOD in C-306, compared to PBW343. Scanning electron microscopy (SEM) of starch granules showed globular, well-shaped and more numbers of endospermic cells in C-306, compared to defragmented, irregular shaped and shrunken granules in case of PBW343 under HS treatment (42°C for 2 h). Diurnal change in soluble starch synthase (SSS) activity showed an increase in the activity during afternoon (35°C), compared to morning (29°C) and evening (32°C) in both the cultivars. Under heat stress (42°C for 2 h), a drastic decrease in the SSS activity was observed, due to the thermal denaturation of the enzyme. Thermotolerance capacity analyzed using cell membrane stability (CMS) showed significantly higher CMS in case of C-306, compared to PBW343 at different stages of growth. Findings suggest that abundance of TasHSP and SODI during milky-dough stage plays a very important role in starch granule biosynthesis. The mechanism may be further exploited to develop tolerant wheat cultivar with high quality seeds.

Biodegradation of a blended starch/natural rubber foam biopolymer and rubber gloves by Streptomyces coelicolor CH13

Background: The growing problem of environmental pollution caused by synthetic plastics has led to the search for alternative materials such as biodegradable plastics. Of the biopolymers presently under development, starch/natural rubber is one promising alternative. Several species of bacteria and fungi are capable of degrading natural rubber and many can degrade starch. Results: Streptomyces coelicolor CH13 was isolated from soil according to its ability to produce translucent halos on a mineral salts medium, MSM, supplemented with natural rubber and to degrade starch. Scanning electron microscope studies showed that it colonized the surfaces of strips of a new starch/natural rubber biopolymer and rubber gloves and caused degradation by forming holes, and surface degradation. Starch was completely removed and polyisoprene chains were broken down to produce aldehyde and/or carbonyl groups. After 6 weeks of cultivation with strips of the polymers in MSM, S. coelicolor CH13 reduced the weight of the starch/NR biopolymer by 92 percent and that of the rubber gloves by 14.3 percent. Conclusions: This study indicated that this bacterium causes the biodegradation of the new biopolymer and natural rubber and confirms that this new biopolymer can be degraded in the environment and would be suitable as a ‘green plastic’ derived from natural sources.

Glycaemic & insulinaemic responses in men at rest following sago meal.

Background & objective: Sago (Metroxylin sagu) is one of the main sources of native starch. In Malaysia sago dishes are commonly eaten with sugar. However, other societies use sago as a staple food item instead of rice or potato. The study was undertaken to investigate the effect of ingestion of different physical forms of sago supplementation on plasma glucose and plasma insulin responses, as compared to the white bread supplementation in man, during resting condition. Methods: Twelve male subjects were given in random order with three different physical forms of a sago supplementation, viz., sago porridge (SR), sago paste (SP), sago gel (SG) and white bread (WB) which was repeated on separate days, at least, 1 wk apart after an overnight fast. Venous blood samples were collected at baseline and at 15, 30, 45, 60, 90, 120, 150 and 180 min after the start of each meal and were analyzed for plasma levels of glucose and insulin. Results: Plasma glucose reached peak at 45 min after supplementation of various sago meals. Plasma glucose area under the curve (AUC) for WB was significantly lower than SG but not significantly different from SR and SP. No significant difference was observed in plasma glucose AUC among the three sago meals. Plasma insulin AUC for SG was significantly higher than WB and SR. All three sago meals tested were not significantly different in their glycaemic responses. However, the insulin response was significantly lower for SR compared to SP and SG. Interpretation & conclusions: The present findings suggest that any one of the three sago meals tested in this study may be used to elucidate the effect of sago starch ingestion on exercise performance in the heat. Sago paste and sago porridge may be used for supplementation before and during exercise, whereas, sago gel may be used after endurance exercise during recovery process.

Ocorrência e biossíntese de frutooligossacarídeos em banana / Occurrence and biosynthesis of fructooligosaccharides in banana

A banana tem sido comumente indicada como uma boa fonte de frutooligossacarídeos (FOS), que são considerados componentes funcionais de alimentos. Contudo, diferenças significantes em suas quantidades têm sido referidas na literatura. Portanto, uma parte do trabalho foi destinada à identificação e quantificação de FOS durante o amadurecimento de cultivares de bananas pertencentes aos grupos genômicos mais comumente cultivados no Brasil. Considerando as diferencas de cultivar, estágio do amadurecimento e metodologia usada para análise de FOS, os conteúdos dos acúcares foram analisados por cromatografia líquida de alta performance (HPAEC-PAD) e cromatografia a gás (CG-MS). Uma pesquisa inicial entre oito cultivares no estágio maduro, mostrou acúmulo de 1-cestose, primeiro membro da série de FOS, em todas elas (quantidades entre 297 e 1600 ´MUg/g M. S´). A nistose, o segundo membro, foi detectado somente no cultivar Prata. Com bases nestes dados, foram escolhidas cinco cultivares, para que fossem analisadas durantes todo o amadurecimento. Os resultados mostraram uma forte correlação entre a síntese de 1-cestose e um nível específico de sacarose (~200mg/g M.S)...

Caracterização funcional do gene maBMY que codifica para uma `BETA´-amilase endereçada a plastídeos e expressa durante o amadurecimento da banana / Functional characterization of maBMY gene that encodes a `BETA´-amylase targeted to plastids and expressed during banana ripening

O amadurecimento dos frutos é um processo caracterizado pela ocorrência de diversas alterações bioquímicas que ocorrem em um curto intervalo de tempo e que são importantes para a qualidade desses alimentos. Na banana uma das características mais importantes é o adoçamento do fruto, que ocorre como resultado da degradação do amido e acúmulo de sacarose. Resultados do nosso grupo apontam a ´BETA` amilase como uma enzima importante no processo de mobilização do amido, o que também é visto em estudos recentes utilizando Arabidopsis thaliana como modelo, os quais mostram que a principal via de degradação do amido transitório presente nas folhas ocorre pela ação da ´BETA`-amilase. Entretanto, em bananas, faltam evidências quanto à funcionalidade de um gene de ´BETA`amilase, parcialmente isolado da polpa do fruto, e que é expresso durante o amadurecimento e que parece ser modulado por hormônios vegetais. Em vista disso, esse trabalho objetivou realizar a caracterização funcional desse gene, a qual permitiu constatar que esse gene codifica, de fato, para uma proteína capaz de ser endereçada aos cloroplastos. Também foi observado que o promotor desse gene contém motivos regulatórios para os mesmos hormônios previamente relacionados com a modulação da expressão desse gene em bananas. Essas novas evidências reforçam a idéia de que o produto desse gene de ´BETA`amilase tem um importante papel no processo de degradação do amido durante o amadurecimento da banana...

Relación entre la respuesta glicémica del almidón y su estado microestructural / Relationship between glycemic response of starch and its microstructural state

Se ha observado que alimentos que contienen almidón en cantidades similares pueden generar respuestas glicémicas diferentes. En este trabajo se realizó una revisión bibliográfica tendiente a estudiar uno de los factores que modelaría estas diferencias: el estado físico del almidón contenido en el alimento. Los resultados expuestos indican que el estado físico (que llamaremos microestructura) del almidón es uno de los factores principales a considerar, ya que determinaría cómo y qué fracción del total será digerida, lo cual a su vez determina cómo y cuánto será absorbido para su uso metabólico. Estudios tendientes a una mejor cuantificación, tanto de la microestructura como de la respuesta glicémica y efectos fisiológicos, parecen ser necesarios si se tiene como objetivo el poder diseñar alimentos que cumplan con requerimientos nutricionales específicos.

It has been observed that foods with similar amount of starch can generate different glycemic responses. In the present paper we review the one factor that probably determines these differences: the physical state of starch in food. The literature support the idea that the physical state (called microstructure) of starch is a very important factor because determine the rate and the total amount of glucose that will be released (in the digestion process) for absorption and metabolic use. Many studies relating the microstructure and glycemic response, and its physiological effects, are still needed to make new carbohydrate foods with specific nutritional requirements.

Solid substrate fermentation of cassava fibrous residue for production of alpha-amylase, lactic acid and ethanol.

There is serious concern about the disposal of solid residues left after large scale extraction of starch from cassava. Owing to the high starch content (55-65% on dry weight basis) and organic matter of these wastes, an attempt has been made to utilize it for the production of three bioproducts, i.e. alpha-amylase, lactic acid and ethanol in solid substrate fermentation by incubating the solid residue at different moisture holding capacity (40-80%) and incubation period (12- 60 hr for alpha-amylase, 24-144 hr for ethanol and 2-10 days for lactic acid). The highest product yield was obtained at 60% moisture holding capacity of the residue and period of incubation varied from 36 hr (alpha-amylase), 120 hr (ethanol) to 6 days (lactic acid). This study showed that the solid residues from cassava starch factories could serve as a low-cost substrate for bioproducts production.

Relationship between structural and biochemical characteristics and texture of corn grains

The texture of corn grains is a fundamental characteristic for the industry as well as for grain producers and processors. To further understand the mechanisms involved in grain hardness, contrasting corn cultivars for grain hardness and protein quality were evaluated. The cultivars were Cateto L237/67 (hard endosperm and low protein value), QPM BR 451 (semi-hard endosperm and high protein value); Bolivia-2 (floury endosperm and low protein value), and Opaque-2 (floury endosperm and high protein value). Evaluations were carried out at 10, 20, 30, 40, 50, and 60 days after pollination in developing corn grains and in the mature grain. In developing grains, evaluation consisted in the determination of the area, percentage of starch granules, distribution of starch granules, and protein bodies in the endosperm. In mature corn grains, the parameters evaluated were: density, percentage of total proteins, levels of lysine and tryptophan, and banding pattern of zeins. The results indicate that the higher physical resistance of corn grains from the cultivars analyzed is influenced by the high percentage of total proteins, high synthesis of 27-kDa zeins, presence of protein bodies, and perfect organization of starch granules in the endosperm, independent of their sizes.

Anatomical alterations due to polyploidy in cassava, Manihot esculenta Crantz

Information on anatomical structure is needed by breeders working on improvement for drought tolerance. For studying the effect of polyploidy on cassava anatomy and its significance to tolerance to drought, we induced a polyploidy type of a selected clone (UnB 530) by applying an aqueous solution of 0.2% colchicine on lateral buds for a period of 12 h. The stem identified as tetraploid was propagated to produce the whole plant. Free-hand cross-sections of the median portion between stem internodes were made. They were clarified using 50% sodium hypochlorite solution, stained with 1% safranin-alcian blue, passed through an ethanol series and butyl acetate and mounted in synthetic resin. The tetraploid type showed more prismatic and druse crystals in the cortical parenchyma, and its pericycle fibers had thicker walls. The secondary xylem of tetraploid types was wider than diploid ones, having thinner walls and less starch.

O efeito do 1-metilciclopropeno o metabolismo de carboidratos de bananas (Musa acuminata AAA cv. Nanicão) / The effect of 1-methylcyclopropene on bananas (Musa acuminata AAA cv. Nanicão

A banana é um fruto climatérico que apresenta alta taxa respiratória e alta produção de etileno após a colheita, o que a torna altamente perecível. Acredita-se que o 1-MCP é capaz de ligar-se ao receptor do hormônio etileno, bloqueando sua ação e, conseqüentemente, retardando o amadurecimento do fruto. Bananas (Musa acuminata AAA cv. Nanicão) com aproximadamente 110 dias pós-antese foram armazenadas em condições controladas de umidade e temperatura. Parte da amostra foi tratada com 1-MCP (100 nl/L, outra parte foi tratada com etileno (100 ppm – 7L/min), e, uma terceira parte, foi mantida como controle. Os frutos foram caracterizados, durante o período de amadurecimento, em relação à produção de etileno e C`O IND. 2’ (por cromatografia à gás) , à concentração de amido (pelo método enzimático descrito por Cordenunsi e Lajolo 1995) e açúcares (glicose, frutose, sacarose e maltose – por HPLC-PAD). Também foram analisados os comportamentos das enzimas α e ß – amilases, fosforilase, DPE 1 e DPE 2 por atividade enzimática in vitro ou por P.A.G.E. nativo e, quando possível, foram avaliados os comportamentos destas enzimas frente a tradução (Western blotting) e transcrição protéica (Northern blotting). A degradação de amido, assim como a respiração, a produção de etileno e síntese de açúcares foram retardadas nos frutos tratados com o 1-MCP. Como conseqüência destas mudanças, também houve uma alteração nos perfis das atividades enzimáticas...