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See detailEffect of the use of dilute alkaline prior to Bacillus subtilis-based biocontrol steeping and germination conditions on red sorghum malt β-glucanase activities and residual β-glucans
Bwanganga Tawaba, Jean-Claude ULg; Destain, Jacqueline ULg; Malumba Kamba, Paul ULg et al

in Journal of Cereal Science (2013)

Malting is the ideal stage to deal with β-glucans. Their hydrolysis is very important as the diffusion of both hormones and hydrolytic enzymes in the endosperm of germinated grain depend on it. A high ... [more ▼]

Malting is the ideal stage to deal with β-glucans. Their hydrolysis is very important as the diffusion of both hormones and hydrolytic enzymes in the endosperm of germinated grain depend on it. A high malt β-glucanase activity is not a guarantee of an extensive hydrolysis of β-glucans. When Bacillus subtilis is used to control mould growth, red sorghum malt β-glucanase activity (measured using carboxymethylcellulose as the substrate) was improved without significantly affecting the hydrolysis of malt β-glucans. Thus, in order to reduce the residual β-glucans content, soaking in 0.2% NaOH was combined with a biocontrol. Soaking in 0.2% NaOH is recognized as capable of improving grain hydration by opening-up the endosperm cell walls. The combined use of 0.2% NaOH with Bacillus subtilis-based biocontrol treatments during red sorghum malting, leads to malt with increased β-glucanase activity and a significant reduction of residual β-glucans when compared with the 16 h biocontrol steeping without prior steeping in 0.2% NaOH. β-glucanase activity increases with increased germination temperature and time while, conversely, the residual β-glucans content of the malts decreases. Indeed, while the level of β-glucanase was not vastly different between the malts obtained after steeping in distilled water and those obtained after 8 h steeping in 0.2% NaOH followed by 8 h resteeping in distilled water (NaOH+H2O treatment), their residual β-glucans levels differ significantly. Bacillus subtilis-based treatment leads to malt with improved β-(1-3)- and β-(1-4)-glucanase activities without significantly improved malt β-(1-3),(1-4)-glucanase activity. While malts obtained after 84 h germination weren’t significantly different in terms of malt β-(1-3),(1-4)-glucanase activities for all steeping treatments, the use of 0.2% NaOH steeping prior to resteeping led to malts with improved β-glucans content. Combining the steeping in dilute alkaline and biocontrol enables taking advantage of the dilute alkaline effect on residual β-glucans content, due probably to the opening-up the cell walls and the improvement of water uptake, and that of the biocontrol (improvement of β-glucanase synthesis). [less ▲]

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See detailOptimisation de la production de Pseudomonas fluorescens BTP1 en fermenteur.
Mputu Kanyinda, Jean-Noël; Thonart, Philippe ULg

in International Journal of Microbiology Research (2013), 5(1), 370-373

The optimisation of production and freeze-drying of P. fluorescens used as a bio-control agent was investigated. P. fluorescens BTP1 was produced in a bioreactor with different against-pressure value (0.1 ... [more ▼]

The optimisation of production and freeze-drying of P. fluorescens used as a bio-control agent was investigated. P. fluorescens BTP1 was produced in a bioreactor with different against-pressure value (0.1 and 0.3 bar for bioreactor 1 and 2 respectively) and cells were harvested during the stationary phase (2 h and 4 h for bioreactor 1 and 2 respectively). A mixture of protective compounds were tested for freeze-drying, and the highest result was found for glycerol and maltodextrine (26%) followed by glycerol, maltodextrine and ascorbic acid (18.9%) and glycerol with ascorbic acid (8.5%). We observed that the survival rate is better at 4°C than at room temperature and those powders with protective compounds have a survival rate greater than the powder without protective compounds during storage. [less ▲]

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See detailFlow-cytometric assessment of damages to Acetobacter senegalensis during freeze-drying process and storage
Shafiei, Rasoul ULg; Delvigne, Frank ULg; Thonart, Philippe ULg

in Acetic Acid Bacteria (2013), 2(2(s1)), 10

Downstream processes have great influences on bacterial starter production. Different modifications occur to cellular compounds during freeze-drying process and storage of bacterial starters. Consequently ... [more ▼]

Downstream processes have great influences on bacterial starter production. Different modifications occur to cellular compounds during freeze-drying process and storage of bacterial starters. Consequently, viability and culturability (multiplication capacity) undergo some changes. In this study, the effects of freeze-drying process and storage conditions were examined on cell envelope integrity, respiration and culturability of Acetobacter senegalensis. <br />Freezing of cells protected with mannitol (20% w/w) did not affect cell multiplication and respiration considerably; however, 19% of cells showed compromised cell envelope after freezing. After drying, 1.96×1011 CFU/g were enumerated, indicating that about 34% of the <br />cells could survive and keep their culturability. Drying of the cells induced further leakage in cell envelope and finally 81% of cells appeared as injured ones; however, 87% of the dried cells maintained their respiration capacity. Storage temperature had significant effect on cell multiplication ability; higher storage temperature (35°C),caused 8.59-log reduction in cell culturability after nine-month period of storage. Collapse of cell envelop integrity and respiration wasobserved at 35°C. At lower storage temperature (4°C), the culturability <br />decreased about one-log reduction after nine months. Cell envelope integrity was subjected to minor changes during a period of nine month-storage at 4°C whereas a heterogeneous population of cells with different respiration capacity emerged at 4°C. These results indicate that a major part of cells undergone drying process and storage entered into viable but non-culturable state. In addition, usage of different culture media didn’t improve resuscitation. Besides, it seems that sub-lethal damages to cell envelope caused uptake of propidium iodide, however these kinds of injuries could not impress cell multiplications and respiration. [less ▲]

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See detailEvaluation of viability and growth of Acetobacter senegalensis under different stress conditions
Shafiei, Rasoul ULg; Thonart, Philippe ULg; Delvigne, Frank ULg et al

in International Journal of Food Microbiology (2013)

Acetic acid bacteria (AAB) are used in production of vinegars. During acetic acid fermentation, AAB encounter various aggressive conditions which may lead to a variety of cellular disorders. Previous ... [more ▼]

Acetic acid bacteria (AAB) are used in production of vinegars. During acetic acid fermentation, AAB encounter various aggressive conditions which may lead to a variety of cellular disorders. Previous researches mainly studied the influences of different carbon sources on tolerance of AAB to ethanol and acetic acid. In this study, different techniques were used comparatively to investigate the effects of preadaptation on the ability of A. senegalensis to tolerate ethanol and acetic acid. In general, the carbon sources used for preadaptation of A. senegalensis exhibited significant effects on the tolerance of cells to stressors. Flow-cytometric assessments of preadapted cells in ethanol showed that 87.3% of the cells perform respiration after exposure to a stress medium containing 5% (v/v) ethanol and 3% (w/v) acetic acid. However, 58.4% of these preadapted cells could keep their envelope integrity under the stress condition. They could also grow rapidly (μmax = 0.39/h) in the stress medium (E5A3) with a high yield (>80%). A. senegalensis grown in glucose exhibited a low tolerance to acetic acid. Analysis of their respiration capacity, membrane integrity and culturability revealed that almost all the population were dead after exposure to 5% (v/v) ethanol and 3% (w/v) acetic acid. In contrast, exposure of A. senegalensis preadapted in a mixture of glucose and acetic acid to a stress medium containing 5% (v/v) ethanol and 3% (w/v) acetic acid, exhibited an intact respiration system and cellular membrane integrity in 80.3% and 50.01% of cells, respectively. Moreover, just 24% of these cells could keep their culturability under that stress condition. [less ▲]

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See detailOn-line flow cytometry profiling of Escherichia coli stress response
Brognaux, Alison ULg; Han, Shanshan; Sorensen, Soren et al

Conference (2013, February 08)

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See detailKivuguto traditional fermented milk and the dairy industry in Rwanda. A review
Karenzi, Eugène ULg; Mashaku, Albert; Nshimiyimana, Alphonse M. et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2013), 17(2), 383-391

Traditional methods of fermenting milk involve the use of indigenous microorganisms, leading to the production of a variety of tastes in fermented milk products. Kivuguto is a fermented milk product ... [more ▼]

Traditional methods of fermenting milk involve the use of indigenous microorganisms, leading to the production of a variety of tastes in fermented milk products. Kivuguto is a fermented milk product, which is popular in Rwanda. Kivuguto is produced by traditional spontaneous acidification of raw milk by a microflora present both on utensils and containers used for milk preservation and in the near environment of cattle. Thus, this method does not allow the shelf stability of the product. Faced to such a situation, modern dairies now produce fermented milk and other dairy products using exotic strains. The main objectives of this paper are firstly, to provide documentation on the traditional production of kivuguto, as well as its by-products, and secondly, to describe the current situation of the dairy industry in Rwanda. [less ▲]

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See detailDecommissioned dates: chemical composition and fermentation substrate for the production of extracellular catalase by an Aspergillus phoenicis mutant
Kacem-Chaouche, N.; Dehimat, L.; Meraihi, Z. et al

in Agriculture and Biology Journal of North America (2013)

The recovery of dates downgraded as a fermentation medium for the production of extracellular catalase by Aspergillus phoenicis K30 was studied. Analysis of the chemical composition of pulp and kernel ... [more ▼]

The recovery of dates downgraded as a fermentation medium for the production of extracellular catalase by Aspergillus phoenicis K30 was studied. Analysis of the chemical composition of pulp and kernel flour of dates showed that the pulp had a considerably greater carbohydrate content compared to the kernel (84 vs 2.93% respectively). However, the kernel flour was richer in nitrogen (0.68% vs 0.34), mineral elements (3.63 vs 1.28%) and in essential fatty acids C18: 2 vs C18: 3 than the pulp flour. The soluble extract of the date flour showed that sugars solubilised at 90% consisted of sucrose, fructose and glucose. Therefore, this extract, being an important source of carbon and energy, was used in the current study as a fermentation medium (after supplementation with 20% of corn steep) for the production of extracellular catalase by A. Phoenicis K30. During the course of this fermentation, the biomass was estimated at 18.6 g / L after 72 h of culture, while the maximum concentration of extracellular catalase (47.5 U / ml) was reached at 96 h of fermentation. The mycelium obtained in pellet form is suitable for industrial exploitation of this process. [less ▲]

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See detailModelling the β-amylase activity during red sorghum malting when Bacillus subtilis is used to control mould growth
Bwanganga Tawaba, Jean-Claude ULg; Bera, François ULg; Thonart, Philippe ULg

in Journal of Cereal Science (2013), 57

Steeping in dilute alkaline (0.2% NaOH) followed by resteeping in biocontrol (starters of Bacillus subtilis S499) has been used during red sorghum malting. The effect of steeping and germination ... [more ▼]

Steeping in dilute alkaline (0.2% NaOH) followed by resteeping in biocontrol (starters of Bacillus subtilis S499) has been used during red sorghum malting. The effect of steeping and germination conditions has been described using 2 functions: a Weibull 4-parameter model combined with a General Linear Model with Logarithm Link with significant goodness. Steeping conditions (combined use of NaOH and Bacillus subtilis S499) affects the synthesis capacity of grain: when Bacillus subtilis culture used in the steeping step is diluted, lnα increases, suggesting a loss of treatment efficacy. The germination temperature affects the β-amylase synthesis rate during the induction phase: the germination temperature increase is accompanied by a decrease of the β-amylase synthesis rate. During the repression phase of β-amylase synthesis, the effect of malting conditions was found to taper. [less ▲]

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See detailHigh-energy X-ray tomography analysis of a metal packing biofilm reactor for the production of lipopeptides by Bacillus subtilis
Zune, Quentin ULg; Soyeurt, Delphine; Toye, Dominique ULg et al

in Journal of Chemical Technology & Biotechnology (2013)

BACKGROUND: Whereas multi-species biofilm reactors are commonly used for the treatment of liquid and solid wastes, new strategies are progressing for the development of single species biofilm for the ... [more ▼]

BACKGROUND: Whereas multi-species biofilm reactors are commonly used for the treatment of liquid and solid wastes, new strategies are progressing for the development of single species biofilm for the production of high-value metabolites. Technically, this new concept relies on the design of bioreactors able to promote biofilm formation and on the identification of the key physico-chemical parameters involved in biofilm formation. RESULTS: An experimental setting comprising a liquid continuously recirculated on a metal structured packing has been used to promote Bacillus subtilis GA1 biofilm formation. The colonization of the packing has been visualized non-invasively by X-ray tomography. This analysis revealed an uneven, conical, distribution of the biofilm inside the packing. Compared with a submerged culture carried out in a stirred tank reactor, significant modification of the lipopeptide profile has been observed in the biofilm reactorwith the disappearance of fengycin and iturin fractions and an increase of the surfactin fraction. In addition, considering the biofilm reactor design, no foam formation has been observed during the culture. CONCLUSIONS: The configuration of this biofilm reactor set-up allows for a higher surfactin production by comparison with a submerged culture while avoiding foam formation. Additionally, scale-up could easily be performed by increasing the number of packing elements. [less ▲]

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See detailVers une intégration du sorgho comme matière première pour la brasserie moderne (synthèse bibliographique)
Bwanganga Tawaba, J.-C.; Ba, K.; Destain, Jacqueline ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2013), 17(4), 622-633

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See detailProteomic investigation of aphid honeydew reveals an unexpected diversity of proteins
Vandermoten, Sophie ULg; Sabri, Ahmed; Leroy, Pascal et al

in PLoS ONE (2013), 8(9): e74656

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See detailOn-line profiling of Escherichia coli stress response
Brognaux, Alison ULg; Shanshan, Han; Sorensen, Soren et al

in Communications in Agricultural and Applied Biological Sciences (2013)

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See detailBiofilm formation on metal structured packing for the production of high added value biomolecules
Zune, Quentin ULg; Zune, Quentin ULg; Toye, Dominique ULg et al

in Récents Progrès en Génie des Procédés (2013)

Many white biotechnology bioprocesses apply techniques from chemical engineering based on bioreactors with mechanical stirring system commonly employed in pharmaceutical sector, food industry or energy ... [more ▼]

Many white biotechnology bioprocesses apply techniques from chemical engineering based on bioreactors with mechanical stirring system commonly employed in pharmaceutical sector, food industry or energy field (Dasilva, 2004). As in chemical engineering, scale-up of these bioprocesses induces physicochemical constraints that affect physiological pathways and decrease performances. In this context, it is essential to think new bioprocesses better suited to physiology of microorganisms, minimizing physicochemical constraints. The aim of this work consists to use stainless steel structured packing (SSP) with high specific area (500-750 m²/m³) as inert support for biomass immobilization in order to produce high added value biomolecules. These bioreactors are biocatalysts in which microbial system is immobilized biomass on the form of a biofilm performing bioconversion of a substrate into a specific product (Rosche, 2009). In this study, an experimental setting containing a SSP reproduces solid-state fermentation (SSF) like conditions. Two well known microorganisms for their ability to form biofilm and secrete metabolites are tested in the experimental setting : Bacillus subtilis for its lipopeptides and Aspergillus oryzae for its glucoamylase. Effectiveness of the bioprocess in term of dynamic of the excretion of the target biomolecule is compared with a classical submerged culture (SmF). For lipopeptides production from B. subtilis, SSP is located in a 20L bioreactor continuously aspersed by liquid medium required to the growth of the biofilm. In the case of A. oryzae, the SSP is partially immerged in a 250 mL shake flask. X-ray tomography of the SSP allows non-invasive visualization and quantification of biofilm repartition inside the support. Implementation of SSP permits almost total immobilization of biomass on the form of a mono-species biofilm to the detriment of the liquid phase. Processing of images obtained by X-ray tomography of the SSP provides relevant information for the optimization of the bioprocess. For both microorganism species, results indicate the influence of parameters such as hydrodynamics, aeration rate and microorganism specificity, on the biofilm morphology inside the support and the performances of the bioprocess. SSF-like conditions in the experimental setting lead to technologic progress, such as absence of foam formation, persistence of the microbial system, and improve the dynamic of metabolites excretion compared with conditions imposed by the submerged culture. Further experiment will consider hydrodynamics aspects and amount of carbon source on effectiveness of the bioprocess. [less ▲]

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See detailSymbiont Diversity in Reticulitermes santonensis (Isoptera: Rhinotermitidae): Investigation Strategy Through Proteomics.
Bauwens, Julien ULg; Millet, Catherine ULg; Tarayre, Cédric ULg et al

in Environmental entomology (2013), 42(5), 882-7

The complex microbial community living in the hindgut of lower termites includes prokaryotes, flagellates, yeasts, and filamentous fungi. Many microorganisms are found in the termite gut, but only a few ... [more ▼]

The complex microbial community living in the hindgut of lower termites includes prokaryotes, flagellates, yeasts, and filamentous fungi. Many microorganisms are found in the termite gut, but only a few are thought to be involved in symbiotic association to participate in cellulose digestion. Proteomics provides analyses from both taxonomical and functional perspectives. We aimed to identify symbiont diversity in the gut of Reticulitermes santonensis (Feytaud), via complementary electrospray ionization associated to ion trap tandem mass spectrometry (LC-MS/MS) and two-dimensional gel electrophoresis associated to matrix-assisted laser desorption-ionization-time-of-flight mass spectrometry analysis. One specific challenge to the study of lower termites is the relatively few data available on abundant symbiotic flagellates. Analysis based on LC-MS/MS revealed few protein families showing assignments to eukaryotes and the taxonomic origin of highly represented actins could not be established. Tubulins proved to be the most suitable protein family with which to identify flagellate populations from hindgut samples using LC-MS/MS, compared with other protein families, although this method targeted few prokaryotes in our assay. Similarly, two-dimensional gel electrophoresis associated to matrix-assisted laser desorption-ionization-time-of-flight mass spectrometry did not succeed in identifying flagellate populations, but did permit the identification of most of the prokaryotic components of the symbiotic system. Finally, fungi and yeasts were identified by both methods. Owing to the lack of sequenced genes in flagellates, targeting tubulins for LC-MS/MS could allow fingerprints of flagellate populations to be established. Experimental and technical improvements might increase the efficiency of identification of prokaryotic populations in the near future, based on metaproteomic development. [less ▲]

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See detailIn Vitro and In Vivo Characterization of Plant Growth Promoting Bacillus Strains Isolated from Extreme Environments of Eastern Algeria.
Ait-Kaki, Asma; Kacem-Chaouche, Noreddine; Ongena, Marc ULg et al

in Applied biochemistry and biotechnology (2013)

This report is to our knowledge the first to study plant growth promotion and biocontrol characteristics of Bacillus isolates from extreme environments of Eastern Algeria. Seven isolates of 14 (50 %) were ... [more ▼]

This report is to our knowledge the first to study plant growth promotion and biocontrol characteristics of Bacillus isolates from extreme environments of Eastern Algeria. Seven isolates of 14 (50 %) were screened for their ability to inhibit growth of some phytopathogenic fungi on PDA and some roots exudates. The bacteria identification based on 16S r-RNA and gyrase-A gene sequence analysis showed that 71 % of the screened isolates belonged to Bacillus amyloliquefaciens and the rest were closely related to B. atrophaeus and B. mojavensis. Most of them had high spore yields (22 x 108-27 x 108 spores/ml). They produced protease and cellulase cell wall-degrading enzymes while the chitinase activity was only observed in the B. atrophaeus (6SEL). A wide variety of lipopeptides homologous was detected by liquid chromatography-electrospray ionization-mass spectrometry analysis. Interestingly, some additional peaks with new masses were characterized, which may correspond to new fengycin classes. The isolates produced siderophores and indole-3- acetic acid phytohormone. The greenhouse experiment using a naturally infested soil with Sclerotonia sclerotiorum showed that the B. atrophaeus (6SEL) significantly increased the size of the chickpea plants and reduced the stem rot disease (P < 0.05). These results suggest that these isolates may be used further as bio-inoculants to improve crop systems. [less ▲]

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See detailVolatile compounds of the traditional sorghum beers “ikigage” brewed with Vernonia amygdalina “umubirizi”
Lyumugabe, F.; Bajyana Songa, E.; Wathelet, Jean-Paul ULg et al

in Cerevisia : Belgian Journal of Brewing and Biotechnology (2013), 37

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See detailComparative biochemical analysis during the anaerobic digestion of lignocellulosic biomass from six morphological parts of Williams Cavendish banana (Triploid Musa AAA group) plants
Kamdem, Irenee ULg; Hiligsmann, Serge ULg; Vanderghem, Caroline ULg et al

in World Journal of Microbiology & Biotechnology (2013)

We studied banana lignocellulosic biomass (BALICEBIOM) that is abandoned after fruit harvesting, and assessed its biochemical methane potential, because of its potential as an energy source. We monitored ... [more ▼]

We studied banana lignocellulosic biomass (BALICEBIOM) that is abandoned after fruit harvesting, and assessed its biochemical methane potential, because of its potential as an energy source. We monitored biogas production from six morphological parts (MPs) of the "Williams Cavendish" banana cultivar using a modified operating procedure (KOP) using KOH. Volatile fatty acid (VFA) production was measured using high performance liquid chromatography. The bulbs, leaf sheaths, petioles-midribs, leaf blades, rachis stems, and floral stalks gave total biogas production of 256, 205, 198, 126, 253, and 221 ml g-1 dry matter, respectively, and total biomethane production of 150, 141, 127, 98, 162, and 144 ml g-1, respectively. The biogas production rates and yields depended on the biochemical composition of the BALICEBIOM and the ability of anaerobic microbes to access fermentable substrates. There were no significant differences between the biogas analysis results produced using KOP and gas chromatography. Acetate was the major VFA in all the MP sample culture media. The bioconversion yields for each MP were below 50 %, showing that these substrates were not fully biodegraded after 188 days. The estimated electricity that could be produced from biogas combustion after fermenting all of the BALICEBIOM produced annually by the Cameroon Development Corporation-Del Monte plantations for 188 days is approximately 10.5 × 106 kW h (which would be worth 0.80-1.58 million euros in the current market). This bioenergy could serve the requirements of about 42,000 people in the region, although CH4 productivity could be improved. © 2013 Springer Science+Business Media Dordrecht. [less ▲]

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See detailEffect of humic substances on in vitro rooting of alder (Alnus glutinosa (L.) Gaertn) and birch (Betula pendula Roth)
Tahiri, Abdelghani ULg; Destain, Jacqueline ULg; Druart, Philippe et al

Poster (2013)

Humic substances (HS) are organic compounds resulting from the physical, chemical and microbiological transformations of organic residues. Present everywhere in the nature; they are taking part in basic ... [more ▼]

Humic substances (HS) are organic compounds resulting from the physical, chemical and microbiological transformations of organic residues. Present everywhere in the nature; they are taking part in basic functionalities in any ecosystems involving soils, sediments, water and landfills. They are heterogeneous and complex carbon macromolecules. Our study aims to compare the effect of HS from différent sources on in vitro rooting of woody plants. [less ▲]

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See detailPhysicochemical characterization of dextrins prepared with amylases from sorghum malt
Ba, Khady; Blecker, Christophe ULg; Danthine, Sabine ULg et al

in Stärke = Starch (2013)

Dextrins are partially hydrolyzed starch products which are used in a wide range of applications. Hydrolysis can be performed by acid or enzymatic reaction. However the properties of dextrins are ... [more ▼]

Dextrins are partially hydrolyzed starch products which are used in a wide range of applications. Hydrolysis can be performed by acid or enzymatic reaction. However the properties of dextrins are influenced by the type of reaction and the source of starch. The aim of the present study was to determine physicochemical properties of dextrins obtained from hydrolysis of starches (corn and wheat) and flours (wheat and cassava) by using sorghum malt amylases. Hydrolysis of starches and flours was performed at 65°C, the hydrolysates were centrifuged and spray-dried for analysis. Physicochemical and structure of the powders were investigated. Results showed that the proportion of DP2 (maltose and isomaltose) was higher in dextrins and more in dextrins from wheat flour. Low water activity and low dissolution time were found in all dextrins. XRD patterns revealed that the crystalline structure partially disappeared in some of them. At 30% concentration, we noted a Newtonian behavior for the dextrins. The freeze-concentrated T0 g and the peak melting temperature (T0 m) determined by DSC (DSC) showed lowest values for dextrins from wheat. Thermogravimetric analysis (TGA) revealed that the dextrins were quite stable until 200°C. [less ▲]

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