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1.
Food Funct ; 11(1): 1087-1097, 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31825447

RESUMO

Native rice starch was modified using different methods which included debranching (DB), octenyl succinylation (OSA), debranching followed by octenyl succinylation (DBOS) and octenyl succinylation followed by debranching (OSDB). The effect of different modifications and the impact of modified starch properties (resistant starch content (RS) and degree of substitution (DS)) on the gastrointestinal fate of emulsified lipids are elucidated using an in vitro digestion model that included the mouth, stomach, and small intestine phases in order to understand their functionality for further applications. The effect of the different modified rice starches on the particle size distribution of the lipid droplets, surface charge (ζ-potential), microstructure, lipid digestion (free fatty acid (FFA) release), and starch hydrolysis was also assessed. The OSA-modified starch and DBOS starch-based emulsions were found stable during the mouth phase and were also found to demonstrate lesser flocculation and coalescence in comparison with the other emulsions due to the presence of more OSA groups that provide greater steric hindrance and better protection from the gastrointestinal conditions. Furthermore, the DBOS starch was found to form emulsions that were more resistant to digestion with a degree of FFA release like dietary fibers and a lower extent of starch digestion that can be attributed to their higher resistant starch content (RS). Thus, the DBOS starch-based emulsions were found to be suitable for further applications such as developing functional foods to control satiety or for designing delivery systems for the sustained release of bioactive compounds.

2.
J Food Sci ; 84(11): 3213-3221, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31589344

RESUMO

Vitamin D3 was encapsulated in 10% wt soybean oil-in-water (O/W) Pickering emulsions stabilized by either nanofibrillated cellulose (NFC) or whey protein isolate (WPI) at 0.3%, 0.5%, and 0.7% w/w. The vitamin D3 -enriched emulsions were tested for their stability against temperature (30 °C to 90 °C), pH (2 to 8), and ionic strength (0 to 500 mM NaCl). The mean particle diameter (d32 ), ζ-potential, and creaming stability of the oil droplets in the emulsions were measured, as well as their vitamin D3 encapsulation efficiency (EE). After preparation, the oil droplet size (d32 ) of the emulsions stabilized by NFC increased with increasing emulsifier concentration, whereas the droplet size of emulsions stabilized by WPI decreased. NFC provided good stability to the emulsions through a combination of steric and electrostatic repulsion. The EE of vitamin D3 increased with increasing emulsifier concentration. Heating or ionic strength did not significantly (P < 0.05) affect the emulsions properties and EE. On the other hand, the NFC-stabilized emulsions were sensitive to highly acidic conditions (pH 2), with an increase in particle size and decrease in EE. The WPI-stabilized emulsions aggregated around the isoelectric point of the adsorbed proteins (pI ≈ 4.8). Increasing NFC or WPI concentration improved the stability and EE of the emulsions against environmental stresses. NFC-stabilized emulsions had good long-term stability. The results show that NFC can be used as an effective emulsifier for creating vitamin-enriched emulsions with good stability. PRACTICAL APPLICATION: This study can be used to develop more effective encapsulation technologies for fat-soluble vitamins in emulsion-based food products. Encapsulation using nanofibrillated cellulose effectively protected the encapsulated vitamins against environmental stresses which occur in industrial food production (such as pH changes, salt addition, and thermal processing). Moreover, nanofibrillated cellulose extracted from mangosteen rind is a nature-derived emulsifier that is environmental friendly.


Assuntos
Celulose/química , Colecalciferol/química , Composição de Medicamentos/métodos , Emulsões/química , Garcinia mangostana/química , Composição de Medicamentos/instrumentação , Estabilidade de Medicamentos , Emulsificantes/química , Concentração Osmolar , Tamanho da Partícula , Cloreto de Sódio/química , Eletricidade Estática , Temperatura Ambiente , Água/química
3.
Int J Biol Macromol ; 137: 666-675, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31252009

RESUMO

Flour and starch from four Thai pigmented rice cultivars, i.e., Riceberry (RB), Hom Nil (HN), Niaw Dang (ND), and Kum Pleuak Khao (KP) were compared for their physicochemical and rheological properties. Amylose content of all rice starches decreased in the following order: RB (12.09%) > HN (8.14%) > KP (2.87%) ~ ND (2.77%). The HN starch had the lowest proportion of amylopectin short A chains, while the KP starch showed the highest. Pasting temperature, setback, and final viscosity increased, while breakdown and swelling power decreased with increasing amylose content for both flour and starch samples. The flours and starches from the RB and HN showed greater onset and peak temperatures and enthalpy change (ΔH) of gelatinization than those from the ND and KP. Moreover, the gelatinization temperatures of all starches were significantly lower, but ΔH was higher than their flour counterparts. Dynamic viscoelastic tests revealed weak-gel like behavior of all flour and starch gels as evidenced by their G' > G″ and tan δ values were smaller than unity.


Assuntos
Fenômenos Químicos , Farinha/análise , Oryza/química , Reologia , Amido/química , Amilose/análise , Cor , Tamanho da Partícula , Solubilidade , Tailândia , Viscosidade
4.
Food Res Int ; 116: 559-565, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30716980

RESUMO

Hydroxypropyl methylcellulose (HPMC) was used as a co-emulsifier with chitosan and the whole cells of bacteriocin-producing Lactococcus lactis IO-1 (L. lactis IO-1) for the preparation of bacteria interface Pickering emulsion. The obtained emulsion exhibited a high stability against centrifugation force, ionic strength and low temperature, with the whole cells of L. lactis IO-1 located at the oil/water interface. Because L.lactis IO-1 was found to produce peptide lantibiotic against several strains of Gram-positive food pathogen, the highly stable emulsion demonstrated in this study exhibited high potential as an antimicrobial emulsion with several health benefits of chitosan and HPLC useful for food industry.


Assuntos
Quitosana/química , Derivados da Hipromelose/química , Lactococcus lactis/fisiologia , Óleos/química , Probióticos/química , Água/química , Bacteriocinas/metabolismo , Emulsões , Lactococcus lactis/metabolismo , Viabilidade Microbiana
5.
J Hazard Mater ; 339: 82-90, 2017 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-28628786

RESUMO

In this study, a non-pathogenic, BTEX-degrading Microbacterium esteraromaticum SBS1-7 was isolated from estuarine sediment in Thailand via an enrichment technique. M. esteraromaticum SBS1-7 was able to degrade all six BTEX components, in both liquid medium and soil slurry system, when BTEX was supplied as an individual component or a mixture. It exhibited a high level of tolerance towards a wide range of hydrocarbons and also utilized alkanes and naphthalene. Detection of metabolites produced during BTEX and naphthalene degradation revealed highly extensive biodegradation pathways used by M. esteraromaticum SBS1-7. Toluene was metabolized via activities of both monooxygenase (toluene 4-monooxygenase or T4MO) and dioxygenases (toluene dioxygenase or TDO and naphthalene 1,2-dioxygenase or NDO). Benzene was metabolized via phenol, possibly by an activity of T4MO. Ethylbenzene was converted into styrene and 1-phenethyl alcohol by a well-documented activity of NDO. Dioxidation of ethylbenzene, possibly by ethylbenzene dioxygenase or EBDO, was also found. All xylene isomers were converted into their corresponding alcohols via an activity of NDO while naphthalene was metabolized via dioxidation reaction by the same enzyme. This study is, by far, the first direct evidence of BTEX biodegradation by a non-pathogenic, rhizosphere bacterium M. esteraromaticum.


Assuntos
Actinobacteria/metabolismo , Derivados de Benzeno/metabolismo , Benzeno/metabolismo , Poluentes Ambientais/metabolismo , Tolueno/metabolismo , Xilenos/metabolismo , Actinobacteria/isolamento & purificação , Biodegradação Ambiental , Estuários , Sedimentos Geológicos/microbiologia
6.
Food Res Int ; 78: 79-87, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28433320

RESUMO

The influence of starch type (resistant starch (RS) versus native (NS) starch) and concentration (10 and 35wt.%) on the potential gastrointestinal fate of digestible lipid (corn oil) droplets encapsulated within starch hydrogels was studied using a simulated gastrointestinal tract (GIT). The NS used was a normal corn starch, whereas the RS used was a high amylose corn starch. Changes in morphology, organization, size, and charge of the particles in the delivery systems were measured as they passed through each stage of the GIT model: mouth, stomach, and small intestine. The GIT fates of three types of delivery system were compared: free lipid droplets; lipid droplets in RS-hydrogels; and, lipid droplets in NS-hydrogels. Encapsulation of the lipid droplets in the hydrogels had a pronounced influence on their GIT behavior, with the effect depending strongly on starch type. The starch granules in the RS-hydrogels remained intact throughout the simulated GIT because their compact structure makes them resistant to enzyme digestion. The initial rate of lipid digestion in the small intestine phase also depended on delivery system type: emulsion>RS-hydrogels>NS-hydrogels. However, the lipid phase appeared to be fully digested at the end of the digestion period for all samples. These results provide useful information for designing functional foods for improved health. For example, food matrices could be developed that slowdown the rate of lipid digestion, and therefore prevent a spike in serum triacylglycerols in the blood, which may be advantageous for developing functional foods to tackle diabetes.

7.
Bioprocess Biosyst Eng ; 38(4): 701-9, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25341365

RESUMO

The use of bacterial cell or biocatalyst for industrial synthetic chemistry is on the way of significant growth since the biocatalyst requires low energy input compared to the chemical synthesis and can be considered as a green technology. However, majority of natural bacterial cell surface is hydrophilic which allows poor access to the hydrophobic substrate or product. In this study, Escherichia coli (E. coli) as a representative of hydrophilic bacterial cells were accumulated at the oil-water interface after association with chitosan at a concentration range of 0.75-750 mg/L. After association with negatively charged E coli having a ζ potential of -19.9 mV, a neutralization of positively charged chitosan occurred as evidenced by an increase in the ζ potential value of the mixtures with increasing chitosan concentration up to +3.5 mV at 750 mg/L chitosan. Both emulsification index and droplet size analysis revealed that chitosan-E. coli system is an excellent emulsion stabilizer to date because the threshold concentration was as low as 7.5 mg/L or 0.00075% w/v. A dramatic increase in the surface hydrophobicity of the E. coli as evidenced by an increase in contact angle from 19 to 88° with increasing chitosan concentration from 0 to 750 mg/L, respectively, resulted in an increase in the stability of oil-in-water emulsions stabilized by chitosan-E. coli system. The emulsion was highly stable even the emulsification was performed under 20% salt condition, or temperature ranged between 20 and 50 °C. Emulsification was failed when the oil volume fraction was higher than 0.5, indicating that no phase inversion occurred. The basic investigation presented in this study is a crucial platform for its application in biocatalyst industry and bioremediation of oil spill.


Assuntos
Quitosana/química , Microbiologia Industrial , Água/química , Catálise , Relação Dose-Resposta a Droga , Emulsões/química , Escherichia coli/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Íons , Microscopia Eletrônica de Varredura , Tamanho da Partícula , Propriedades de Superfície , Temperatura Ambiente
8.
J Colloid Interface Sci ; 426: 333-40, 2014 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-24863801

RESUMO

The impact of biological surfactants (bile salts) on the protein (ß-lactoglobulin) corona surrounding gold nanoparticles (200 nm) was studied using a variety of analytical techniques at pH 7: dynamic light scattering (DLS); particle electrophoresis (ζ-potential); UV-visible (UV) spectroscopy; transmission electron microscopy (TEM); and surface-enhanced Raman scattering (SERS). The bile salts adsorbed to the protein-coated nanoparticle surfaces and altered their interfacial composition, charge, and structure. SERS spectra of protein-coated nanoparticles after bile salt addition contained bands from both protein and bile salts, indicating that the protein was not fully displaced by the bile salts. UV, DLS and TEM techniques also indicated that the protein coating was not fully displaced from the nanoparticle surfaces. The impact of bile salts could be described by an orogenic mechanism: mixed interfaces were formed that consisted of islands of aggregated proteins surrounded by a sea of bile salts. This knowledge is useful for understanding the interactions of bile salts with protein-coated colloidal particles, which may be important for controlling the fate of colloidal delivery systems in the human gastrointestinal tract, or the gastrointestinal fate of ingested inorganic nanoparticles.


Assuntos
Ácidos e Sais Biliares/química , Ouro/química , Lactoglobulinas/química , Nanopartículas Metálicas , Nanopartículas , Proteínas/química , Tensoativos/química , Espectrofotometria Ultravioleta
9.
Carbohydr Polym ; 107: 182-91, 2014 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-24702934

RESUMO

Seven types of starch (waxy corn, normal corn, waxy rice, normal rice, waxy potato, normal potato, and tapioca) were selected to produce slowly digestible maltodextrins by enzymatic modification using a previously developed procedure. Branching enzyme (BE) alone and in combination with ß-amylase (BA) were used to increase the amount of α-1,6 branching points, which are slowly hydrolyzed by mucosal α-glucosidases in the small intestine. The enzymatic treatments of all starches resulted in a reduction of the debranched linear chain length distribution and weight-average molecular weight. After α-amylolysis of the enzymatically synthesized-maltodextrins, the proportion of branched α-limit dextrins increased, and consequently a reduction in rate of glucose release by rat intestinal α-glucosidases in vitro. Among the samples, enzyme-modified waxy starches had a more pronounced effect on an increase in the slow digestion property than normal starches. These enzyme-modified maltodextrins show potential as novel functional foods by slowing digestion rate to attain extended glucose release.


Assuntos
Glucose/metabolismo , Polissacarídeos/biossíntese , Polissacarídeos/química , Amido/metabolismo , beta-Amilase/metabolismo , Animais , Glucose/química , Cinética , Peso Molecular , Polissacarídeos/metabolismo , Ratos , Rhodothermus/enzimologia , Amido/química
10.
Carbohydr Polym ; 102: 790-8, 2014 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-24507348

RESUMO

Non-chemical modification of tapioca starch was investigated using jet atmospheric argon plasma treatment. Two forms of starch slurry, i.e. granular starch (G) and cooked starch (C), were jet-treated by argon plasma generated by supplying input power of 50 W (denoted as G50 and C50 samples) and 100 W (denoted as G100 and C100 samples) for 5 min. Physical, rheological, and structural characteristics of the modified starch were investigated. The G50 and C100 samples had lower paste clarity but higher thermal stability and performed stronger gels (G50 only) compared to their control counterparts. On the other hand, the analyzed properties of the G100 and C50 samples showed the opposite trend. FTIR and (1)H NMR results revealed that the relative areas of COC and OH peaks were changed after the treatment. Cross-linking reaction seemed to predominantly take place for the G50 and C100 samples, whereas depolymerization predominated for the G100 and C50 samples.

11.
J Colloid Interface Sci ; 416: 184-9, 2014 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-24370420

RESUMO

In this work, we investigated the conformational changes of a globular protein (ß-lactoglobulin, ß-lg) coated on the surface of 200 nm gold nanoparticles (GNPs) using a number of analytical techniques: dynamic light scattering (DLS); particle electrophoresis (ζ-potential); localized surface plasmon resonance (LSPR) spectroscopy; transmission electron microscopy (TEM); and surface-enhanced Raman scattering (SERS). The ß-lg (pH 3) concentration had a pronounced effect on the aggregation and surface charge of ß-lg-coated GNPs. The surface charge of GNPs changed from negative to positive as increasing amounts of ß-lg molecule were added, indicating that the globular protein molecules adsorbed to the surfaces of the particles. Extensive particle aggregation occurred when ß-lg did not saturate the GNP surfaces, which was attributed to electrostatic bridging flocculation. Modifications in LSPR and SERS spectra after addition of ß-lg to the GNP suspensions supported the adsorption of ß-lg to the particle surfaces. Moreover, SERS highlighted the importance of a number of specific molecular groups in the binding interaction, and suggested conformational changes of the globular protein after adsorption. This research provides useful information for characterizing and understanding the interactions between globular proteins and colloidal particles.


Assuntos
Ouro/química , Lactoglobulinas/química , Nanopartículas Metálicas/química , Água/química , Adsorção , Animais , Bovinos , Floculação , Concentração de Íons de Hidrogênio , Luz , Nanopartículas Metálicas/ultraestrutura , Tamanho da Partícula , Conformação Proteica , Espalhamento de Radiação , Análise Espectral Raman , Ressonância de Plasmônio de Superfície , Temperatura Ambiente
12.
Carbohydr Polym ; 101: 656-65, 2014 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-24299823

RESUMO

Physicochemical properties of cross-linked tapioca starch (CLTS) with different cross-linking levels and their application as a thickening agent in soups were studied. The CLTS was prepared by cross-linking native tapioca starch suspended in alkaline solution (41.67% (w/w), pH 11) using a mixture (99:1 (w/w) ratio) of sodium trimetaphosphate (STMP) and sodium tripolyphosphate (STPP) at different concentrations ranged from 0.25% to 6.0% (w/w of starch) at 45°C for 3h. Starch paste clarity decreased with increasing concentration of STMP/STPP mixture. Variations of swelling power, solubility, pasting, gelatinization, and rheological properties of the CLTS were found. Thermogravimetric analysis exhibited higher thermal stability for the CLTS granules compared to the native one. Among the samples, the CLTS prepared using 1.0% STMP/STPP (1.0%-CLTS) and soup containing the 1.0%-CLTS exhibited the strongest gel characteristic and the greatest shear resistant properties. The 1.0%-CLTS improved the textural properties and sensory quality of soups.


Assuntos
Fenômenos Químicos , Alimentos , Manihot/química , Amido/química , Fósforo/química , Reologia , Solubilidade , Paladar
13.
Braz. j. microbiol ; 43(3): 1192-1205, July-Sept. 2012. ilus, graf, tab
Artigo em Inglês | LILACS | ID: lil-656690

RESUMO

Baffled shake flask cultivation of Aurantiochytrium sp. B-072 was carried out at in a glucose-monosodium glutamate mineral medium at different C/N-ratios (30-165) with glucose fixed at 90 g/L. With increasing C/N-ratio, a modest increase in lipid content (60 to 73 % w/w) was observed whereas fat-free biomass decreased but overall biomass showed little variation. FA-profiles were not affected to a large extent by C/N-ratio and absolute docosahexaenoic (DHA)-levels fell in narrow range (5-6 g/L). However at C/N > 64 a rapid decrease in lipid synthetic rate and/or incomplete glucose utilization occurred. Glucose and FA-fluxes based on fat-free biomass peaked at a C/N ratio of 56. This condition was chosen for calculation of the redox balance (NAD(P)H) and energy (ATP) requirement and to estimate the in vivo P/O ratio during the main period of fatty acid biosynthesis. Several models with different routes for NADPH, acetyl-CoA formation and re-oxidation of OAA formed via ATP-citrate lyase were considered as these influence the redox- and energy balance. As an example, using a commonly shown scheme whereby NADPH is supplied by a cytosolic "transhydrogenase cycle" (pyruvate-OAA-malate-pyruvate) and OAA formed by ATP-citrate lyase is recycled via import into the mitochondria as malate, the calculated NADPH-requirement amounted to 5.5 with an ATP-demand of 10.5 mmol/(g fat-free biomass x h) and an in vivo P/O-ratio (not including non-growth associated maintenance) of 1.6. The lowest ATP requirement is found when acetyl-CoA would be transported directly from the mitochondria to the cytosol by carnitine acetyltransferase. Assay of some enzymes critical for NADPH supply indicates that activity of glucose-6-phosphate dehydrogenase, the first enzyme in the HMP pathway, is far insufficient for the required NADPH-flux and malic enzyme must be a major source. Activity of the latter (ca. 300 mU/mg protein) far exceeds that in oleaginous fungi and yeast.


Assuntos
Ácidos Graxos/análise , Biomassa , Ácidos Docosa-Hexaenoicos , Eucariotos/enzimologia , Glucose/biossíntese , Lipídeos/análise , Oxidação/análise , Ativação Enzimática , Métodos
14.
Langmuir ; 28(13): 5729-36, 2012 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-22443382

RESUMO

An oil-in-water Pickering emulsion stabilized by biobased material based on a bacteria-chitosan network (BCN) was developed for the first time in this study. The formation of self-assembled BCN was possible due to the electrostatic interaction between negatively charged bacterial cells and polycationic chitosan. The BCN was proven to stabilize the tetradecane/water interface, promoting formation of highly stable oil-in-water emulsion (o/w emulsion). We characterized and visualized the BCN stabilized o/w emulsions by scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). Due to the sustainability and low environmental impact of chitosan, the BCN-based emulsions open up opportunities for the development of an environmental friendly new interface material as well as the novel type of microreactor utilizing bacterial cells network.


Assuntos
Bactérias/metabolismo , Quitosana/metabolismo , Bactérias/química , Bactérias/citologia , Tampões (Química) , Sobrevivência Celular , Quitosana/química , Emulsões , Concentração de Íons de Hidrogênio , Óleos/química , Solventes/química , Eletricidade Estática , Água/química
15.
Braz J Microbiol ; 43(3): 1192-205, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24031944

RESUMO

Baffled shake flask cultivation of Aurantiochytrium sp. B-072 was carried out at in a glucose-monosodium glutamate mineral medium at different C/N-ratios (30-165) with glucose fixed at 90 g/L. With increasing C/N-ratio, a modest increase in lipid content (60 to 73 % w/w) was observed whereas fat-free biomass decreased but overall biomass showed little variation. FA-profiles were not affected to a large extent by C/N-ratio and absolute docosahexaenoic (DHA)-levels fell in narrow range (5-6 g/L). However at C/N > 64 a rapid decrease in lipid synthetic rate and/or incomplete glucose utilization occurred. Glucose and FA-fluxes based on fat-free biomass peaked at a C/N ratio of 56. This condition was chosen for calculation of the redox balance (NAD(P)H) and energy (ATP) requirement and to estimate the in vivo P/O ratio during the main period of fatty acid biosynthesis. Several models with different routes for NADPH, acetyl-CoA formation and re-oxidation of OAA formed via ATP-citrate lyase were considered as these influence the redox- and energy balance. As an example, using a commonly shown scheme whereby NADPH is supplied by a cytosolic "transhydrogenase cycle" (pyruvate-OAA-malate-pyruvate) and OAA formed by ATP-citrate lyase is recycled via import into the mitochondria as malate, the calculated NADPH-requirement amounted to 5.5 with an ATP-demand of 10.5 mmol/(g fat-free biomass x h) and an in vivo P/O-ratio (not including non-growth associated maintenance) of 1.6. The lowest ATP requirement is found when acetyl-CoA would be transported directly from the mitochondria to the cytosol by carnitine acetyltransferase. Assay of some enzymes critical for NADPH supply indicates that activity of glucose-6-phosphate dehydrogenase, the first enzyme in the HMP pathway, is far insufficient for the required NADPH-flux and malic enzyme must be a major source. Activity of the latter (ca. 300 mU/mg protein) far exceeds that in oleaginous fungi and yeast.

16.
Bioresour Technol ; 98(2): 281-7, 2007 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16563749

RESUMO

The effect of coconut water (CW) on biomass and docosahexaenoic acid (DHA, C22:6 n3) formation by Schizochytrium mangrovei Sk-02 was studied in a yeast extract-diluted sea water medium. Optimal CW-level was ca. 33% (v/v), resulting in a biomass level of 28 g/l with a DHA-content of 20% (w/w) or 6 g DHA/l, almost 50% higher than in non-supplemented cultures at the same initial sugar level. Study on the growth-promoting effects of coconut water suggested that it could be (partially) mimicked by addition of trace elements; the fatty acids present in CW did not appear to be incorporated or effect fatty acid formation by the organism. CW-addition was also effective in media with other nitrogen sources such as casitone, peptone and tryptone. Its inclusion (at 50% v/v) increased biomass levels two-to-three-fold with concomitant increases in the DHA-level.


Assuntos
Cocos/química , Ácidos Docosa-Hexaenoicos/metabolismo , Eucariotos/metabolismo , Água/química , Animais , Reatores Biológicos , Meios de Cultura
17.
J Hazard Mater ; 137(3): 1643-8, 2006 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-16849032

RESUMO

This study examines hydrothermal decomposition of Baker's yeast cells, used as a model for spent Brewer's yeast waste, into protein and amino acids. The reaction was carried out in a closed batch reactor at various temperatures between 100 and 250 degrees C. The reaction products were separated into water-soluble and solid residue. The results demonstrated that the amount of yeast residue decreased with increasing hydrolysis temperature. After 20 min reaction in water at 250 degrees C, 78% of yeast was decomposed. The highest amount of protein produced was also obtained at this condition and was found to be 0.16 mg/mg dry yeast. The highest amount of amino acids (0.063 mg/mg dry yeast) was found at the lowest temperature tested after 15 min. The hydrolysis product obtained at 200 degrees C was tested as a nutrient source for yeast growth. The growth of yeast cells in the culture medium containing 2 w/v% of this product was comparable to that of the cells grown in the medium containing commercial yeast extract at the same concentration. These results demonstrated the feasibility of using subcritical water to potentially decompose proteinaceous waste such as spent Brewer's yeast while recovering more useful products.


Assuntos
Aminoácidos/biossíntese , Proteínas de Saccharomyces cerevisiae/biossíntese , Saccharomyces cerevisiae/metabolismo , Água/metabolismo , Resíduos Industriais , Cinética , Solubilidade , Temperatura Ambiente
18.
Bioresour Technol ; 96(17): 1851-9, 2005 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16084365

RESUMO

This study concerns the production of yeast extract from spent brewer's yeast using rotary microfiltration as a means to combine debittering and cell debris separation into a single step, without using a toxic alkali wash. The pH of yeast homogenate was found to affect protein yield and bitterness of the product. Rotary filtration of yeast homogenate at various pHs resulted in different percent protein transmissions. These were found to be 5.05%, 9.83%, and 30.83% for pH 5, 6, and 7.5, respectively. The bitterness concentration in the permeate was also found to be higher at higher pHs. Autolysis of the cell homogenate prior to filtration increased protein yield and decreased bitterness considerably. At pH 5.5, the protein transmission was increased to 60% and debittering efficiency was increased from 59% to 86%. The permeate flux and protein productivity could be further increased by increasing the rotational speed, but this resulted in a decrease in debittering efficiency. Thus, the rotational speed should be carefully selected to compromise between the yield and product quality. Furthermore, for the tested rotational speeds of 600 and 1000 rpm, the change in feed flow rate from 11 to 35 L h(-1) changes the flow behavior from turbulent vortex flow to laminar vortex flow, thus decreasing the flux and protein productivity.


Assuntos
Saccharomyces cerevisiae , Ultrafiltração/métodos , Concentração de Íons de Hidrogênio , Permeabilidade , Pressão , Rotação , Paladar , Fatores de Tempo
19.
J Econ Entomol ; 96(2): 292-9, 2003 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-14994793

RESUMO

Bacillus thuringiensis is the most widely used biopesticide among many methods available to control insects. To make a saleable product, B. thuringiensis must be substantially concentrated by removal of water and formulated to improve longevity, efficacy, and ease of transport of the product. B. thuringiensis subsp. aizawai culture broth as an active ingredient was mixed with various adjuvants and then spray dried. The optimum conditions for spray drying were found to be an outlet temperature of 60-85 degrees C and an inlet temperature of 120-180 degrees C. Various adjuvants had different effects on physical and biological properties of the dried product. Gelatinized tapioca starch and milk powder improved suspensibility but adversely affected wettability of the dried formulated product. Vegetable oil and Tween 20 enhanced wettability but resulted in poor suspensibility. Silica fume was used to enhance flowability because it reduced clumping and caking of the powder resulting from the addition of vegetable oil. Formulation containing 10% wt:wt B. thuringiensis, 10% wt:wt gelatinized tapioca starch, 10% wt:wt sucrose, 38% wt:wt tapioca starch, 20% wt:wt milk powder, 10% wt:wt silica fume, 2% wt:wt polyvinyl alcohol, 5% vol:vol Tween 20, 1% vol:vol refined rice bran oil, and 1% vol:vol antifoam solution was found to be optimum in terms of the physical and biological properties of the dried product. This formulation had 55% suspensibility, 24 s for wetting time, and 5.69 x 10(4) CFU/ml of LC50 value against Spodoptera exigua larvae.


Assuntos
Bacillus thuringiensis , Controle Biológico de Vetores/métodos , Agroquímicos/administração & dosagem , Agroquímicos/análise , Fenômenos Químicos , Química Física , Microscopia Eletrônica de Varredura , Pós
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