RESUMEN
BACKGROUND: Citrus pre-harvest fruit drop, caused by huanglongbing infection, has increased dramatically concomitant with declining tree health and crop harvest size. This loss of harvestable fruit is damaging to both growers and juice processors. Recovering and converting this fruit to alternative value added products would benefit the citrus industry. Therefore, we have explored the potential of using this fruit as a feedstock in our newly developed pilot scale continuous steam explosion process. RESULTS: Whole fruits were converted to steam-exploded biomass using a continuous pilot scale process. The sugar composition of raw fruit and steam-exploded biomass was determined. Recovered pectic hydrocolloids and phenolic compounds were characterized. Pectic hydrocolloids comprised 78 g kg-1 of the dry material in the dropped fruit. Following the steam explosion process almost all of the pectic hydrocolloids were recoverable with a water wash. They could be functionalized in situ or separated from the milieu. Additionally, approximately 40% of the polymethoxylated flavones, 10% of the flavanone glycosides, 85% of the limonoids and almost 100% of hydroxycinnamates were simultaneously recovered. CONCLUSION: The continuous steam explosion of pre-harvest dropped citrus fruit provides an enhanced, environmentally friendly method for the release and recovery of valuable coproducts from wasted biomass. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.
Asunto(s)
Citrus/química , Pectinas/química , Fenoles/química , Citrus/crecimiento & desarrollo , Citrus/microbiología , Coloides/análisis , Manipulación de Alimentos , Frutas/química , Frutas/crecimiento & desarrollo , Frutas/microbiología , Pectinas/aislamiento & purificación , Fenoles/aislamiento & purificación , Enfermedades de las Plantas/microbiologíaRESUMEN
Shiga toxin (Stx)-producing, food-contaminating Escherichia coli (STEC) is a major health concern. Plant-derived pectin and pectic-oligosaccharides (POS) have been considered as prebiotics and for the protection of humans from Stx. Of five structurally different citrus pectic samples, POS1, POS2 and modified citrus pectin 1 (MCP1) were bifidogenic with similar fermentabilities in human faecal cultures and arabinose-rich POS2 had the greatest prebiotic potential. Pectic oligosaccharides also enhanced lactobacilli growth during mixed batch faecal fermentation. We demonstrated that all pectic substrates were anti-adhesive for E. coli O157:H7 binding to human HT29 cells. Lower molecular weight and deesterification enhanced the anti-adhesive activity. We showed that all pectic samples reduced Stx2 cytotoxicity in HT29 cells, as measured by the reduction of human rRNA depurination detected by our novel TaqMan-based RT-qPCR assay, with POS1 performing the best. POS1 competes with Stx2 binding to the Gb3 receptor based on ELISA results, underlining the POS anti-STEC properties.
Asunto(s)
Adhesión Bacteriana , Infecciones por Escherichia coli/microbiología , Escherichia coli O157/fisiología , Oligosacáridos/química , Pectinas/metabolismo , Prebióticos/análisis , Toxina Shiga/toxicidad , Escherichia coli O157/genética , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Heces/microbiología , Células HT29 , Humanos , Oligosacáridos/metabolismo , Pectinas/química , Toxina Shiga/metabolismoRESUMEN
Pectins extracted from a variety of sources and modified with heat and/or pH have previously been shown to exhibit activity towards several cancer cell lines. However, the structural basis for the anti-cancer activity of modified pectin requires clarification. Sugar beet and citrus pectin extracts have been compared. Pectin extracted from sugar beet pulp only weakly affected the viability of colon cancer cells. Alkali treatment increased the anti-cancer effect of sugar beet pectin via an induction of apoptosis. Alkali treatment decreased the degree of esterification (DE) and increased the ratio of rhamnogalacturonan I (RGI) to homogalacturonan. Low DE per se did not play a significant role in the anti-cancer activity. However, the enzymatic removal of galactose and, to a lesser extent, arabinose from the pectin decreased the effect on cancer cells indicating that the neutral sugar-containing RGI regions are important for pectin bioactivity.
Asunto(s)
Antineoplásicos/química , Apoptosis , Beta vulgaris/química , Pectinas/química , Extractos Vegetales/química , Antineoplásicos/farmacología , Células HT29 , Humanos , Pectinas/farmacología , Extractos Vegetales/farmacologíaRESUMEN
Pectin modified with pH, heat or enzymes, has previously been shown to exhibit anti-cancer activity. However, the structural requirements for modified pectin bioactivity have rarely been addressed. In this study several pectin extracts representing different structural components of pectin were assessed for effects against colon cancer cells. Rhamnogalacturonan I (RGI) extracts reduced proliferation of DLD1 and HCT116 colon cancer cells in a dose- and time-dependent manner. RGI reduced ICAM1 gene expression and siRNA-mediated knockdown of ICAM1 expression decreased cell proliferation providing a potential novel mechanism for the anti-cancer activity of pectin. Structural analysis of bioactive and non-bioactive RGIs suggested that a homogalacturonan component is maybe essential for the anti-proliferative activity, furthering the understanding of the structural requirements for pectin bioactivity.
Asunto(s)
Molécula 1 de Adhesión Intercelular/metabolismo , Pectinas/química , Antineoplásicos/química , Antineoplásicos/toxicidad , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Neoplasias del Colon/metabolismo , Neoplasias del Colon/patología , Células HCT116 , Humanos , Molécula 1 de Adhesión Intercelular/química , Molécula 1 de Adhesión Intercelular/genética , Espectroscopía de Resonancia Magnética , Pectinas/toxicidad , Interferencia de ARN , ARN Interferente Pequeño/metabolismoRESUMEN
Cranberry juice has been recognized as a treatment for urinary tract infections on the basis of scientific reports of proanthocyanidin anti-adhesion activity against Escherichia coli as well as from folklore. Xyloglucan oligosaccharides were detected in cranberry juice and the residue remaining following commercial juice extraction that included pectinase maceration of the pulp. A novel xyloglucan was detected through tandem mass spectrometry analysis of an ion at m/z 1055 that was determined to be a branched, three hexose, four pentose oligosaccharide consistent with an arabino-xyloglucan structure. Two-dimensional nuclear magnetic resonance spectroscopy analysis provided through-bond correlations for the α-L-Araf (1â2) α-D-Xylp (1â6) ß-D-Glcp sequence, proving the S-type cranberry xyloglucan structure. Cranberry xyloglucan-rich fractions inhibited the adhesion of E. coli CFT073 and UTI89 strains to T24 human bladder epithelial cells and that of E. coli O157:H7 to HT29 human colonic epithelial cells. SSGG xyloglucan oligosaccharides represent a new cranberry bioactive component with E. coli anti-adhesion activity and high affinity for type 1 fimbriae.
Asunto(s)
Adhesión Bacteriana/efectos de los fármacos , Bebidas/análisis , Células Epiteliales/microbiología , Escherichia coli/efectos de los fármacos , Glucanos/farmacología , Extractos Vegetales/farmacología , Vaccinium macrocarpon/química , Xilanos/farmacología , Línea Celular , Escherichia coli/fisiología , Glucanos/química , Humanos , Extractos Vegetales/química , Xilanos/químicaRESUMEN
Molecular interactions between ß-lactoglobulin (ß-LG) and sugar beet pectin (SBP) were studied using online multi-detection high performance size exclusion chromatography (HPSEC) at neutral pH and 50mM ionic strength. The hydrodynamic properties of various interacting polymer fractions were characterized in detail and compared with those of ß-LG and SBP. Results showed that â¼6.5% (w/w) of native dimeric ß-LG molecules formed complexes with over 35% SBP molecules of varying sizes, 800, 110 and 75 kDa. Although the ß-LG molecules bind to SBP molecules of all sizes and shapes, they tend to favor the intermediate (110 kDa) and small sized (75 kDa) SBP molecules. All resulting complexes possess altered shapes and hydrodynamic properties when compared to unbound SBP and ß-LG. About half of the interacting ß-LG (â¼3.5%) molecules were thought to bind to a small amount of non-covalently bound feruloyl groups, possibly present in SBP. When pre-heat treated ß-LG and SBP were combined, more than 16% of ß-LG formed complexes with at least 45% of SBP molecules of varying sizes, Mwâ¼750-800, 110, and 55-80 kDa. The complexes formed between ß-LG aggregates and/or oligomers and the large SBP molecules (750-800 kDa) adopt the shape of ß-LG aggregates, random coil. Both groups of complexes formed between ß-LG intermediate (110 kDa) and small sized (55-80 kDa) SBP take on the shape of rigid rod. It was speculated that half of the interacting heat-treated ß-LG molecules (â¼8%) are complexed with non-covalently bound feruloyl groups in SBP.
Asunto(s)
Beta vulgaris/química , Cromatografía en Gel , Lactoglobulinas/metabolismo , Pectinas/metabolismo , Calor , Hidrodinámica , Concentración de Iones de Hidrógeno , Lactoglobulinas/química , Peso Molecular , Concentración Osmolar , Pectinas/química , Unión ProteicaRESUMEN
We have solubilized and separated polysaccharides from sugar beet pulp (SBP) into three fractions with steam assisted flash extraction (SAFE). For pectin, recovery ranged from 8 to 14%, degree of methy-esterification 66-73%, crude protein 1.3-1.7%, M(w) 262-318 kDa, η(w) 0.22-0.23 dL/g, Rg(z) 36-39 nm and Rh(z) 41-42 nm. For alkaline soluble polysaccharides, (ASP I) recovery ranged from 4.0 to 6.5%, crude protein 1.2-4.8%, weight average molar mass (M(w)) 66-68 kDa, weight average intrinsic viscosity (η(w)) 0.27-0.30 dL/g, z-average radius of gyration (Rg(z)) 25-29 nm and z-average hydrated radius (Rh(z)) 10-11 nm. ASP II recovery ranged from 2.0 to 8.6%, crude protein 1.2-4.8%, M(w) 299-339 kDa, η(w) 0.22-0.33 dL/g, Rg(z) 33-34 nm and Rh(z) 30-34 nm. Recovery of the residue mainly cellulose, ranged from 20.3 to 22.3%. The cellulose in this fraction was converted to carboxymethyl cellulose (CMC). The CMC fraction contained 0.33-0.43 crude protein and had an M(w) ranging from 127 to 263 kDa, η(w) 3.6-8.0 dL/g, Rg(z) 35-45 nm and Rh(z) 27-40 nm.
Asunto(s)
Beta vulgaris/química , Fenómenos Químicos , Proteínas de Plantas/química , Polisacáridos/química , Polisacáridos/aislamiento & purificación , Carboximetilcelulosa de Sodio/química , Pectinas/química , SolubilidadRESUMEN
UNLABELLED: To improve extraction yield of pumpkin pectin, microwave heating was adopted in this study. Using hot acid extraction, pumpkin pectin yield decreased from 5.7% to 1.0% as pH increased from pH 1.0 to 2.0. At pH 2.5, no pectin was recovered from pumpkin flesh powder. After a pretreatment at pH 1.0 and 25 °C for 1 h, pumpkin powder was microwave-extracted at 120 °C for 3 min resulting in 10.5% of pectin yield. However, premicrowave treatment at 60 °C for 20 min did not improve extraction yield. When microwave heating at 80 °C for 10 min was applied after premicrowave treatment, final pectin yield increased to 11.3%. When pH was adjusted to 2.0, the yield dropped to 7.7% under the same extraction conditions. Molecular shape and properties as well as chemical composition of pumpkin pectin were significantly affected depending on extraction methods. Galacturonic acid content (51% to 58%) of pumpkin pectin was lower than that detected in commercial acid-extracted citrus pectin, while higher content of neutral sugars and acetyl esters existed in pumpkin pectin structure. Molecular weight (M(w) ) and intrinsic viscosity (η(w) ) determined for microwave-extracted pumpkin pectins were substantially lower than acid-extracted pectin, whereas polydispersity was greater. However, microwave-extracted pectin at pH 2.0 had more than 5 times greater M(w) than did the pectin extracted at pH 1.0. The η(w) of microwave-extracted pectin produced at pH 2.0 was almost twice that of other microwave-extracted pectins, which were comparable to that of acid-extracted pectin. These results indicate that extraction yield of pumpkin pectin would be improved by microwave extraction and different pectin structure and properties can be obtained compared to acid extraction. PRACTICAL APPLICATION: Pumpkin is a promising alternative source for pectin material. Pumpkin pectin has a unique chemical structure and physical properties, presumably providing different functional properties compared to conventional commercial pectin sources. Depending on the conditions to produce pumpkin pectin, diverse molecular structures can be obtained and utilized in various food applications.
Asunto(s)
Cucurbita/química , Manipulación de Alimentos/métodos , Microondas , Pectinas/química , Pectinas/aislamiento & purificación , Carbohidratos/análisis , Cromatografía de Gases y Espectrometría de Masas , Ácidos Hexurónicos/análisis , Calor , Concentración de Iones de Hidrógeno , Estructura Molecular , Peso Molecular , ViscosidadRESUMEN
The global structure of microwave-assisted flash-extracted pectins isolated from fresh sugar beet pulp has been studied. The objective was to minimize the disassembly and possibly the degradation of pectin molecules during extraction. These pectins have been characterized by high-performance size exclusion chromatography with light scattering, viscometric detection, and atomic force microscopy (AFM). Analysis of molecular parameters was performed on 15 and 8 microm size column packings. Samples analyzed with 15 microm packing gave weight-average molar masses that ranged from 532,000 to 1.2 million Da, radii of gyration from about 35 to 51 nm, polydispersities from 1.78 to 2.58, intrinsic viscosities from about 3.00 to 4.30 dL/g, and recoveries from 8.40 to 14.81% of dry weight. Chromatography revealed that a bimodal distribution of high molar mass spherical particles and lower molar mass coils was obtained. AFM images of pectin corroborated this conclusion and further revealed that these strands and spherical particles were integrated into networks. It is demonstrated that microwave-assisted extraction of sugar beet pulp under moderate pressure and at relatively low temperature could extract under acid conditions high molar mass, moderate-viscosity pectin in minutes rather than hours as required by conventional heating.
Asunto(s)
Beta vulgaris/química , Microondas , Pectinas/química , Pectinas/aislamiento & purificación , Dispersión de Radiación , Cromatografía Líquida de Alta Presión/métodos , Microscopía de Fuerza Atómica/métodos , Tamaño de la Partícula , Presión , ViscosidadRESUMEN
Images of high methoxyl orange pectin deposited from solution and high methoxyl sugar acid gels (HMSAG) were obtained by atomic force microscopy (AFM) in the tapping mode. For the first time, images of pectin deposited from water revealed that the transition from pectin networks to individual molecules or aggregates thereof occurred at concentrations between 6.5 and 13.1 microg/mL. At 6.5 microg/mL, shapes included rods, segmented rods, kinked rods, rings, branched molecules, and dense circular areas. At 13.1 microg/mL, all of these shapes were integrated into networks. These same structures were discernible in pectin high methoxyl sugar acid gels. Thus one might consider pectin networks in water at concentrations in excess of 10 microg/mL to be separate fluid precursors of networks in high methoxyl sugar acid gels. Examination of AFM images revealed that gels with "uniform" distribution of strands and pores between strands had higher gel strengths as measured by a penetrometer than gels in which strands were nonuniformly distributed and were separated by large and small spaces.
Asunto(s)
Pectinas/química , Citrus sinensis , Geles , Mecánica , Microscopía de Fuerza Atómica , Conformación Molecular , Soluciones , Azúcares Ácidos , AguaRESUMEN
Pectin was acid extracted from orange albedo by steam injection heating under pressure. Extraction times ranged from 2 to 6 min at a pressure of about 15 psi. Solubilized pectin was characterized by HPSEC with online light scattering and viscosity detection. Molar mass (M), radius of gyration (R(g)), and intrinsic viscosity ([eta]) all decreased with increasing extraction time when heating temperature was 120 degrees C. At heating times of 3 min, M(w) ranged from 4.9 to 4.5 x 10(5), R(gz) was about 44 nm, and [eta](w) ranged from 8.4 to 7.9 dL/g. Chromatography revealed that solubilized pectin distributions were bimodal in nature at 3 min extraction time and trimodal when the extraction time was 6 min. Scaling law exponents obtained for the highest molar mass fractions were consistent with a very compact spherical structure. For the intermediate fraction, scaling law exponents were consistent with a less compact spherical structure comparable to a random coil. In the case of the low molar mass fractions, scaling law exponents were consistent with a structure more asymmetric in shape. These results are consistent with earlier results which indicated that pectin distributions were mixtures of two or more of the following due to disaggregation during extraction: spherical aggregates, hydrogen bonded network structures, and partially or fully disaggregated components of network structures which could include branched structures, rods, segmented rods, and kinked rods.
Asunto(s)
Citrus/química , Pectinas/aislamiento & purificación , Cromatografía , Calor , Microondas , Pectinas/química , Presión , VolatilizaciónRESUMEN
A pectin methylesterase (PME) from sweet orange fruit rag tissue, which does not destabilize citrus juice cloud, has been characterized. It is a salt-dependent PME (type II) and exhibits optimal activity between 0.1 and 0.2 M NaCl at pH 7.5. The pH optimum shifted to a more alkaline range as the salt molarity decreased (pH 8.5-9.5 at 50 mM NaCl). It has an apparent molecular mass of 32.4 kDa as determined by gel filtration chromatography, an apparent molecular mass of 33.5 kDa as determined by denaturing electrophoresis, and a pI of 10.1 and exhibits a single activity band after isoelectric focusing (IEF). It has a K(m) of 0.0487 mg/mL and a V(max) of 4.2378 nkat/mg of protein on 59% DE citrus pectin. Deblocking the N-terminus revealed a partial peptide composed of SVTPNV. De-esterification of non-calcium-sensitive pectin by 6.5% increased the calcium-sensitive pectin ratio (CSPR) from 0.045 +/- 0.011 to 0.829 +/- 0.033 but had little, if any, effect on pectin molecular weight. These properties indicate this enzyme will be useful for studying the PME mode of action as it relates to juice cloud destabilization.
Asunto(s)
Hidrolasas de Éster Carboxílico/aislamiento & purificación , Hidrolasas de Éster Carboxílico/metabolismo , Citrus sinensis/enzimología , Frutas/enzimología , Cloruro de Sodio/farmacología , Cromatografía en Gel , Electroforesis en Gel de Poliacrilamida , Concentración de Iones de Hidrógeno , Focalización Isoeléctrica , Punto Isoeléctrico , Isoenzimas/aislamiento & purificación , Isoenzimas/metabolismo , Peso Molecular , Pectinas/metabolismoRESUMEN
A commercial high-methoxy citrus pectin was treated with a purified salt-independent pectin methylesterase (PME) isozyme isolated from Valencia orange peel to prepare a series of deesterified pectins. A series of alkali-deesterified pectins was also prepared at pH 10 under conditions permitting beta-elimination. Analysis of these pectins using high-performance size exclusion chromatography (HPSEC) with on-line multiangle laser light-scattering, differential viscometer, and refractive index (RI) detectors revealed no reduction in weight-average molecular weight (M(w); 150000) in the PME-treated pectin series, whereas a 16% reduction in intrinsic viscosity (IV) occurred below a degree of esterification (DE) of 47%. In contrast, alkali deesterification rapidly reduced both M(w) and IV to less than half of that observed for untreated pectin. PME treatment of a non-calcium-sensitive citrus pectin introduced calcium sensitivity with only a 6% reduction in the DE. Triad blocks of unesterified galacturonic acid were observed in (1)H nuclear magnetic resonance spectra of this calcium-sensitive pectin (CSP). These results demonstrate that the orange salt-independent PME isozyme utilizes a blockwise mode of action. This is the first report of the preparation of a CSP by PME treatment without significant loss of the pectin's M(w) due to depolymerization.