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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Evaluation of β-galactosidase from Lactobacillus acidophilus as biocatalyst for galacto-oligosaccharides synthesis: Product structural characterization and enzyme immobilization

β-Galactosidase is an important industrial enzyme that catalyzes reaction of lactose hydrolysis and recently more interesting reaction of transgalactosylation, yielding a highly valuable group of prebiotic compounds named galacto-oligosaccharides (GOS). In this paper, parameters for achieving high yields of tailor-made GOS using crude β-galactosidase obtained from Lactobacillus acidophilus ATCC 4356, probiotic bacteria regarded as safe for human consumption, were optimized. At the same time, detailed structural elucidation of obtained GOS was conducted, and it was concluded that β-galactosidase from L. acidophilus shows a particular specificity towards the formation of β-(1 → 6) glycosidic bonds. In order to develop more stable and economically cost-effective preparation, crude enzyme was successfully immobilized on a methacrylic polymer carrier Lifetech ECR8409, leading to its simultaneous 2-fold purification. In conclusion, this immobilized preparation showed unchanged specificity towards the transgalactosylation reaction, thus yielding 86 g/l GOS under the previously optimized conditions (lactose concentration 400 g/l in 0.1 M sodium phosphate buffer, pH 6.8 and temperature 50°C).

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Chitosan oligosaccharides enhance lipid droplets via down-regulation of PCSK9 gene expression in HepG2 cells

Highlights: • COS enhance lipid droplets in HepG2 cells. • COS down-regulate the expression of PCSK9 to maintain hepatic LDLR abundance and activity. • COS inhibit HNF1α and SREBP-2 activity leading to down-regulation of PCSK9. Chitosan oligosaccharides (COS), linear polymers of N-acetyl-D-glucosamine and deacetylated glucosamine, exhibit diverse pharmacological effects such as antimicrobial, antitumor, antioxidant and anti-inflammatory activities. Here, we explored their hypocholesterolemic effects in vivo and the molecular mechanisms of COS in hepatic cells. Our in vivo study of dyslipidemic ApoE{sup -/-} male mice showed that COS treatment of 500 mg kg{sup −1} d{sup −1} for 4 weeks clearly reduced the lipid deposits in the aorta and significantly decreased the hepatic proprotein convertase subtilisin/kexin type 9 (PCSK9) protein levels versus HFD groups (p < 0.05). To elucidate the mechanisms behind these effects, the HepG2 cell line was treated with COS. We found that COS (200 μg/ml) increased the amount of cell-surface low-density lipoprotein receptor (LDLR) and enhanced the lipid droplets in HepG2 cells (p < 0.05). The mRNA levels of LDLR and HMG-CoA protein levels were not altered, and the mRNA levels of PCSK9 were down-regulated by COS treatment for 24 h. We also observed that the expression levels of SREBP-2 (125 kD) and HNF-1α were increased in total cell lysates, but nuclear SREBP-2 (nSREBP-2, 68 kD, the active subunit of SREBP-2) levels were decreased and FOXO3a levels increased in nuclear lysates after COS treatment for 24 h. We demonstrated that one of the reasons for regulation of lipid transfer with COS is that FOXO3a levels are up-regulated by COS, leading to a reduction in the PCSK9 promoter binding capacity of HNF-1α and thus suppressing PCSK9 gene expression, up-regulating LDLR levels, and enhancing the lipid droplets in HepG2 cells. In addition, decreased expression of the PCSK9 gene was also contributed to by down-regulation of SREBP-2 by COS. We further confirmed the effect of suppression of PCSK9 expression by COS by utilizing RNA interference to silence HNF-1α and SREBP-2. Finally, to the best of our knowledge, we are the first to demonstrate that PCSK9 expression and LDLR activity are synergistically changed by a combination of HNF-1α and SREBP-2 after COS treatment. Our findings indicate that COS may regulate PCSK9 to modulate hepatic LDLR abundance and activity.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

The interactivity of sources and dietary levels of resistant starches – impact on growth performance, starch, and nutrient digestibility, digesta oligosaccharides profile, cecal microbial metabolites, and indicators of gut health in broiler chickens

In a 21-d study, 480 Cobb 500 (off-sex) male broiler chicks were used to investigate the effects of feeding different sources and levels of resistant starches (RS) on growth performance, nutrient and energy utilization, and intestinal health in broiler chickens. The birds were allocated to 10 dietary treatments in a 3 × 3 + 1 factorial arrangement. The factors were 3 RS-sources (RSS): banana starch (BS), raw potato starch (RPS), and high-amylose corn starch (HCS); each at 3 levels (RSL) 25, 50, or 100 g/kg plus a corn-soybean meal control diet. Birds and feed were weighed on d 0, 8, and 21. On d 21, samples of jejunal tissue and digesta were collected for chemical analysis. Data were analyzed using the mixed model procedure of JMP with factor levels nested with the control. In the 0 to 21 phase, the birds fed the RPS diets had higher (P = 0.011) FI than those fed HCS or control diets, and FCR was greater (P = 0.030) in birds that received BS diets than in other diets. RSS × RSL was significant (P < 0.05) for total tract nutrient retention, AME, and AMEn on d 21. The starch digestibility was higher (P < 0.001) in birds that received the control diet than in RS diets, and decreased as RS levels increased, except for HCS. The apparent metabolizable energy (AME) and nitrogen-corrected AME (AMEn) were higher (P < 0.001) in birds fed 100 g/kg HCS diet, with both decreasing with increasing levels of BS and RPS, except for HCS. Relative ileal oligosaccharides profile showed significant (P < 0.05) RSS × RSL with a higher relative abundance of Hex(3) (P = 0.01) and Pent(3) (P = 0.001) in HCS diets. In conclusion, RS may influence gut health and growth performance in broiler chickens through modulation of cecal SCFA and nutrient digestion, but these depend largely on the botanical origin and concentrations of individual RS.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Nonconventional NMR Spin-Coupling Constants in Oligosaccharide Conformational Modeling: Structural Dependencies Determined from Density Functional Theory Calculations

Nonconventional NMR spin-coupling constants were investigated to determine their potential as conformational constraints in MA’AT modeling of the O-glycosidic linkages of oligosaccharides. Four ( 1 J C1',H1' , 1 J C1',C2' , 2 J C1',H2' , and 2 J C2',H1' ) and eight ( 1 J C4,H4 , 1 J C3,C4 , 1 J C4,C5 , 2 J C3,H4 , 2 J C4,H3 , 2 J C5,H4 , 2 J C4,H5 , and 2 J C3,C5 ) spin-couplings in methyl β-d-galactopyranosyl-(1→4)-β-d-glucopyranoside (methyl β-lactoside) were calculated using density functional theory (DFT) to determine their dependencies on O-glycosidic linkage C–O torsion angles, $\phi$ and ψ, respectively. Long-range 4 J H1',H4 was also examined as a potential conformational constraint of either $\phi$ or ψ. Secondary effects of exocyclic (hydroxyl) C–O bond rotation within or proximal to these coupling pathways were investigated. Based on the findings of methyl β-lactoside, analogous J-couplings were studied in five additional two-bond O-glycosidic linkages [βGlcNAc-(1→4)-βMan, 2-deoxy-βGlc-(1→4)-βGlc, αMan-(1→3)-βMan, αMan-(1→2)-αMan, and βGlcNAc(1→2)-αMan] to determine whether the coupling behaviors observed in methyl β-lactoside were more broadly observed. Of the 13 nonconventional J-couplings studied, 7 exhibit properties that may be useful in future MA’AT modeling of O-glycosidic linkages, none of which involve coupling pathways that include the linkage C–O bonds. The findings also provide new insights into the general effects of exocyclic C–O bond conformation on the magnitude of experimental spin-couplings in saccharides and other hydroxyl-containing molecules.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Mapping periplasmic binding protein oligosaccharide recognition with neutron crystallography

Numerous studies have shown how periplasmic binding proteins (PBPs) bind substrates with exquisite specificity, even distinguishing between sugar epimers and anomers, or structurally similar ions. Yet, marked substrate promiscuity is also a feature encoded in some PBPs. Except for three sub-Ångström crystal structures, there are no reports of hydrogen atom positions in the remaining (> 1000) PBP structures. The previous X-ray crystal structure of the maltodextrin periplasmic-binding protein from Thermotoga maritima (tmMBP) complexed with oligosaccharide showed a large network of interconnected water molecules stretching from one end of the substrate binding pocket to the other. These water molecules are positioned to form multiple hydrogen bonds, as well as forming interactions between the protein and substrate. Here we present the neutron crystal structure of tmMBP to a resolution of 2.1 Å. This is the first neutron crystal structure from the PBP superfamily and here we unambiguously identify the nature and orientation of the hydrogen bonding and water-mediated interactions involved in stabilizing a tetrasaccharide in the binding site. More broadly, these results demonstrate the conserved intricate mechanisms that underlie substrate-specificity and affinity in PBPs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Engineered plants provide a photosynthetic platform for the production of diverse human milk oligosaccharides

Human milk oligosaccharides (HMOs) are a diverse class of carbohydrates which support the health and development of infants. The vast health benefits of HMOs have made them a commercial target for microbial production; however, producing the approximately 200 structurally diverse HMOs at scale has proved difficult. Here we produce a diversity of HMOs by leveraging the robust carbohydrate anabolism of plants. This diversity includes high-value and complex HMOs, such as lacto-N-fucopentaose I. HMOs produced in transgenic plants provided strong bifidogenic properties, indicating their ability to serve as a prebiotic supplement with potential applications in adult and infant health. Technoeconomic analyses demonstrate that producing HMOs in plants provides a path to the large-scale production of specific HMOs at lower prices than microbial production platforms. Our work demonstrates the promise in leveraging plants for the low-cost and sustainable production of HMOs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Profile of Twenty-Three Human Milk Oligosaccharides in Han Chinese Mothers throughout Postpartum 1 year

Human milk oligosaccharides (HMOs) are multifunctional carbohydrates in breast milk, which are composed by a variety of structures. This study aimed to identified HMOs concentration profile, milk microbiota composition, and the associations with major maternal characteristics in Han Chinese mothers in the one-year lactation period. Seventeen healthy mothers aged from 28 to 36 years, who gave birth to healthy term infants, were recruited. Carbohydrates were detected using the MIRIS human milk analyzer (HMA), and twenty-three HMOs were quantified using ultra-performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS). Results showed that carbohydrates were relatively stable, while total HMO concentrations ranged from 1.74 to 9.72 g/L and decreased gradually over lactation in breast milk. Based on the structure, seven sialylated HMOs concentration showed the significant decline ( p < 0.05 ) after three months in lactation. In addition, the relationships between maternal factors, containing the lactation period, genetic status, delivery mode, parity, and milk microbiota profile, and the HMO composition in healthy women, which still need further investigations, were observed.

Xun, Yiping↗
DOE OSTI2022

Transcriptional regulation of the raffinose family oligosaccharides pathway in Sorghum bicolor reveals potential roles in leaf sucrose transport and stem sucrose accumulation

Bioenergy sorghum hybrids are being developed with enhanced drought tolerance and high levels of stem sugars. Raffinose family oligosaccharides (RFOs) contribute to plant environmental stress tolerance, sugar storage, transport, and signaling. To better understand the role of RFOs in sorghum, genes involved in myo -inositol and RFO metabolism were identified and relative transcript abundance analyzed during development. Genes involved in RFO biosynthesis ( SbMIPS1, SbInsPase, SbGolS1, SbRS ) were more highly expressed in leaves compared to stems and roots, with peak expression early in the morning in leaves. SbGolS, SbRS, SbAGA1 and SbAGA2 were also expressed at high levels in the leaf collar and leaf sheath. In leaf blades, genes involved in myo -inositol biosynthesis ( SbMIPS1, SbInsPase ) were expressed in bundle sheath cells, whereas genes involved in galactinol and raffinose synthesis ( SbGolS1, SbRS ) were expressed in mesophyll cells. Furthermore, SbAGA1 and SbAGA2 , genes that encode neutral-alkaline alpha-galactosidases that hydrolyze raffinose, were differentially expressed in minor vein bundle sheath cells and major vein and mid-rib vascular and xylem parenchyma. This suggests that raffinose synthesized from sucrose and galactinol in mesophyll cells diffuses into vascular bundles where hydrolysis releases sucrose for long distance phloem transport. Increased expression (>20-fold) of SbAGA1 and SbAGA2 in stem storage pith parenchyma of sweet sorghum between floral initiation and grain maturity, and higher expression in sweet sorghum compared to grain sorghum, indicates these genes may play a key role in non-structural carbohydrate accumulation in stems.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Facile Labeling of Sieve Element Phloem-Protein Bodies Using the Reciprocal Oligosaccharide Probe OGA488

Sieve elements of many angiosperms contain structural phloem proteins (P-proteins) that can interact to create large P-protein bodies. P-protein bodies can occlude sieve plates upon injury but the range of functional and physiological roles of P-proteins remains uncertain, in part because of challenges in labeling and visualization methods. Here, we show that a reciprocal oligosaccharide probe, OGA 488 , can be used in rapid and sensitive labeling of P-protein bodies in Arabidopsis, poplar, snap bean and cucumber in histological sections. OGA 488 labeling of knockouts of the two Arabidopsis P-protein-encoding genes, AtSEOR1 and AtSEOR2 , indicated that labeling is specific to AtSEOR2. That protein bodies were labeled and visible in Atseor1 knockouts indicates that heterodimerization of AtSEOR1 and AtSEOR2 may not be necessary for P-protein body formation. Double labeling with a previously characterized stain for P-proteins, sulphorhodamine 101, confirmed P-protein labeling and also higher specificity of OGA 488 for P-proteins. OGA 488 is thus robust and easily used to label P-proteins in histological sections of multiple angiosperm species.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Crystallographic structure and molecular dynamics simulations of the major endoglucanase from Xanthomonas campestris pv. campestris shed light on its oligosaccharide products release pattern

Cellulases are critical enzymatic components for the transformation of plant biomass into fuels, renewable materials and green chemicals. In this work, we determined the crystal structure, pattern of hydrolysis products release, and conducted molecular dynamics simulations of the major endoglucanase from the Xanthomonas campestris pv. campestris (XccCel5A). XccCel5A has a TIM barrel fold with the catalytic site centrally placed in a binding groove surrounded by aromatic side chains. Molecular dynamics simulations show that productive position of the substrate is secured by a network of hydrogen bonds in the four main subsites, which differ in details from homologous structures. Capillary zone electrophoresis and computational studies reveal XccCel5A can act both as endoglucanase and licheninase, but there are preferable arrangements of substrate regarding β-1,3 and β-1,4 bonds within the binding cleft which are related to the enzymatic efficiency.

59 BASIC BIOLOGICAL SCIENCES↗