Effect of vapor-phase glutaraldehyde crosslinking on electrospun starch fibers

In this work, we have proven that starch nanofibrous membranes with high tensile strength, water stability and non-cytotoxicity can be produced by electrospinning of starch solution and post-treatment with GTA in vapor phase. GTA vapor phase crosslinking plays a key role in forming water-stable nanofiber membrane and improving the mechanical properties. Comparing with non-crosslinked starch fibers, the crosslinked fibers are increased by nearly 10 times in tensile strength. The crosslinked starch fibrous membranes are non-cytotoxic. They may find applications in the fields of tissue engineering, pharmaceutical therapy and medical.

Covalent immobilization of naringinase for the transformation of a flavonoid

Naringinase (EC 3.2.1.40) from Penicillium sp was immobilized by covalent binding to woodchips to improve its catalytic activity. The immobilization of naringinase on glutaraldehyde-coated woodchips (600 mg woodchips, 10 U naringinase, 45 °C, pH 4.0 and 12h) through 1% glutaraldehyde cross-linking was optimized. The pH-activity curve of the immobilized enzyme shifted toward a lower pH compared with that of the soluble enzyme. The immobilization caused a marked increase in thermal stability of the enzyme. The immobilized naringinase was stable during storage at 4 °C. No loss of activity was observed when the immobilized enzyme was used for seven consecutive cycles of operations. The efficiency of immobilization was 120%, while soluble naringinase afforded 82% efficacy for the hydrolysis of standard naringin under optimal conditions. Its applicability for debittering kinnow mandarin juice afforded 76% debittering efficiency. 

Cellular localization of water soluble, allergenic proteins in rye-grass (Lolium perenne) pollen using monoclonal and specific IgE antibodies with immunogold probes

A postembedding method has been developed for localizing water soluble allergens in rye-grass pollen. This uses dry fixation in glutaraldehyde vapour, followed by 2,2-dimethoxypropane, prior to a 100% ethanol series leading into embedment in LR Gold. This has allowed the attachment of specific monoclonal antibodies to the allergen, which are themselves probed with specific immunogold labels to the antibodies. Wall and cytoplasmic sites have been identified, representing an improvement of fixation and localization of allergens over previous studies employing polyclonal, broad spectrum antibodies.

Rye-grass allergens are labelled in mature pollen grains in the exine (tectum, nexine and central chamber), and in the electron opaque areas of the cytoplasm, especially mitochondria. The allergens are absent from the intine, polysaccharide (P) particles, amyloplasts, Golgi bodies and endoplasmic reticulum. IgE antibodies derived from humans allergic to rye-grass pollen, bind to similar sites in the cytoplasm but only to the outer surface of the pollen grain wall. This method now provides a valuable tool for further developmental studies on the pollen grains, in order to establish the site/s of synthesis of the allergens.

Ultrastructural analysis of plastids in angiosperm pollen tubes

When Rhododendron pollen tubes are cultured in the dark, electron-dense bodies are present that appear to be a metabolically altered form of a proplastid that is difficult to fix for electron microscopy, and whose membranes may not be intact. When similar pollen tubes are cultured in a dark/light regime, ultrastructurally well-defined proplastids are present after fixation in glutaraldehyde with PIPES buffer and tannic acid, followed by osmic acid. This fixation technique also gave the best ultrastructural images of those proplastids in pollen tubes grown in the dark. Pollen tube plastids have the potential to become chromoplasts when cultured in a dark/light regime as evidenced by the presence of branched tubules characteristic of these organelles. Light appears to be a hitherto neglected environmental factor involved in regulating pollen tube growth. This improved fixation procedure demonstrates the bilayered nature of the membranes surrounding sperm cells and the existence of cytoplasmic channels connecting sperm cell and pollen tube plasma membranes.

Quick and low cost immobilization of proteinases on polyesters: comparison of lactobacilli cell-envelope proteinase and trypsin for protein degradation

Cell-envelope proteinases (CEPs) are a class of proteolytic enzymes produced by lactic acid bacteria and have several industrially relevant applications. However, soluble CEPs are economically unfavorable for such applications due to their poor stability and lack of reusability. In a quest to prepare stable biocatalysts with improved performance, CEP from Lactobacillus delbrueckii subsp. lactis 313 and trypsin (as a model enzyme) were immobilized onto nonwoven polyester fabrics in a three-step protocol including ethylenediamine activation and glutaraldehyde crosslinking. Immobilization gave protein loading yields of 21.9% (CEP) and 67.7% (trypsin) while residual activity yields were 85.6% (CEP) and 4.1% (trypsin). The activity of the immobilized enzymes was dependent on pH, but was retained at elevated temperatures (40-70°C). An increase in Km values was observed for both enzymes after immobilization. After 70 days of storage, the immobilized CEP retained ca. 62% and 96% of initial activity when the samples were stored in a lyophilized form at -20°C or in a buffer at 4°C, respectively. Both immobilized CEP and trypsin were able to hydrolyze proteins such as casein, skimmed milk proteins and bovine serum albumin. This immobilization protocol can be used to prepare immobilized biocatalyst for various protein degradation processes.

Studies on the crosslinking of electrospun starch nanofibers

The starch nanofiber mats were prepared by electrospinning, and crosslinked by deal with glutaraldehyde vapor in a sealed containers. The morphology and structure of the fibers (before and after crosslinking) were characterized by SEM and FT-IR, and the properties of the product were measured by tensile test and contact angle measurements. Test results show that, acetalization reaction occurred between the intermolecular of glutaraldehyde and starch, the morphology of crosslinked fibers can be grossly preserved compared with the uncrosslinked starch fibers, and tensile properties and water resistance of the fiber mats have been greatly improved after glutaraldehyde crosslinking.

Evaluation of cross-linked enzyme aggregates of Lactobacillus cell-envelope proteinases, for protein degradation

Enzymatic hydrolysis is a widely used approach to improve the functional, nutritionaland physiological properties of food proteins. In this study, cross-linked enzyme aggre-gates (CLEAs) have been prepared from cell-envelope proteinases (CEPs) of Lactobacillusdelbrueckii subsp. lactis 313 and their proteolytic properties have been evaluated using severalfood proteins. We have optimized cross-linking conditions including ammonium sulphateconcentration, incubation temperatures, agitation speed, glutaraldehyde cross-linker con-centration, reaction time and the addition of proteic feeders. Particularly, the presence ofBSA improves retained activity of cross-linked CEP aggregates (CLCEPAs) from 21.5% to 40.9%.Blocking unreacted cross-linking groups on aggregates is important to enhance recyclabil-ity of CLCEPAs. CLCEPAs had attractive thermal stability at 50◦C and it showed enhancedcatalytic activity over long-term storage after lyophilization. We have demonstrated thatCLCEPAs has proteolytic properties on different food proteins including complex (chickenegg albumin, skimmed-milk protein), fractionated (bovine casein, whey protein isolate), andpurified (bovine serum albumin) proteins. Being the first report of CLEAs from lactobacilliCEPs, this study demonstrates the feasibility of using LDL 313 CLCEPAs for degradation ofvarious food proteins.

Microencapsulation of flaxseed oil in flaxseed protein and flaxseed gum complex coacervates

Flaxseed oil, a rich source of omega-3 fatty acids, was microencapsulated in a novel matrix formed by complex coacervation between flaxseed protein isolate (FPI) and flaxseed gum (FG). This matrix was crosslinking with glutaraldehyde. Liquid microcapsules with three core (oil)-to-wall ratios (1:2, 1:3 and 1:4) were prepared and spray-dried or freeze-dried to produce powders. The microencapsulation efficiency, surface oil, morphology and oxidative stability of these microcapsules were determined. The spray-dried solid microcapsules had higher oil microencapsulation efficiency, lower surface oil content, smoother surface morphology and higher oxidation stability than the freeze-dried microcapsules. The highest microencapsulation efficiency obtained in spray-dried microcapsules was 87% with a surface oil of 2.78% at core-to-wall ratio 1:4 and oil load 20%. The oxidation stability obtained from spray-dried microcapsules at core-to-wall ratio of 1:4 was nearly double that of the unencapsulated flaxseed oil.