Immobilization of α-transglucosidase on silica-coated magnetic nanoparticles and its application for production of isomaltooligosaccharide from the potato peel.

In this study, the production of isomaltooligosaccharide from potato peel starch was carried out in three steps: liquefaction, saccharification, and transglucosylation. Further, cloning α-transglucosidase gene from Aspergillus niger (GH31 family), transforming into E. coli BL21 (DE3), overexpressing and purifying the resulting protein for the production of α-transglucosidase. The generated α-transglucosidase was then bound with magnetic nanoparticles, which improved reusability up to 5 cycles with more than 60% activity. All the modifications were characterized using the following methods: Fourier transform infra-red analysis, Transmission Electron Microscopy, Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray spectroscopy, X-Ray Diffraction Spectroscopy, Thermogravimetric Analysis, and Dynamic Light Scattering (DLS) analysis. Further, the optimum conditions for transglucosylation were determined by RSM as follows: enzyme-to-substrate ratio 6.9 U g-1, reaction time 9 h, temperature 45 °C, and pH 5.5 with a yield of 70 g l-1 (± 2.1). MALDI-TOF-MS analysis showed DP of the IMOs in ranges of 2-10. The detailed structural characterization of isomaltooligosaccharide by GC-MS and NMR suggested the α-(1 → 4) and α-(1 → 6)-D-Glcp residues as major constituents along with minor α-(1 → 2) and α-(1 → 3) -D-Glcp residues.

Effect of cellulose and starch fatty acid esters addition on microstructure and physical properties of arabinoxylan films.

Arabinoxylan (AX) and cellulose were extracted from wheat straw, whereas starch was extracted from potato peel. Thereafter, cellulose and starch were esterified with lauric, myristic, palmitic and stearic acids to prepare corresponding cellulose (CFAs) and starch fatty acid esters (SFAs) with DS 2.1-2.8. XRD study revealed remarkable loss of crystallinity in cellulose and starch due to fatty acid esterification. The addition of palmitate and stearate esters of cellulose and starch to AX formed laminar film microstructures which limited water vapor permeability whereas films prepared by blending AX with laurate and myristate esters of starch and cellulose were less effective as water vapor barrier due to their non-layer microstructures. The laminar structures also resulted significant reduction in mechanical strength of the composite films. Furthermore, all AX-CFAs and AX-SFAs films were thermally more stable than native composite films. These films might be used to produce industrially useful coating material for food products.

Structural characterization of the heteroxylans from poplar and switchgrass.

Heteroxylans are polysaccharides with a backbone composed of 1,4-linked ß-D-xylosyl residues. In hardwoods some of these xylosyl residues are substituted at O-2 with 4-O-methyl α-D-glucuronic and occasionally with α-D-glucuronic acid. In grasses, the xylan backbone is predominantly substituted with α-L-arabinofuranosyl residues (most often at O-3, but sometimes at O-2). Grass heteroxylan backbone residues may also have small amounts of α-D-glucuronic acid and/or 4-O-methyl α-D-glucuronic acid at O-2. Heteroxylans have a role in maintaining the structural integrity of the cell walls that comprise the bulk of lignocellulosic biomass. Moreover, differences in the molecular features of these hemicellulosic polysaccharides, including their degree of polymerization, degree of branching and spatial arrangement of side chains along the xylan backbone, have been correlated to altered cell wall properties (Izydorczyk MS, Biliaderis CG, Carbohydr Polym 28:33-48, 1995) and the ease with which biomass can be enzymatically converted to fermentable sugars. Thus, understanding the relationship between heteroxylan structure and biomass properties is required to engineer bioenergy crops with improved processing characteristics. In this chapter we describe some of the analytical methods we routinely use to perform in-depth structural analysis of heteroxylans from poplar and switchgrass biomass.