Structure of the 4-O-[1-Carboxyethyl]-d-Mannose-Containing O-Specific Polysaccharide of a Halophilic Bacterium Salinivibrio sp. EG9S8QL

The moderately halophilic strain Salinivibrio sp. EG9S8QL was isolated among 11 halophilic strains from saline mud (Emisal Salt Company, Lake Qarun, Fayoum, Egypt). The lipopolysaccharide was extracted from dried cells of Salinivibrio sp. EG9S8QL by the phenol–water procedure. The OPS was obtained by mild acid hydrolysis of the lipopolysaccharide and was studied by sugar analysis along with 1H and 13C NMR spectroscopy, including 1H,1H COSY, TOCSY, ROESY, 1H,13C HSQC, and HMBC experiments. The OPS was found to be composed of linear tetrasaccharide repeating units of the following structure: →2)-β-Manp4Lac-(1→3)-α-ManpNAc-(1→3)-β-Rhap-(1→4)-α-GlcpNAc-(1→, where Manp4Lac is 4-O-[1-carboxyethyl]mannose.

A New Look at the Enterobacterial Common Antigen Forms Obtained during Rough Lipopolysaccharides Purification

Enterobacterial common antigen (ECA) is a conserved antigen expressed by enterobacteria. It is built by trisaccharide repeating units: →3)-α-D-Fucp4NAc-(1→4)-β-D-ManpNAcA-(1→4)-α-D-GlcpNAc-(1→ and occurs in three forms: as surface-bound linear polysaccharides linked to a phosphoglyceride (ECAPG) or lipopolysaccharide − endotoxin (ECALPS), and cyclic form (ECACYC). ECA maintains, outer membrane integrity, immunogenicity, and viability of enterobacteria. A supernatant obtained after LPS ultracentrifugation was reported as a source for ECA isolation, but it has never been assessed for detailed composition besides ECACYC. We used mild acid hydrolysis and gel filtration, or zwitterionic-hydrophilic interaction liquid (ZIC®HILIC) chromatography combined with mass spectrometry for purification, fractionation, and structural analysis of rough Shigella sonnei and Escherichia coli R1 and K12 crude LPS preparations. Presented work is the first report concerning complex characteristic of all ECA forms present in LPS-derived supernatants. We demonstrated high heterogeneity of the supernatant-derived ECA that contaminate LPS purified by ultracentrifugation. Not only previously reported O-acetylated tetrameric, pentameric, and hexameric ECACYC have been identified, but also devoid of lipid moiety linear ECA built from 7 to 11 repeating units. Described results were common for all selected strains. The origin of linear ECA is discussed against the current knowledge about ECAPG and ECALPS.

Extraction of Cellulose Nanofibers via Eco-friendly Supercritical Carbon Dioxide Treatment Followed by Mild Acid Hydrolysis and the Fabrication of Cellulose Nanopapers

The conventional isolation of cellulose nanofibers (CNFs) process involves high energy input which leads to compromising the pulp fiber’s physical and chemical properties, in addition to the issue of elemental chlorine-based bleaching, which is associated with serious environmental issues. This study investigates the characteristic functional properties of CNFs extracted via total chlorine-free (TCF) bleached kenaf fiber followed by an eco-friendly supercritical carbon dioxide (SC-CO2) treatment process. The Fourier transmission infra-red FTIR spectra result gave remarkable effective delignification of the kenaf fiber as the treatment progressed. TEM images showed that the extracted CNFs have a diameter in the range of 10–15 nm and length of up to several micrometers, and thereby proved that the supercritical carbon dioxide pretreatment followed by mild acid hydrolysis is an efficient technique to extract CNFs from the plant biomass. XRD analysis revealed that crystallinity of the fiber was enhanced after each treatment and the obtained crystallinity index of the raw fiber, alkali treated fiber, bleached fiber, and cellulose nanofiber were 33.2%, 54.6%, 88.4%, and 92.8% respectively. SEM images showed that amorphous portions like hemicellulose and lignin were removed completely after the alkali and bleaching treatment, respectively. Moreover, we fabricated a series of cellulose nanopapers using the extracted CNFs suspension via a simple vacuum filtration technique. The fabricated cellulose nanopaper exhibited a good tensile strength of 75.7 MPa at 2.45% strain.

The Effect of Acid Hydrolysis Treatment on the Production of Nanocellulose Based on Oil Palm Empty Fruit Bunches

Nanocellulose has been known as promising reinforcing material in various polymer based product resulted to remarkable improvement in mechanical and thermal properties. Hence, studies to date have developed and explored various sources of biomass to produce nanocellulose. The aims of this study are to synthesize and fully characterize nanocellulose obtained from abundantly available oil palm empty fruit bunches via two different methods which are strong (H2SO4) and mild acid (H3PO4) hydrolysis at 50 °C for 3.5 hours. Based on the morphological study using Transmission Electron Microscopy, rod like nanocellulose was obtained using strong acid hydrolysis while mild acid hydrolysis produced long filament shape. X-Ray diffraction analysis showed that the degree crystallinity of nanocellulose produced from strong acid hydrolysis was higher which is 96% than that of mild acid hydrolysis recorded with 86%. While the sulphuric acid hydrolysis usually produces lower thermal stability than that of other types acid hydrolysis, surprisingly, in this study, the thermal stability of nanocellulose from strong acid hydrolysis was relatively similar to mild acid hydrolysis due to the formation of single crystal structure affording unique characteristic of the obtained nanocellulose.