Cellulose constitutes the most abundant renewable polymer resource available today. As a chemical raw material, it is generally well-known that it has been used in the form of fibers or derivatives for nearly 150 years for a wide spectrum of products and materials in daily life. What has not been known until relatively recently is that when cellulose fibers are subjected to acid hydrolysis, the fibers yield defect-free, rod-like crystalline residues. Cellulose nanocrystals (CNs) have garnered in the materials community a tremendous level of attention that does not appear to be relenting. These biopolymeric assemblies warrant such attention not only because of their unsurpassed quintessential physical and chemical properties (as will become evident in the review) but also because of their inherent renewability and sustainability in addition to their abundance. They have been the subject of a wide array of research efforts as reinforcing agents in nanocomposites due to their low cost, availability, renewability, light weight, nanoscale dimension, and unique morphology. Indeed, CNs are the fundamental constitutive polymeric motifs of macroscopic cellulosic-based fibers whose sheer volume dwarfs any known natural or synthetic biomaterial. Biopolymers such as cellulose and lignin and † North Carolina State University. ‡ Helsinki University of Technology. Dr. Youssef Habibi is a research assistant professor at the Department of Forest Biomaterials at North Carolina State University. He received his Ph.D. in 2004 in organic chemistry from Joseph Fourier University (Grenoble, France) jointly with CERMAV (Centre de Recherche sur les Macromolecules Vegetales) and Cadi Ayyad University (Marrakesh, Morocco). During his Ph.D., he worked on the structural characterization of cell wall polysaccharides and also performed surface chemical modification, mainly TEMPO-mediated oxidation, of crystalline polysaccharides, as well as their nanocrystals. Prior to joining NCSU, he worked as assistant professor at the French Engineering School of Paper, Printing and Biomaterials (PAGORA, Grenoble Institute of Technology, France) on the development of biodegradable nanocomposites based on nanocrystalline polysaccharides. He also spent two years as postdoctoral fellow at the French Institute for Agricultural Research, INRA, where he developed new nanostructured thin films based on cellulose nanowiskers. Dr. Habibi’s research interests include the sustainable production of materials from biomass, development of high performance nanocomposites from lignocellulosic materials, biomass conversion technologies, and the application of novel analytical tools in biomass research. Chem. Rev. 2010, 110, 3479–3500 3479

Cellulose nanocrystals: chemistry, self-assembly, and applications.

https://yunus.hacettepe.edu.tr/~damlacetin/kmu407/index_dosyalar/4.%20makale.pdf

Biodegradable polymers as biomaterials

Polymers are the compounds that includes platics, artificial fibers, rubber, cellulose, and many other materials, including coatings and adhesives. This book presents key data on approximately 200 important polymers currently in industrial use or under study in industrial or academic research. No other single source covers so many polymers or offers such a depth of data. The book standardizes and makes accessible a wealth of essential data for students, teachers, researchers, and other professionals in chemistry and chemical engineering.

Polymer Data Handbook

BACKGROUND: Butyrate, a short-chain fatty acid, is a main end-product of intestinal microbial fermentation of mainly dietary fibre. Butyrate is an important energy source for intestinal epithelial cells and plays a role in the maintenance of colonic homeostasis. AIM: To provide an overview on the present knowledge of the bioactivity of butyrate, emphasizing effects and possible mechanisms of action in relation to human colonic function. METHODS: A PubMed search was performed to select relevant publications using the search terms: 'butyrate, short-chain fatty acid, fibre, colon, inflammation, carcinogenesis, barrier, oxidative stress, permeability and satiety'. RESULTS: Butyrate exerts potent effects on a variety of colonic mucosal functions such as inhibition of inflammation and carcinogenesis, reinforcing various components of the colonic defence barrier and decreasing oxidative stress. In addition, butyrate may promote satiety. Two important mechanisms include the inhibition of nuclear factor kappa B activation and histone deacetylation. However, the observed effects of butyrate largely depend on concentrations and models used and human data are still limited. CONCLUSION: Although most studies point towards beneficial effects of butyrate, more human in vivo studies are needed to contribute to our current understanding of butyrate-mediated effects on colonic function in health and disease.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2036.2007.03562.x

Review article: the role of butyrate on colonic function

Fibroblasts can condense a hydrated collagen lattice to a tissue-like structure 1/28th the area of the starting gel in 24 hr. The rate of the process can be regulated by varying the protein content of the lattice, the cell number, or the con- centration of an inhibitor such as Colcemid. Fibroblasts of high population doubling level propagated in vitro, which have left the cell cycle, can carry out the contraction at least as efficiently as cycling cells. The potential uses of the system as an immu- nologically tolerated "tissue" for wound hea ing and as a model for studying fibroblast function are discussed.

Production of a tissue-like structure by contraction of collagen lattices by human fibroblasts of different proliferative

Properties of sheared carrageenan/milk gels. Effect of the presence of nu precursors in iota-carrageenan

Classification of natural gums. V. Identification of commercial gum arabic from Africa by Euclidean modelling

Acacia polyacantha was fractionated by a successive non-solvent fractionation technique, using ethanol and acetone separately as fractionating solvent. Four different fractions were obtained and labelled PO-E1F – PO-E4F and PO-A1F – PO-A4F in ethanol and acetone respectively. The whole gum and the fractions were fully characterised to determine the moisture, ash, pH, molecular weight, number average molecular weight, nitrogen content, intrinsic viscosity, emulsification performance and stability. The results for the fractions in both solvents showed lower moisture content, optical rotation and intrinsic viscosity while the uronic acid content was higher in all fractions apart from PO-A3F. The protein distribution associated with the high molecular weight fraction varied according to the fractionation step and solvent. The highest molecular weight was obtained for PO-E4F while the remaining fractions showed lower molecular weight compared to the control. All acetone fractions gave higher molecular weight compared to the control. The emulsification performance and stability was largely dependent on the protein distribution and its association with the higher molecular weight fractions. PO-E3F and PO-A4F gave better emulsification performance and stability than the control. PO-A4F gave results comparable to A. senegal.

Characterisation, Fractionation and Emulsification Properties of Acacia Polyacantha Gums

Mixed biopolymer solutions and gels have wide applications in the modern Food Industry. Considerable progress has already been made in scientific studies of these, but there remains a significant gap between the model systems employed in such investigations, and the materials of most practical importance. Real food products have generally a more complex composition, involving at least three types of biopolymers, in contrast to the binary mixtures usually treated in academic work. These complex biopolymer mixtures are generally used to achieve the required physical structure, perceived texture quality, and behaviour during processing. The influence of extra ingredients such as extra polymers is often seen simply as a perturbation, but this is unlikely to be generally true. While some of these mixed systems behave as one could expect from the known properties of their individual components, in other cases, the properties are shifted relative to those of the components alone, or are qualitatively different. The purpose of the present study is to advance knowledge of the implications of adding extra biopolymer components to a binary mixed system, in terms of kinetic, structural, and mechanical properties of the biomaterials formed. As a starting point, three polysaccharides have been chosen to investigate these aspects: an aqueous solution of agarose and κ-carrageenan as the mixed system, and gellan as an extra biopolymer. Parameters such as polymer concentration, ionic strength, nature of the counterions, and temperature profiles, have been taken into account. In order to investigate possible interactions between these polymers and implications for the resulting gels, a range of experimental approaches were used. From microscopic level to macroscopic behaviour, techniques such as optical rotation, turbidity measurements, DSC, and rheology have been used extensively. For brevity, only selected results are shown here.

Glyn O. Phillips

Papers

Properties of sheared carrageenan/milk gels. Effect of the presence of nu precursors in iota-carrageenan

Classification of natural gums. V. Identification of commercial gum arabic from Africa by Euclidean modelling

Characterisation, Fractionation and Emulsification Properties of Acacia Polyacantha Gums

Multicomponent biopolymer gels: The agarose-carrageenan-gellan system

Laser flash and steady-state photolysis of benoxaprofen in solution: relevance to singlet oxygen production