Biochemical characterisation of cellulose and cell-wall-matrix polysaccharides in variously oxidised sugar-beet pulp preparations differing in viscosity.

Sugar-beet pulp (SBP) is an abundant, cellulose-rich, non-food by-product of agriculture. Oxidised SBP (oP) has valuable viscosity attributes, and different oxidation protocols yield higher- or lower-viscosity oP. We investigated how SBP polysaccharides change during oxidation, since these changes must define oP quality. Oxidation solubilised much pectin and hemicellulose; however, most cellulose stayed insoluble. Fresh SBP contains negligible 'hemicellulose a' (=alkali-extractable polysaccharides that precipitate upon acidification), but oxidation created abundant glucose-rich 'hemicellulose a' from SBP cellulose. We propose that the cellulose acquired COOH groups, conferring alkali-extractability and admitting more water, thereby augmenting viscosity. The pectin and hemicellulose molecules that were retained during oxidation had been partially depolymerised, and their median Mr correlated negatively with oP viscosity. We developed a novel procedure to explore cellulose's permeability by measuring the ingress of tritium from [3H]water into microfibrils and its retention during desiccation. In high-crystallinity Avicel, 75 % of the cellulose's OH groups were inaccessible to [3H]water, whereas filter-paper cellulose acquired the theoretical maximum 3H, indicating an open structure. Retention of 3H by oP preparations correlated positively with viscosity, indicating that increased cellulose accessibility generates a viscous oP. In conclusion, depolymerisation and solubilisation of matrix polysaccharides, accompanied by increasing water-accessibility of cellulose, enhanced SBP's viscosity.

Valorization of sugar beet pulp to value-added products: A review.

The processing of sugar beet in the sugar production industry releases huge amounts of sugar beet pulp as waste which can be considered a valuable by-product as a source of cellulose, hemicellulose, and pectin. Valorization of sugar beet pulp into value added products occurs through acid hydrolysis, hydrothermal techniques, and enzymatic hydrolysis. Biochemical conversion of beet pulp into simple fermentable sugars for producing value added products occurs through enzymatic hydrolysis is a cost effective and eco-friendly process. While beet pulp has predominantly been used as a fodder for livestock, recent developments in its biotechnological valorization have unlocked its value as a feedstock in the production of biofuels, biohydrogen, biodegradable plastics, and platform chemicals such as lactic acid, citric acid, alcohols, microbial enzymes, single cell proteins, and pectic oligosaccharides. This review brings forward recent biotechnological developments made in the valorization of sugar beet pulp into valuable products.

Virus-Like Particle Facilitated Deposition of Hydroxyapatite Bone Mineral on Nanocellulose after Exposure to Phosphate and Calcium Precursors.

We produced and isolated tobacco mosaic virus-like particles (TMV VLPs) from bacteria, which are devoid of infectious genomes, and found that they have a net negative charge and can bind calcium ions. Moreover, we showed that the TMV VLPs could associate strongly with nanocellulose slurry after a simple mixing step. We sequentially exposed nanocellulose alone or slurries mixed with the TMV VLPs to calcium and phosphate salts and utilized physicochemical approaches to demonstrate that bone mineral (hydroxyapatite) was deposited only in nanocellulose mixed with the TMV VLPs. The TMV VLPs confer mineralization properties to the nanocellulose for the generation of new composite materials.

Nanofibers Produced from Agro-Industrial Plant Waste Using Entirely Enzymatic Pretreatments.

Cellulose fibers can be freed from the cell-wall skeleton via high-shear homogenization, to produce cellulose nanofibers (CNF) that can be used, for example, as the reinforcing phase in composite materials. Nanofiber production from agro-industrial byproducts normally involves harsh chemical-pretreatments and high temperatures to remove noncellulosic polysaccharides (20-70% of dry weight). However, this is expensive for large-scale processing and environmentally damaging. An enzyme-only pretreatment to obtain CNF from agro-industrial byproducts (potato and sugar beet) was developed with targeted commercial enzyme mixtures. It is hypothesized that cellulose can be isolated from the biomass, using enzymes only, due to the low lignin content, facilitating greater liberation of CNF via high-shear homogenization. Comprehensive Microarray Polymer Profiling (CoMPP) measured remaining extractable polysaccharides, showing that the enzyme-pretreatment was more successful at removing noncellulosic polysaccharides than alkaline- or acid-hydrolysis alone. While effective alone, the effect of the enzyme-pretreatment was bolstered via combination with a mild high-pH pretreatment. Dynamic rheology was used to estimate the proportion of CNF in resultant suspensions. Enzyme-pretreated suspensions showed 4-fold and 10-fold increases in the storage modulus for potato and sugar beet, respectively, compared to untreated samples. A greener yet facile method for producing CNF from vegetable waste is presented here.