Xylan epitope profiling: an enhanced approach to study organ development-dependent changes in xylan structure, biosynthesis, and deposition in plant cell walls.

BACKGROUND: Xylan is a major hemicellulosic component in the cell walls of higher plants especially in the secondary walls of vascular cells which are playing important roles in physiological processes and overall mechanical strength. Being the second most abundant cell wall polymer after cellulose, xylan is an abundant non-cellulosic carbohydrate constituent of plant biomass. Xylan structures have been demonstrated to contribute to plant biomass recalcitrance during bioenergy applications. A critical understanding of xylan composition, structure, and biosynthesis in developing plant stems will allow an increased understanding of how cell walls are put together in this organ in a basic research, and, in applied research, will improve strategies in xylan engineering to reduce biomass recalcitrance for economically feasible biofuel production. METHODS: We describe an approach to enable the monitoring of xylan epitope structures in cell walls during the stem maturation process in Arabidopsis. The technique integrates glycome profiling, an in vitro immunoanalytical platform, and in situ immunolocalisation to provide comprehensive details on the presence, relative abundances, and dynamics with which diverse xylan epitope structures are integrated to the cell walls throughout the stem maturation process. RESULTS: Our experimental results and the supporting in silico analysis demonstrated that xylan deposition in stems occurs early on in stem development; however, xylan epitope types (representing substituted and unsubstituted regions on xylan backbone made of ß-(1,4)-linked xylose residues) and the strength of their integration into the final wall structure vary during stem maturation. CONCLUSIONS: Our novel approach thus provides a method to comprehensively survey the differences in xylan epitope patterning and deposition occurring in stem development and thereby providing a robust tool for characterising altered xylan integration patterns in cell walls during the stem maturation process in diverse plant cell wall biosynthetic mutants. Our findings also suggest that this approach could rapidly and reliably delineate xylan deposition patterns in the cell walls of plants belonging to diverse phylogenetic classes providing novel insights into the functional roles of xylans in overall growth and development.

Comparison of dietary profile of a rural south Indian population with the current dietary recommendations for prevention of non-communicable diseases (CURES 147).

BACKGROUND & OBJECTIVES: Despite the rising prevalence of non-communicable diseases (NCDs) in rural India, data on the dietary profile of the rural Indian population in relation to the recommendations for prevention of NCDs are scarce. This study was conducted to assess the dietary intake of a rural south Indian population in relation to the current dietary recommendations for the prevention of NCDs. METHODS: The dietary profiles of 6907 adults aged ≥ 20 yr, from a cluster of 42 villages in Kancheepuram district of Tamil Nadu State in southern India, were assessed using a validated food frequency questionnaire. RESULTS: The prevalence of general obesity was 27.4 per cent and that of abdominal obesity, 14.0 per cent among this rural population. The median daily energy intake of the population was 2034 (IQR 543) kcals. More than 3/4 th of the calories (78.1%) were provided by carbohydrates. Refined cereals, mainly polished rice, was the major contributor to total calories. About 45 per cent of the population did not meet WHO recommendation for protein due to low intake of pulses, flesh foods and dairy products and more than half (57.1%) exceeded the limit of salt intake; 99 per cent of the population did not meet WHO recommendations for fruits and vegetables and 100 per cent did not meet the requirement of n-3 poly unsaturated fatty acids. INTERPRETATION & CONCLUSIONS: The dietary profile of this rural south Indian population reflected unhealthy choices, with the high consumption of refined cereals in the form of polished white rice and low intake of protective foods like fruits, vegetables, n-3 poly and monounsaturated fatty acids. This could potentially contribute to the increase in prevalence of NCDs like diabetes, hypertension and cardiovascular diseases in rural areas and calls for appropriate remedial action.

Efficient biomass pretreatment using ionic liquids derived from lignin and hemicellulose.

Ionic liquids (ILs), solvents composed entirely of paired ions, have been used in a variety of process chemistry and renewable energy applications. Imidazolium-based ILs effectively dissolve biomass and represent a remarkable platform for biomass pretreatment. Although efficient, imidazolium cations are expensive and thus limited in their large-scale industrial deployment. To replace imidazolium-based ILs with those derived from renewable sources, we synthesized a series of tertiary amine-based ILs from aromatic aldehydes derived from lignin and hemicellulose, the major by-products of lignocellulosic biofuel production. Compositional analysis of switchgrass pretreated with ILs derived from vanillin, p-anisaldehyde, and furfural confirmed their efficacy. Enzymatic hydrolysis of pretreated switchgrass allowed for direct comparison of sugar yields and lignin removal between biomass-derived ILs and 1-ethyl-3-methylimidazolium acetate. Although the rate of cellulose hydrolysis for switchgrass pretreated with biomass-derived ILs was slightly slower than that of 1-ethyl-3-methylimidazolium acetate, 90-95% glucose and 70-75% xylose yields were obtained for these samples after 72-h incubation. Molecular modeling was used to compare IL solvent parameters with experimentally obtained compositional analysis data. Effective pretreatment of lignocellulose was further investigated by powder X-ray diffraction and glycome profiling of switchgrass cell walls. These studies showed different cellulose structural changes and differences in hemicellulose epitopes between switchgrass pretreatments with the aforementioned ILs. Our concept of deriving ILs from lignocellulosic biomass shows significant potential for the realization of a "closed-loop" process for future lignocellulosic biorefineries and has far-reaching economic impacts for other IL-based process technology currently using ILs synthesized from petroleum sources.