Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695
Performing Department
Forest Biomaterials
Non Technical Summary
To produce high-value co-products from an integrated biorefinery, we propose a research project to selectively separate xylooligosaccharides (xylooligomers, XOS) from lignocellulosic biomass, which can be used as a prebiotic ingredient for functional food. Foods containing prebiotics are a growing segment in the world market due to their benefits to human health. XOS is indigestible by the human metabolism, therefore calorie-free, yet it serves as a fully-digestible carbon source for gut microorganisms. XOS is on the market, although obtained through different means, and it commands a high price ($22~50/kg). Thus, XOS as a co-product generated from biomass will not only promote positive economic impact for a biorefinery, but will also serve as a great contribution to both the food and pharmaceutical industries.We have completed three industrial consortia that have defined practical approaches to produce low cost sugars and found that hydrothermal pretreatment followed by mechanical refining provides the most promising results. In the proposed work, we will develop a resin adsorption system to purify biomass hydrolyzate, crystallize XOS using an evaporative crystallization process, and evaluate the prebiotic potential of obtained XOS. In addition, isolated lignin-carbohydrate complex from resin adsorption will be tested for surfactant application.This proposed project primarily addresses "D: Bioenergy, Natural Resources, and Environment". However, the production and use of XOS will also target other Research Program Areas in the 2014 Farm Bill, including "C: Food Safety, Nutrition, and Health" and "B: Animal Health and Production and Animal Products", as the products from this research can be used for human and animals as functional foods.
Animal Health Component
30%
Research Effort Categories
Basic
70%
Applied
30%
Developmental
0%
Goals / Objectives
To produce high-value co-products from an integrated biorefinery, we propose a research project to selectively separate xylooligosaccharides (xylooligomers, XOS) from biomass, which are a prebiotic ingredient for functional foods. The specific objectives are as follows.Purification of biomass hydrolyzate using resin adsorption.Crystallization of XOS and its characterization.Evaluation of the prebiotic potential of XOS.Application of amphiphilic compounds as a surfactant.
Project Methods
Task 1. Purification of biomass hydrolyzate using resin adsorption First, adsorptive purification of hydrolyzate must be performed with different resin products suggested based on the resins evaluated in our preliminary research. The chemical structure of the utilized resin is known to be the most-significant contributor to the lignin and furan selectivity adsorbed. However, beyond chemical structure, the contribution of factors such as average pore size, pore size distribution and available surface area needs to be elucidated. To achieve this, variants of the resin utilized in our preliminary works will be utilized as an adsorption medium for dissolved lignin and furan removal to study the effects of the resin-specific properties. Beyond the resin itself, several environmental factors must be gauged to better understand the mechanics of selective adsorption, which include hydrolyzate-to-resin ratio, adsorption time, mode of mixing, and the pH of the solution holding suspended resin.Apart from environmental factors, the adsorptivity of the resin after significantly repeated uses must be addressed in order to determine at what point the resin may lose adsorptive capacity. This information is important when considering scale-up of this unit operation. In addition, the minimum resin dosage for maximum adsorption with respect to hydrolyzate volume needs to be determined to reduce financial dependence upon the resin itself. It is expected that this quantity will vary depending upon biomass origin and pretreatment severity. For this reason, multiple biomasses including hardwoods, switchgrass, and sugarcane bagasse will be hydrothermally pretreated at the same severity to produce hydrolyzates and evaluated.Task 2. Crystallization of XOS from hydrolyzate and its characterizationWe will continue to develop a protocol for vacuum crystallization of optimally-purified hydrolyzate obtained by Task 1 and model sugars using a lab-scale rotary evaporator. The hydrolyzate and model sugars will be further concentrated to different concentrations to gauge the effect of XOS concentration upon the obtained XOS crystals. To assist in crystallization, experiments will be performed with and without the presence of a minor quantity of commercial NDOS to provide seeding for crystallization. Additional variables to be tested include crystallization temperature and different commercial NDOS (including commercial XOS) for seeding purposes. The crystalline structure and chemical composition will be analyzed by XRD and HPLC, respectively, to evaluate sample uniformity and remaining impurity.Since the hydrolyzate contains a mixture of sugars with different degrees of polymerization, it will be necessary to better understand the effect of degree of polymerization on crystallization. In addition, gut bacteria are known to be more capable of consuming XOS that are enriched in the low end of molecular weight, mainly xylobiose (X2), xylotriose (X3), and xylotetraose (X4)23. Therefore it is essential to determine the quantity of X2-X4 with respect to the total oligosaccharide distribution. Oligosaccharide distributions will be characterized by IC (ion chromatography) using an electrical conductivity detector.Task 3. Evaluation of the prebiotic potential of XOS The prebiotic potential of the isolated XOS from Task 2 will be evaluated in vitro using both pure culture and fecal inoculum, comparing these results to those obtained using commercial XOS. Firstly, XOS will be cultured with Bifidobacterium spp. in vitro for 24 h. During this time, cell growth, specific growth rate, xylose consumption, and XOS preference will be monitored. The objective is to verify that hydrolysate XOS can support gut associated microbial growth. Later, the prebiotic potential of XOS will be further evaluated using the mixed fecal inocula in batch cultures, to properly simulate the complex gut microbial environmental. During fermentation, the medium's pH, short-chain fatty acid (SCFA) production, and the population change of Bifidobacterium spp., and Lactobacillus spp. will be monitored. We hypothesize that XOS from Task 2 will be fermented in the fecal batch cultures to produce SCFA, which can promote the proliferation of the beneficial bacteria, namely, Bifidobacterium spp. and Lactobacillus spp.In addition to human health benefits, it should be noted that XOS is a highly suitable animal feed; if the isolated XOS does not outperform commercial XOS, then research can be shifted towards understanding how this hydrolyzate fraction can be profitably dropped-in to existing animal feed formulations.Task 4. Evaluation of the amphiphilic compounds for surfactant use Finally, significant work must be performed in order to determine if the obtained lignin-carbohydrate complex amphiphilic surfactants are a suitable replacement for petro-based surfactants. As previously noted, current NMR data has quantified a significant quantity of uronosil esters between lignin and uronic acid moieties in both hardwood and non-wood hydrothermal hydrolyzate lignins. However, in significant difference between the two, a large quantity of phenyl glycoside lignin-carbohydrate complex structures were detected in non-wood hydrolyzate and almost undetectable in hardwood hydrolyzate. For this reason, it will be important to further analyze the differences between differing nonwoods (sugarcane bagasse and switchgrass).Next, the critical micelle concentration of surfactant in water and oil will be determined. It is expected that the lignin-carbohydrate complexes will form differently-oriented micelles depending upon liquid medium. Determination of critical micelle concentration in either medium will inform as to what medium this surfactant would be most effective within. We also hypothesize differences in micellar dimensions based on the different molecular structures of lignin and carbohydrates. To determine this, a light-scattering instrument will be utilized in order to approximate micelle size in order to determine what molecules could potentially be embedded within. Finally, the surfactants will be tested in both water and oil to determine their ability to encapsulate pre-selected hydrophobic or hydrophilic molecules within their inner compartments. Commercially-available water-soluble and oil-soluble agricultural fertilizers will be embedded within the micelle structure. To determine the molecular diffusivity of the micelles, the concentration of free fertilizer will be measured using chromatography with respect to encapsulation time.This is only one of many possible utilizations of the unique lignin-carbohydrate complex structures obtained. We propose to perform an initial evaluation as a surfactant for agricultural industry, where the controlled release of fertilizer into soil is vital to optimal crop production.