DOI: 10.1002/cssc.201000120 Rapid Determination of Lignin Content via Direct Dissolution and 1 H NMR Analysis of Plant Cell Walls Nan Jiang, [a, b] Yunqiao Pu, [b] and Arthur J. Ragauskas* [a, b] Increasing societal demand for environmental and economic sustainability is placing a renewed focus on the agro-forest in- dustry. This industry plays an essential role in the development of renewable energy and biofuels, especially in light of grow- ing concerns related to energy security and climate change. [1] The economical transformation of differing sources of biomass into biofuels has become a global research theme, directed at displacing nonrenewable petroluem-based resources to reduce long-term carbon dioxide emissions. [2] Although most current bioethanol and biodiesel plants represent first-generation biorefi- neries, utilizing readily processa- ble bioresources such as sucrose, starches and plant oils, [3] the effi- cient utilization of all compo- nents of biomass to maximize sustainable, economic develop- ment is of extreme significance. Among the different biomass sources, the use of lignocellulo- sics for biofuel production has shown two obvious potential ad- vantages: higher net energy gain and lower production costs. [4] However, the use of lignocellulo- sics to produce liquid biofuel as a viable alternative to petrole- um-based transportation fuels suffers from intrinsic recalci- trance of biomass, owing to the complicated structure of the plant cell walls, which, by their nature, are resistant to break- down. [5] Thus, a better under- standing of plant cell wall struc- ture and its composite materials (cellulose, hemicelluloses, and lignin; see Figure 1) [6] has emerged as a crucial research focus. As the “natural glue” for plant cell walls, lignin is the second-most-abundant natural polymer, after cellulose, and is produced by enzyme-mediated radical coupling of the three monolignols (see Figure 1 D). [7] Although lignin can provide a renewable source of phenolic polymers, a high lignin content has proved to be a major obstacle not only in processing of plant biomass to biofuels, [8] but in other processes such as chemical pulping and forage digestibility also. [9] Therefore, lignin has emerged as one of the leading research fields in bio- fuel. With recent advances in lignin engineering via genetic modification of lignin’s biosynthesis, [10] rationally designed bio- energy crops with reduced lignin content to facilitate more ef- ficient degradation of the cell walls has been made possible. However, these programs require assessing a large numbers of “new” plants. For this purpose, precise analytic techniques for efficient lignin content assessment of a large number of sam- ples at a microscale has become a pressing research issue. Many methods based on gravimetric or spectrophotometric analysis have been developed to quantitatively determine Figure 1. A–D) The structures of three major biopolymers of the plant cell walls. E) 1 H NMR spectra of [Hpyr]Cl-d 6 in [D 6 ]DMSO, and F) ball-milled poplar dissolved in 1:2 [Hpyr]Cl-d 6 /[D 6 ]DMSO. [a] Dr. N. Jiang, Prof. A. J. Ragauskas School of Chemistry & Biochemistry Georgia Institute of Technology 901 Atlantic Dr., Atlanta, GA 30332 (USA) Fax: (+ 1) 404 894 4778 E-mail: arthur.ragauskas@chemistry.gatech.edu [b] Dr. N. Jiang, Dr. Y. Pu, Prof. A. J. Ragauskas BioEnergy Center, Institute of Paper Science & Technology Georgia Institute of Technology 500 10th St. NW, Atlanta, GA 30332 (USA) Supporting Information for this article is available on the WWW under http://dx.doi.org/10.1002/cssc.201000120. ChemSusChem 0000, 00, 1 – 5  2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim &1& These are not the final page numbers! ÞÞ