Rapid determination of lignin content via direct dissolution and ¹H NMR analysis of plant cell walls.

Increasing societal demand for environmental and economic sustainability is placing a renewed focus on the agro-forest industry. This industry plays an essential role in the development of renewable energy and biofuels, especially in light of growing concerns related to energy security and climate change. 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. Although most current bioethanol and biodiesel plants represent first-generation biorefineries, utilizing readily processable bioresources such as sucrose, starches and plant oils, the efficient utilization of all components of biomass to maximize sustainable, economic development is of extreme significance. Among the different biomass sources, the use of lignocellulosics for biofuel production has shown two obvious potential advantages: higher net energy gain and lower production costs. However, the use of lignocellulosics to produce liquid biofuel as a viable alternative to petroleum-based transportation fuels suffers from intrinsic recalcitrance of biomass, owing to the complicated structure of the plant cell walls, which, by their nature, are resistant to breakdown. Thus, a better understanding of plant cell wall structure and its composite materials (cellulose, hemicelluloses, and lignin; see Figure 1) 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 1D). 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, but in other processes such as chemical pulping and forage digestibility also. Therefore, lignin has emerged as one of the leading research fields in bio-