(397f) Comparative Leading Pretreatments for Improving Lignin Waste Valorization to Biobased Products

Biorefineries offer a potential solution to the current energy and environmental challenges facing our generation. However, there are still many technical barriers in developing a sustainable biorefinery. Due to the intrinsic recalcitrance of lignocellulosic biomass (LCB), the inherent value of LCB is highly dependent on deconstructing and valorizing lignin polymer in a biorefinery concept, and not just exploiting the more uniform carbohydrates. Lignin is the largest renewable aromatic carbon source and the second most abundant terrestrial polymer after cellulose. Valorizing lignin solid waste to value-added products shows the potential to make a sustainability of biorefineries. Despite these advantages and the significant progress, lignin waste remains as an untapped resource and the application of lignin valorization is relatively unexplored due to the heterogeneity of diverse lignin substrates. We hereby compared the leading pretreatments including sulfuric acid, steam explosion, liquid hot water, AFEX, and alkaline pretreatment for tuning lignin chemistry and improving lignin waste valorization to biobased products. Lignin characterization results showed that the lignin chemistry and reactivity obviously depended on the pretreatment employed. After the delignification of pretreated solid, the lignin stream was used as carbon source for polyhydroxyalkanoates (PHA) production by engineered Pseudomonas putida KT2440. Results showed that multilevel fractionation and utilization process can achieve high-value conversion of lignin for PHA with high yield. Based on the further characterization of lignin form different fractionation streams, the molecular mechanism has been proposed to unveil the improved processibility of lignin from multilevel utilization process. Overall, improving lignin waste valorization to biobased products by employing leading pretreatments provided a unique set of features to deliver a sustainable biorefinery process.