Assessment of antioxidant and antimicrobial properties of lignin from corn stover residue pretreated with low-moisture anhydrous ammonia and enzymatic hydrolysis process

Authors: GUO, MINGMING - University Of Delaware; Jin, Zhonglin; Nghiem, Nhuan; Fan, Xuetong; Qi, Phoebe; JANG, CHAN HO - University Of Delaware; SHAO, LINGXIAO - University Of Delaware; WU, CHANGQING - University Of Delaware

Submitted to: Applied Biochemistry and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2017
Publication Date: 1/1/2018
Citation: Guo, M., Jin, Z.T., Nghiem, N.P., Fan, X., Qi, P.X., Jang, C., Shao, L., Wu, C. 2018. Assessment of antioxidant and antimicrobial properties of lignin from corn stover residue pretreated with low-moisture anhydrous ammonia and enzymatic hydrolysis process. Applied Biochemistry and Biotechnology. 184:350-365.

Interpretive Summary: Production of fuel ethanol and industrial chemicals from renewable biomass feedstocks such as agricultural residues (corn stover) or bioenergy crops (switchgrass) has attracted considerable interest. In this process, the selected feedstock is pretreated with chemicals such as acids or bases to open up the rigid structure of the fibers. The pretreated material then is subjected to hydrolysis by commercial enzyme products to convert the carbohydrate fractions to fermentable sugars, which subsequently are fermented to the desired products. The solid residue obtained at the end of the conversion process, i.e. lignin, normally is burned for energy. However, lignin can be converted to various high-value products, which will offer an economic advantage over heat energy obtained by burning. The main objective of this study was to investigate the antimicrobial and antioxidant activities of the lignin extracts obtained by alkaline extraction from corn stover residue. The extraction process was optimized to achieve the highest lignin yield. It was demonstrated that the lignin extracts exhibited strong antioxidant activities and also displayed antimicrobial activities. Thus the lignin extracts obtained and studied in this work, i.e. a co-product from the biomass-based biorefinery, showed potential for antioxidant and antimicrobial applications such as packaging films and other products.

Technical Abstract: To improve the economic viability of biofuel production from biomass resources, it is increasingly important to develop value-added lignin co-products from this process. The main objective of this study was to investigate the antimicrobial and antioxidant activities of the lignin extracts obtained by alkaline extraction from corn stover residue. The extraction process involved pre-treating the corn stover by low moisture anhydrous ammonia (LMAA), and followed by an enzymatic hydrolysis. Extraction conditions were also optimized to achieve the highest lignin yield. It has been demonstrated that the lignin extracts exhibited strong antioxidant activities by the hydrophilic oxygen radical absorbance capacity (ORAC) assay. Additionally, these extracts also displayed significant antimicrobial activities against Listeria innocua, but had minimal inactivation against the two human norovirus surrogates, namely, murine norovirus and Tulane virus. The optimal extraction conditions using 4% (w/v) sodium hydroxide were determined to be 50 degrees C, 120 min, and 1:8 (w: v), the ratio between corn stover solids to extracting liquid. Using these conditions, nearly 33.92 grams of lignin yield per 100 grams of corn stover residue were obtained. Furthermore, the extracts produced using these conditions also presented the highest antimicrobial and antioxidant activities. Minimal estrogenic impacts were observed for all lignin extracts when tested using the MCF-7 cell proliferation assay, i.e. extracts at 10 ug/mL imposed a similar effect as 17beta-estradiol at 100 fM. Thus the lignin extracts obtained and studied in this work, co-products from the biomass-based biorefinery, showed potential for antioxidant and antimicrobial applications.