Lignin from an integrated process consisting of liquid hot water and ethanol organosolv: Physicochemical and antioxidant properties

Abstract

Corncob was successively pretreated by liquid hot water (LHW) and ethanol organosolv (EO) in an integrated process. LHW was performed at 200 °C for 30 min, and EO was performed using uncatalyzed ethanol-water solutions, according to a design of experiments. The effects of the most influential operational variables (ethanol concentration, temperature and time) on yield and chemical composition of the fractions were assessed. Results showed the factor with the greatest effect was ethanol concentration (p < 0.05), leading to a high-purity lignin (86.7%-93.1%) with a total phenolic content of around 25 mg GAE/g. Moreover, the solids recovered from the high ethanol concentration conditions presented the lowest lignin contents (15.4%-17.2%) with good preservation of cellulose (82.5%-88.6% of glucans). The lignin antioxidant capacity showed that all lignin samples presented radical scavenging activity (IC of 0.17 mg/mL and 0.016 mg/mL on DPPH (2,2‑diphenyl‑1‑picrylhydrazyl) and ABTS (2,2'‑azino‑bis(3‑ethylbenzothiazoline‑6‑sulphonic acid) assays, respectively) with values close to the commercial antioxidant BHT. Moreover, the chemical (FTIR) and thermal (DSC and TGA) characterization showed lignins with similar properties that were compared with lignin from direct ethanol organosolv process. Results showed that the integrated process of LHW-EO was the most effective way to obtain lignin with high purity and antioxidant capacity.

Carboxymethyl cellulose-based films: Effect of organosolv lignin incorporation on physicochemical and antioxidant properties

“…The highest RSA values were achieved in the CMC/lignin-based films with high lignin content (100 mg film containing 25 and 50 wt% lignin). The antioxidant activity is explained by the presence of the phenolic hydroxyl groups of lignin (An et al, 2017;Michelin et al, 2018). Maximal RSA of around 90% was achieved with 30 min of reaction in these films.…”

“…Lignin from corncob with 92% purity was obtained after sequential liquid hot water (200 � C, 30 min) and ethanol organosolv (140 � C, 40 min, 60% EtOH) pretreatments according to Michelin et al (2018). Sodium carboxymethylcellulose -CMC (Blanose, 7M65) was obtained from Ashland Inc (Düsseldorf, Germany); Glycerol (99.95%) from Fisher Chemical; Ethanol (99.8%) from Sigma-Aldrich.…”

“…Results showed that soda/AQ lignin and organosolv lignins presented higher antioxidant activity than kraft, DES and hydrotrope lignins. The higher antioxidant activity of the organosolv lignin regarding the other ones has been reported to be related to its lower molecular weight, as well as with its high purity (Arshanitsa et al, 2013;Michelin et al, 2018). Additionally, Guo and co-authors (2019) showed that lignin with a higher content of syringyl units presents a higher antioxidant potential.…”

“…The problem is that these lignins present sulfur chemically bonded to them that is difficult to remove, precluding their use in high value-added applications (W€ ormeyer et al, 2011). Alternatively, organosolv lignin is characterized by its high purity (low inorganic impurities and sulfur-free) and low molecular weight (Mw), making it attractive for applications in bio-based chemicals and materials (Michelin et al, 2018). It presents several properties, such as biodegradability, high thermal stability, antioxidant activity, UV blocking and antimicrobial properties, hydrophobicity, adhesive and other properties (Naseem et al, 2016).…”

Green synthesis of lignin nano- and micro-particles: Physicochemical characterization, bioactive properties and cytotoxicity assessment

“…Organosolv lignin (OL) of high purity (98.73 ± 0.36%) was extracted from corncob through two sequential pretreatments, involving liquid hot water at 200°C for 30 min and organosolv at 140°C for 40 min, using 60% (v/v) ethanol solution, according to Michelin el al. [31]. Ethanol was obtained from Panreac Química SLU (Spain).…”