Journal
BIOTECHNOLOGY FOR BIOFUELS
Volume 14, Issue 1, Pages -Publisher
BMC
DOI: 10.1186/s13068-021-01993-z
Keywords
Sugarcane bagasse; Xylan; Alkali extraction; Enzymatic hydrolysis; Xylo-oligosaccharides; Thermostable xylanases
Funding
- Lund University
- Novo Nordisk Foundation [NNF18OC0034792]
- University of Tehran (Iran)
Ask authors/readers for more resources
An integrated scheme was developed for successful separation of sugarcane bagasse xylan, lignin, and cellulose. Higher concentration of alkali resulted in xylan with lower degree of substitution, while high pressure conditions released more lignin than xylan. Enzymatic hydrolysis was more efficient using xylan extracted at lower alkaline strength.
Sugarcane processing roughly generates 54 million tonnes sugarcane bagasse (SCB)/year, making SCB an important material for upgrading to value-added molecules. In this study, an integrated scheme was developed for separating xylan, lignin and cellulose, followed by production of xylo-oligosaccharides (XOS) from SCB. Xylan extraction conditions were screened in: (1) single extractions in NaOH (0.25, 0.5, or 1 M), 121 degrees C (1 bar), 30 and 60 min; (2) 3 x repeated extraction cycles in NaOH (1 or 2 M), 121 degrees C (1 bar), 30 and 60 min or (3) pressurized liquid extractions (PLE), 100 bar, at low alkalinity (0-0.1 M NaOH) in the time and temperature range 10-30 min and 50-150 degrees C. Higher concentration of alkali (2 M NaOH) increased the xylan yield and resulted in higher apparent molecular weight of the xylan polymer (212 kDa using 1 and 2 M NaOH, vs 47 kDa using 0.5 M NaOH), but decreased the substituent sugar content. Repeated extraction at 2 M NaOH, 121 degrees C, 60 min solubilized both xylan (85.6% of the SCB xylan), and lignin (84.1% of the lignin), and left cellulose of high purity (95.8%) in the residuals. Solubilized xylan was separated from lignin by precipitation, and a polymer with beta-1,4-linked xylose backbone substituted by arabinose and glucuronic acids was confirmed by FT-IR and monosaccharide analysis. XOS yield in subsequent hydrolysis by endo-xylanases (from glycoside hydrolase family 10 or 11) was dependent on extraction conditions, and was highest using xylan extracted by 0.5 M NaOH, (42.3%, using Xyn10A from Bacillus halodurans), with xylobiose and xylotriose as main products. The present study shows successful separation of SCB xylan, lignin, and cellulose. High concentration of alkali, resulted in xylan with lower degree of substitution (especially reduced arabinosylation), while high pressure (using PLE), released more lignin than xylan. Enzymatic hydrolysis was more efficient using xylan extracted at lower alkaline strength and less efficient using xylan obtained by PLE and 2 M NaOH, which may be a consequence of polymer aggregation, via remaining lignin interactions.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available