Pretreatment of moso bamboo with p-toluenesulfonic acid for the recovery and depolymerization of hemicellulose

Unlocking full potential of bamboo waster: Efficient co-production of xylooligosaccharides, lignin, and glucose through low-dosage mandelic acid hydrolysis with alkaline processing

Mandelic acid (MA), a natural and environmentally friendly organic acid, demonstrates high selectivity and efficiency in hydrolyzing hemicellulose, making it an excellent candidate for xylooligosaccharides (XOS) production at low acid dosages. Despite its potential, the application of MA for XOS production has not been evaluated. The study first investigated the effectiveness of MA in hydrolyzing hemicellulose in bamboo into XOS. Under optimized conditions (50 mM MA, 180 °C, 45 min), a high XOS yield of 65.9 % was achieved, with a total xylobiose and xylotriose yield of 43.5 %. Subsequent alkaline pretreatment enabled 92.1 % lignin removal from MA-pretreated bamboo. The recovered lignin exhibited a high purity of 95.2 % and retained fundamental structure and functional groups of native lignin. The resulting residue displayed enhanced crystallinity and accessibility, with reduced hydrophobicity and surface area lignin compared to untreated bamboo. At high substrate concentration of 20 %, cellulase hydrolysis resulted in a glucose conversion efficiency of 83.9 %. Overall, this integrated strategy offered an efficient approach for the co-production of valuable XOS, lignin, and glucose from bamboo. The efficient energy utilization and economic viability further highlighted the potential of this method for large-scale industrial applications, making it an attractive option for biomass valorization.

Effect of alkali treatment on enzymatic hydrolysis of p-toluenesulfonic acid pretreated bamboo substrates

The comprehensive separation and utilization of whole components of lignocellulosic materials has received extensive attention in present research. This study focused on the efficacy of alkali treatment for enzymatic saccharification of cellulose based on p-toluenesulfonic acid (p-TsOH) pretreated bamboo substrate. The results showed that the cellulose to glucose conversion yield was 94.69 % under optimized conditions of 0.4 g NaOH/g, 160 °C and 4 h (soaked), which after only 6 h enzymatic hydrolysis time. Alkali lignin recovery was 88.51 %, with potential for conversion to lignin derivatives. The yield of hemicellulose in the pretreated filtrate was 51.85 % after the 4th cycling reuse of p-TsOH. This work has borrowed the advantages of p-TsOH pretreatment of depolymerized hemicellulose from bamboo, combined with a low-priced weak alkali secondary treatment method, which can be effectively applied to the co-production of lignin, xylooligosaccharide, xylose and glucose, and the whole process is green and economically sustainable.

Degradation selectivity for bamboo fiber and parenchyma lignin-carbohydrates complexes (LCC) esters

The degradation of lignin-carbohydrate complex (LCC) esters has been proven to be crucial for the selective separation of lignocellulosic components. This study utilized Raman microspectroscopy to image the preferential degradation of lignin and LCC esters from the bamboo wall during successive NaOH (0.2 to 5.0 % w/w), H2SO4 (1 to 8 % v/v), and NaClO2 (5 to 20 min) treatments. Raman imaging showed that lignin and LCC esters were selectively removed from the middle lamella of fibers and the secondary wall of parenchyma during NaOH and NaClO2 treatments. In contrast, H2SO4 primarily caused the simultaneous removal of lignin and LCC esters from the fiber wall under harsh conditions (8 %), while the middle lamella of parenchyma was less affected, both morphologically and topochemically. Raman spectral analysis indicated that the band intensity at 1605 cm-1 for lignin and at 1173 cm-1 for LCC esters decreased by >87.0 % in the highly lignified parenchyma secondary wall after a 5.0 % NaOH treatment, while the decrease was <67 % in the fiber wall. Interestingly, a strong linear correlation was observed between LCC esters and carbohydrates in the parenchyma (R2 > 0.912). These findings provide important insights into the graded and classified utilization of bamboo resources.

Efficient production of xylobiose and xylotriose from corncob by mixed acids and xylanase hydrolysis

Propionic acid (PA) hydrolysis offers a potential pathway for industrial xylooligosaccharide (XOS) production owing to efficiency and simplicity of the process. However, the cost of XOS production needs to be reduced as PA is expensive. This work proposed a strategy of mixed acids hydrolysis, replacing 20% of PA with formic acid (FA), and combined with xylanase hydrolysis to reduce production costs and increase the production of XOS from corncob. The hydrolysis of corncob using mixed FA and PA in a mass ratio of 2:8 produced 61.8% XOS. Xylanase hydrolysis of corncob residue improved XOS yield to 73.1%. Among them, the X2 + X3 yield was as high as 50.6%. Economic evaluation showed that the combined process reduced the XOS production cost by 10.8% compared to PA hydrolysis. The strategy of using FA instead of 20% PA for hydrolysis and enzymatic hydrolysis, with high XOS and monosaccharide yields from corncob, has potential industrial promise.