Amphipathic lignin derivatives to accelerate simultaneous saccharification and fermentation of unbleached softwood pulp for bioethanol production

Enhancement and Mechanism of a Lignin Amphoteric Surfactant on the Production of Cellulosic Ethanol from a High-Solid Corncob Residue

A lignin amphoteric surfactant and betaine could enhance the enzymatic hydrolysis of lignocellulose and recover cellulase. The effects of lignosulfonate quaternary ammonium salt (SLQA) and dodecyl dimethyl betaine (BS12) on enzymatic hydrolysis digestibility, ethanol yield, yeast cell viability, and other properties of high-solid enzymatic hydrolysis and fermentation of a corncob residue were studied in this research. The results suggested that SLQA and 1 g/L BS12 effectively improved the ethanol yield through enhancing enzymatic hydrolysis. SLQA had no significant effect on the yeast cell membrane and glucose fermentation. However, 5 g/L BS12 reduced the ethanol yield as a result of the fact that 5 g/L BS12 damaged the yeast cell membrane and inhibited the conversion of glucose to ethanol. Our research also suggested that 1 g/L BS12 enhanced the ethanol yield of corncob residue fermentation, which was attributed to the fact that lignin in the corncob adsorbed BS12 and decreased its concentration in solution to a safe level for the yeast.

Biphasic 2-methyltetrahydrofuran/oxalic acid/water pretreatment to enhance cellulose enzymatic hydrolysis and lignin valorization

A biphasic pretreatment was adopted to disturb the recalcitrant structure of bamboo for further enzymatic hydrolysis and to obtain easily valorized lignin by-product. The biphasic system consisted of biomass-derived chemicals-2-methyltetrahydrofuran and oxalic acid as well as water, and the reactions were conducted at 120-180°C for 20min. The treatment resulted in notable removal of hemicelluloses and lignin. After the pretreatment, the cellulose conversion rate during enzymatic hydrolysis was enhanced by 6.7-fold as compared to the unpretreated raw material. Comprehensive analysis of the lignin product indicated that it exhibited representative structure (such as β-O-4, β-β linkages) as compared to native lignin, contained a very low amount of contaminated sugars (0.67-2.39%), and had a relatively medium molecular weight (Mw 2240-3730g/mol) and good solubility in many organic solvents. This indicated that the lignin showed great potential application in conversion into materials and liquid fuels.

Optimization of simultaneous saccharification and fermentation conditions with amphipathic lignin derivatives for concentrated bioethanol production

Amphipathic lignin derivatives (A-LDs) prepared from the black liquor of soda pulping of Japanese cedar are strong accelerators for bioethanol production under a fed-batch simultaneous enzymatic saccharification and fermentation (SSF) process. To improve the bioethanol production concentration, conditions such as reaction temperature, stirring program, and A-LDs loadings were optimized in both small scale and large scale fed-batch SSF. The fed-batch SSF in the presence of 3.0g/L A-LDs at 38°C gave the maximum ethanol production and a high enzyme recovery rate. Furthermore, a jar-fermenter equipped with a powerful mechanical stirrer was designed for 1.5L-scale fed-batch SSF to achieve rigorous mixing during high substrate loading. Finally, the 1.5L fed-batch SSF with a substrate loading of 30% (w/v) produced a high ethanol concentration of 87.9g/L in the presence of A-LDs under optimized conditions.

Epoxidation and etherification of alkaline lignin to prepare water-soluble derivatives and its performance in improvement of enzymatic hydrolysis efficiency

BACKGROUND

Due to the depletion of fossil resources and their environmental impact, woody biomass has received much attention as an alternative resource. Lignin, as the third most abundant biopolymer from biomass, is now considered as an excellent alternative feedstock for chemicals and materials. The conversion of lignin to the value-added products is a key process to achieve an integrated biorefinery of woody biomass. Among these value-added products, lignin-based derivatives with good surface activity can be applied to enhance the conversion of cellulose into fermentable sugars, which not only decrease the cost of bioethanol production, but also reduce the environmental pollution and green house effect resulting from the burning of fossil resources.

RESULTS

Water-soluble alkaline lignin was synthesized by the reaction between polyethylene glycols (PEG600 and PEG1000) and epoxy lignin. FT-IR and NMR analyses indicated that PEGs were successively introduced into epoxy alkaline lignin using potassium persulfate as a catalyst. Emulsification and surface activity tests indicated that the surface tension of the prepared lignin derivative solution was 43.30 mN/m at the critical micelle concentration (1.03 %). A stable emulsions layer was formed with hexanes and the emulsion particle diameter in the emulsion phase for all products was observed at 10-50 μm. The results of enzymatic hydrolysis indicated that the products derived from PEG1000-grafted lignin resulted in the highest increasing rate of 18.6 % of glucose yield during the enzymatic hydrolysis of hardwood bleached pulp. The results of fermentation experiments suggested that the product had no toxicity for fermentation micro-organisms.

CONCLUSION

Water-soluble alkaline lignin derivatives were prepared through epoxidation and etherification, which are promising feedstocks for detergents, emulsifier, and additive to enhance enzymatic hydrolysis efficiency and ethanol fermentation.