Culturing rhodotorula glutinis in fermentation-friendly deep eutectic solvent extraction liquor of lignin for producing microbial lipid.

Currently, deep eutectic solvents (DES) have attracted increasing attention due to their excellent performance in delignification. However, few studies focused on the treatment of DES waste liquid after extraction of lignin. In this work, the fermentation-friendly DES comprised of glycerol, choline chloride (ChCl) and acetic acid (AA) was applied for delignification of lignocellulose. Subsequently, the extraction effects of different DES were investigated, and the DES extraction liquor was used for lipid production. Results shows ChCl made little difference to lipid synthesis, while excessive AA exerted inhibitory effect on the growth of cells. Following pretreatment, the delignification exceeded 63%. When the DES liquid obtained after lignin extraction was used to produce lipid, the delay period was obvious, while the lipid yield and content were unaffected. Not only is the DES prepared in this study effective in delignification of lignocellulose, it is also applicable as raw material to produce lipid.

Non-productive celluase binding onto deep eutectic solvent (DES) extracted lignin from willow and corn stover with inhibitory effects on enzymatic hydrolysis of cellulose.

In this work, deep eutectic solvent (DES) was prepared by mixing choline chloride (ChCl) with lactic acid (LA), and effects of cellulase non-productive binding onto DES-extracted lignin from willow and corn stover on enzymatic hydrolysis of cellulose was investigated. The correlation between hydrolysis yield of cellulose and chemical features of lignin was evaluated, and a potential inhibitory mechanism was proposed. Condensation of lignin was observed during DES treatment, and these condensed aromatic structures had an increased tendency to adsorb enzymes through hydrophobic interactions. As well as hydrophobic interactions mediated by lignin condensation, an increase in phenolic hydroxyl groups resulted in a greater amount of hydrogen bonds between cellulases and lignin that appeared to inhibit enzymatic hydrolysis yields of cellulose (39.96-42.86 % to 31.96-32.68 %). Although large amounts of COOHs were generated, the elevated electrostatic repulsion as a result of ionic groups was insufficient to decrease non-productive adsorption.

Comparison of four types of energy grasses as lignocellulosic feedstock for the production of bio-ethanol.

In order to utilize energy grasses as substrates for production of biofuels and expand the diversity of lignocellulosic feedstocks, this work developed an evaluation system considering 16 kinds of parameters related to the contents of three main compositions (cellulose, hemicellulose and lignin), inhibitors generated from the pretreatment, the extent of enzymatic hydrolysis and microbial fermentation. Giant reed, corn stalks, switch grass, pennisetum and silvergrass were investigated. Comprehensive utilization indexes of giant reed (55.0) and corn stalks (40.6) revealed that giant reed had the potential for producing biofuels but corn stalks, widely used in bio-ethanol and xylitol production, possessed high contents of inhibitors which were harmful to microbial fermentation.

Using a combined hydrolysis factor to balance enzymatic saccharification and the structural characteristics of lignin during pretreatment of Hybrid poplar with a fully recyclable solid acid.

In this study, a new pretreatment strategy for lignocellulosic was developed using a fully recyclable solid acid, Toluenesulfonic acid (p-TsOH). A combined hydrolysis factor (CHF) as a pretreatment severity was used to balance enzymatic saccharification and the structural characteristics of lignin. The results from degradation of carbohydrates, enzymatic hydrolysis of cellulose and characterization of lignin by FT-IR, 31P NMR, GPC, 2D-HSQC NMR indicated that a CHF of approximately 3.90 was the optimal pretreatment severity to facilitate enzymatic saccharification and the potential serviceability of lignin. Then approximately 90% of the xylan was removed to result in a reasonable sugar yield of 76%. Residual lignin showed low molecular weight (Mw, 5783g/mol), narrow polydispersities (Mw/Mn, 1.10) and high content of phenolic hydroxyl groups (3.702mmol/g); it may be a potential feedstock for phenol monomer and polymeric materials production. In short, this process was regarded as a promising approach to achieve an efficient conversion of lignocellulosic biomass to sugar products and lignin-based materials.

The correlation between cellulose allomorphs (I and II) and conversion after removal of hemicellulose and lignin of lignocellulose.

H2SO4, NaOH and H3PO4 were applied to decompose lignocellulose samples (giant reeds, pennisetum and cotton stalks) to investigate the correlation between cellulose allomorphs (cellulose I and II) and conversion of cellulose. The effect of removal of hemicellulose and lignin on the surface morphology, crystallinity index (CrI), cellulose allomorphs (cellulose I and II), and enzymatic hydrolysis under different pretreatments was also studied. CrI caused by H3PO4 pretreatment reached 11.19%, 24.93% and 8.15% for the three samples, respectively. Corn stalk showed highest conversion of cellulose among three samples, irrespective of the pretreatment used. This accounted for the widely use of corn stalk as the renewable crop substrate to synthesize biofuels like ethanol. CrI of cellulose I (CrI-I) negatively affects cellulose conversion but CrI of cellulose II (CrI-II) positively affects cellulose conversion. It contributes to make the strategy to transform cellulose I to cellulose II and enhancing enzymatic hydrolysis of lignocellulose.