Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption

A new colorimetric method for determining the surface-accessible acidic lignin hydroxyl groups in lignocellulose solid fractions was developed. The method is based on selective adsorption of Azure B, a basic dye, onto acidic hydroxyl groups of lignin. Selectivity of adsorption of Azure B on lignin was demonstrated using lignin and cellulose materials as adsorbents. Adsorption isotherms of Azure B on wheat straw (WS), sugarcane bagasse (SGB), oat husk, and isolated lignin materials were determined. The maximum adsorption capacities predicted by the Langmuir isotherms were used to calculate the amounts of surface-accessible acidic hydroxyl groups. WS contained 1.7-times more acidic hydroxyls (0.21 mmol/g) and higher surface area of lignin (84 m2/g) than SGB or oat husk materials. Equations for determining the amount of surface-accessible acidic hydroxyls in solid fractions of the three plant materials by a single point measurement were developed. A method for high-throughput characterization of lignocellulosic materials is now available

Trans-10, cis-12 Conjugated Linoleic Acid Induces Lipid Degradation and Attenuates Fatty Acid Desaturation in Yeast Saccharomyces cerevisiae

Yeast has been successfully utilized as a model organism to study the antilipogenic mechanism of the trans-10, cis-12 isomer of conjugated linoleic acid (CLA). The isomer lowered triacylglycerol content of yeast if supplemented in the cultivation medium. Also monounsaturated to saturated fatty acid ratio in yeast lipids was reduced in the CLA treated cells. In this study, the metabolic conditions in terms of lipid reduction were examined to clarify the antilipogenic mechanism of CLA in yeast. Triacylglycerol accumulation and degradation were examined and desaturation of trans-vaccenic acid to cis-9, trans-11 CLA was measured in the trans-10, cis-12 CLA treated cells. The study confirmed that triacylglycerol accumulation was not prevented in the trans-10, cis-12 CLA treated cells evidenced by the intensive co-accumulation of oleic acid. In the trans-10, cis-12CLA treated culture the triacylglycerol content started to decrease and cellular biomass increase in the stationary phase after the cells had shifted their metabolism from fermentation to respiratory metabolism. This indicated that yeast used the liberated fatty acids for β-oxidation. The lowered capacity to desaturate the trans-vaccenic acid to cis-9, trans-11 CLA pointed out that also desaturase inhibition hasan important role in the antilipogenic mechanism of the trans-10, cis-12 CLA in yeast.Peer reviewe

Reduction of surface area of lignin improves enzymatic hydrolysis of cellulose from hydrothermally pretreated wheat straw

Enzymatic hydrolysis of cellulose after pretreatment of wheat straw (WS) was investigated for the first time in relation to lignin surface area (SA). Lignin SA in solid residues from WS autohydrolysis (AH) and successive NH3 (aq) extraction was determined using cationic dye adsorption. AH at increasing severity decreased up to 45% and 53% of WS lignin SA and specific surface area (SSA), respectively. Cellulose-to-glucose conversion from AH solid fractions from 24 h reaction with 15 FPU g−1 cellulase activity increased linearly from 31% to 91% with decreasing lignin SA. When AH solid fractions were extracted with NH3 (aq), both lignin SA and SSA increased in the corresponding solid residues, SSA up to 92%. As a consequence, cellulose-to-glucose conversion decreased in spite of the lower proportion of lignin in the solid residues after the NH3 (aq) extraction. Up to 85% sugar yield was obtained from the single-stage AH process but when combined with NH3 (aq) extraction the two-stage process yielded at most 71% of the original straw sugars. These results show that, independent of the lignin content, reduction of surface area of lignin improves the enzymatic hydrolysis process.Peer reviewe

Fractionation process for the protective isolation of ergosterol and trehalose from microbial biomass

A new process is described for the two phase extraction of ergosterol and trehalose from microbial biomass. Baker's yeast was used as a model organism to develop the method, which was then applied for extracting 13 oleaginous microbes. Major findings of the study were that the ergosterol content was not dependent on intracellular oil content and that 1-butanol and alkaline pH were needed to protect ergosterol. Saponification for 3-4. h at 85-100. °C followed by extraction of the reaction mixture with toluene gave the maximal ergosterol yield. Trehalose was stable at this temperature and remained in water solution, but the maximal yield was obtained after a shorter reaction time at lower alkalinity. Although trehalose alone is stable at alkaline pH, extraction yields of trehalose from yeast decreased with increasing alkalinity. This finding led us to propose a two-step process in which trehalose is separated in the first step and ergosterol in the second. The possibility to apply this method to fractionate oleaginous microbes in process scale is discussed from technical viewpoints.Peer reviewe

Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption

Abstract A new colorimetric method for determining the surface-accessible acidic lignin hydroxyl groups in lignocellulose solid fractions was developed. The method is based on selective adsorption of Azure B, a basic dye, onto acidic hydroxyl groups of lignin. Selectivity of adsorption of Azure B on lignin was demonstrated using lignin and cellulose materials as adsorbents. Adsorption isotherms of Azure B on wheat straw (WS), sugarcane bagasse (SGB), oat husk, and isolated lignin materials were determined. The maximum adsorption capacities predicted by the Langmuir isotherms were used to calculate the amounts of surface-accessible acidic hydroxyl groups. WS contained 1.7-times more acidic hydroxyls (0.21 mmol/g) and higher surface area of lignin (84 m 2 /g) than SGB or oat husk materials. Equations for determining the amount of surface-accessible acidic hydroxyls in solid fractions of the three plant materials by a single point measurement were developed. A method for high-throughput characterization of lignocellulosic materials is now available.

Autohydrolysis and aqueous ammonia extraction of wheat straw: effect of treatment severity on yield and structure of hemicellulose and lignin

The objective of this study was to elucidate the impact of autohydrolysis severity on the yield and structure of wheat straw hemicellulose and lignin. The autohydrolysis treatments were carried out at maximum temperatures between 170 °C and 200 °C. The autohydrolysis liquors were separated and the solids were successively extracted with aqueous ammonia either in moderate or high intensity extraction conditions to dissolve lignin for analysis. Increasing autohydrolysis severity decreased the molar mass of the aqueous ammonia extracts from 5450 g mol−1 to 1810 g mol−1, and carbohydrate content from 6% to 0.1%. The optimum autohydrolysis severity (log R0 = 3.81) for xylan recovery released mainly oligomeric arabinoxylans at 66% xylan recovery yield. Drastic degradation of pentoses occurred beyond the optimum severity. As an indication of accumulation of “pseudo-lignin” during autohydrolysis, decreasing relative aromaticity in the aqueous ammonia extracts as a function of autohydrolysis severity was shown. The finding was confirmed by quantitative analysis of the cupric oxide oxidation products of lignin suggesting up to 55% decrease in the relative amount of native lignin at the highest severity. These results show the importance of distinguishing between lignin and “pseudo-lignin” in fractions obtained from lignocellulosic materials subjected to acidic pretreatment.Peer reviewe

Effect of catalysts and pH on lignin in partial wet oxidation of wood and straw black liquors

Peer reviewe