Components Analysis of Recycled Alkali Black Liquor Combined with Corn Straw under Ozone Pretreatment

Previous studies showed that the cellulase hydrolysis of corn straw pretreated with circulating alkali black liquor combined with ozone was suppressed. In this paper, the alkali black liquor was sequentially withdrawn for 0–6 times under the optimal pretreatment conditions, and components characterization was analyzed to identify the main factors inhibiting cellulase hydrolysis in recycled alkali black liquor. Through the component analysis, the organic matter and acid precipitation contents increased throughout the cycles. At the fourth cycle, the cellulase hydrolysis rate was decreased significantly, the growth of lignin content in alkali black liquor was slowed down and the total dissolved solid increment was decreased to 8.33mg/mL, 69.52% lower than previous cycle increase. GC-MS results showed that phenols, benzene ring heterocyclic and furans were main degradation products. It indicated that small molecular organics and lignin were inhibitors of cellulase hydrolysis, which accumulated during recycling, reducing alkali utilization and delignification efficiency, resulting in lower enzymatic hydrolysis rate. This study has revealed the components inhibiting the enzymatic hydrolysis of corn straw in recycled alkali black liquor, which is beneficial to the recovery and efficient utilization of recycled alkali black liquor.

A Swollenin From Talaromyces leycettanus JCM12802 Enhances Cellulase Hydrolysis Toward Various Substrates

Swollenins exist within some fungal species and are candidate accessory proteins for the biodegradation of cellulosic substrates. Here, we describe the identification of a swollenin gene, Tlswo, in Talaromyces leycettanus JCM12802. Tlswo was successfully expressed in both Trichoderma reesei and Pichia pastoris. Assay results indicate that TlSWO is capable of releasing reducing sugars from lichenan, barley β-glucan, carboxymethyl cellulose sodium (CMC-Na) and laminarin. The specific activity of TlSWO toward lichenan, barley β-glucan, carboxymethyl cellulose sodium (CMC-Na) and laminarin is 9.0 ± 0.100, 8.9 ± 0.100, 2.3 ± 0.002 and 0.79 ± 0.002 U/mg, respectively. Additionally, TlSWO had disruptive activity on Avicel and a synergistic effect with cellobiohydrolases, increasing the activity on pretreated corn stover by up to 72.2%. The functional diversity of TlSWO broadens its applicability in experimental settings, and indicating that it may be a promising candidate for future industrial applications.

Naganishia cerealis IN1S2.5 oil production from the hydrolysate of NaOH-impregnated and catalyst steam explosion pretreated oil palm empty fruit bunch

NaOH-impregnation with catalyst steam explosion was found to be an efficient pretreatment method for oil palm empty fruit bunch (OPEFB) as a substrate for oil production by Naganishia cerealis IN1S2.5. Cellulase hydrolysis of the pretreated OPEFB yielded glucose at 0.364 g/g. Investigation of N. cerealis IN1S2.5 oil production in the OPEFB hydrolysate revealed a maximum oil yield (2.46 g/L) when the C/P molar ratio of the OPEFB hydrolysate was adjusted to 25.71, supplemented with Ca2+ and Zn2+, and set to pH 4. The N. cerealis IN1S2.5 oil was comprised of oleic (37.6%), palmitic (36.2%), and steric (17.9%) acids, all (w/w), as the major fatty acids. Predicted properties of the produced biodiesel indicated the potential of N. cerealis IN1S2.5 oil as a biodiesel feedstock.

Adsorption Study of Lignin Removal from Recycled Alkali Black Liquor by Adsorption Resins for Improved Cellulase Hydrolysis of Corn Straw

Previous studies showed that aromatic compounds such as lignin, phenols, and furans were main inhibitors of cellulase hydrolysis in recycled alkali black liquor (RBL), which should be removed to improve alkali utilization. In this study, three polymeric resins, XAD-4, XAD-16N, and XAD-7HP, were evaluated for their abilities to remove lignin from alkali black liquor recycled at the third time. Adsorption conditions of adsorbent dose and equilibrium time, isotherms, and kinetics were investigated. Of three tested adsorbents, XAD-16N was the most efficient, which can remove 89.84% of lignin after adsorption at an adsorbent-to-solution ratio of 1:4 for 2.5 h. Pseudo-second-order model was efficient to represent XAD-16N and XAD-7HP adsorption kinetics. Adsorption behavior of XAD-4 on RBL was fitted better to Langmuir model, while XAD-16N and XAD-7HP adsorption were more consistent with Freundlich model. The cellulase hydrolysis rate of corn straw treated with RBL after XAD-16N adsorption combined with ozone was 86.89%, which was only 0.89% lower than that of sodium hydroxide combined with ozone treatment. Structure characterization proved that the damage of XAD-16N adsorbed RBL to corn straw was similar to that of sodium hydroxide. It indicated that adsorption was effective in inhibitor removal from RBL to improve alkali utilization.

Effects of different pretreatment methods on the enzymatic hydrolysis of cassava residue

The enzymatic hydrolysis of cassava residue treated by a hot water (HW) pretreatment, an extreme-low acid (ELA) pretreatment, and an alkaline hydrogen peroxide (AHP) pretreatment was investigated. The results showed that the ELA pretreatment dissolved greater xylan and glucose quantities than the HW pretreatment under the same conditions, and the xylan and glucan contents of the pretreated substrate affected the subsequent cellulase hydrolysis. The conversion to glucose by cellulase hydrolysis reached 81.4% after the HW pretreatment, while the glucose yields under the ELA and AHP pretreatment conditions were 78.3% and 71.0%, respectively. In addition, supplementation with xylanase improved cellulase efficiency. At an equal xylanase dosage, a higher glucose yield (i.e., 91.3%) was achieved for the ELA-pretreated substrates that contained a lower xylan content. Xylanase supplementation in the AHP pretreatment had little effect on the glucose conversion. Finally, X-ray diffraction studies showed that the HW and ELA pretreatments increased the cassava residue crystallinity, while the AHP pretreatment had little effect.

Structural and Physicochemical Characteristics of Rice Bran Dietary Fiber by Cellulase and High-Pressure Homogenization

The present paper aims to study the effect of cellulase hydrolysis and high-pressure homogenization on the structural and physicochemical properties of rice bran dietary fiber (RB-DF). Scanning electron microscopy showed that cellulase treatment led to the formation of a porous structure on RB-DF surface. High-pressure homogenization affected the laminated microstructure of RB-DF, leading to the formation of an irregular and loose surface structure. X-ray diffraction demonstrated that joint processing destroyed the amorphous hemicellulose and cellulose regions, and changed the crystallinity of RB-DF, albeit with a minor impact on the crystalline region of cellulose. Fourier transform infrared spectroscopy indicated that combined processing promoted dissociation of some glycosidic bonds in fiber structure, exposing the hydroxyl groups in cellulose, thus improving their ability to bind water molecules. Thermogravimetric analysis showed a significant decrease in the thermal decomposition temperature of RB-DF (p <0.05) as well as a decrease in thermal stability after combined processing. Cellulase hydrolysis and high-pressure homogenization treatment did not improve their oil holding capacity, but significantly increased water holding capacity, swelling capability, and cation exchange capacity of RB-DF. Thus, enzymatic hydrolysis and high-pressure homogenization treatment can change the structure of RB-DF, exposing a large number of hydrophilic groups and enhancing hydration, obtaining uniform RB-DF particle.