Non-productive cellulase adsorption onto lignin has always been deemed to negatively affect the enzymatic hydrolysis of lignocellulosic feedstocks. Therefore, understanding enzyme-lignin interactions is essential for the development of enzyme mixtures, the processes of lignocellulose hydrolysis, and the genetic modification of lignocellulosic biomass and enzymes. In this work, we examined the properties of six lignins from diverse types of lignocellulosic biomass (aspen, pine, corn stover, kenaf, and two Arabidopsis lines, wild-type and SALK mutant of fah1) to determine the mechanism of differences in their adsorption of enzymes. We found that lignin sources affected enzyme adsorption using structural features, such as functional groups and lignin composition. Guaiacyl (G) lignin had a higher adsorption capacity on enzymes than syringyl (S) lignin. The low S/G ratio and high uniform lignin fragment size had good correlations with high adsorption capacity. A higher content of phenolic hydroxyl groups and a lower content of carboxylic acid groups resulted in stronger adsorption affinity for corn stover lignin (CL) than for kenaf lignin (KL) and aspen lignin (AL). The lower amount of aliphatic hydroxyls that reduced hydrophobic interactions could explain the higher adsorption capacity of pine lignin (PL) than CL. Enzyme activity assays, as well as the hydrolysis of Avicel, phosphoric acid-swollen cellulose (PASC), and holocellulose, were performed to study the behaviors of mono-component enzymes that resulted in adsorption. We found that cellobiohydrolase (CBH) and xylanase were adsorbed the most by all lignins, endoglucanase (EG) showed less inhibition, and β-glucosidase (BG) was the least affected by lignins, indicating the important role of carbohydrate-binding module (CBM) in protein adsorption. Lignin sources affect enzyme adsorption using structural features and lignin composition, such as S/G ratio, carboxylic acid, aliphatic hydroxyl, and phenolic hydroxyl. For mono-component enzymes, the adsorption capacity decreased in the order CBH, xylanase > EG > BG. These investigations revealed the difference in lignin properties between diverse biomass and adsorption capacity of enzymes to lignins, and the possible underlying mechanism. The results can also serve as a reference for the genetic modification of lignocellulosic biomass and enzymes.

/pdf/differences-in-the-adsorption-of-enzymes-onto-lignins-from-sou2bczimd.pdf

Differences in the adsorption of enzymes onto lignins from diverse types of lignocellulosic biomass and the underlying mechanism.

Many Penicillium species could produce extracellular enzyme systems with good lignocellulose hydrolysis performance. However, these species and their enzyme systems are still poorly understood and explored due to the lacking of genetic information. Here, we present the genomic and secretomic analyses of Penicillium decumbens that has been used in industrial production of lignocellulolytic enzymes in China for more than fifteen years. Comparative genomics analysis with the phylogenetically most similar species Penicillium chrysogenum revealed that P. decumbens has evolved with more genes involved in plant cell wall degradation, but fewer genes in cellular metabolism and regulation. Compared with the widely used cellulase producer Trichoderma reesei, P. decumbens has a lignocellulolytic enzyme system with more diverse components, particularly for cellulose binding domain-containing proteins and hemicellulases. Further, proteomic analysis of secretomes revealed that P. decumbens produced significantly more lignocellulolytic enzymes in the medium with cellulose-wheat bran as the carbon source than with glucose. The results expand our knowledge on the genetic information of lignocellulolytic enzyme systems in Penicillium species, and will facilitate rational strain improvement for the production of highly efficient enzyme systems used in lignocellulose utilization from Penicillium species.

/pdf/genomic-and-secretomic-analyses-reveal-unique-features-of-3i14g4ifd6.pdf

Genomic and secretomic analyses reveal unique features of the lignocellulolytic enzyme system of Penicillium decumbens.

Development, characterization and application of intelligent/active packaging of chitosan/chitin nanofibers films containing eggplant anthocyanins

This review focuses on cellulases from Penicillium species with emphasis on cellulose biodegradation; the most laborious step in the production of biofuels from lignocellulosic biomass. Extracellular multienzyme systems secreted by various Penicillium species proved to be highly efficient destroyers of cellulose in comparison with competitive producers of cellulases. Data on cellulase production levels by Penicillia, enzyme induction and regulation, composition of the secreted multienzyme systems, examples of their application for hydrolysis of lignocellulosic residues, as well as reasons for their high saccharification performance, are discussed. Analysis of the data shows that Penicillium cellulases are very promising candidates for production of the second-generation biofuels; however, some issues should be resolved in order for them to become cost competitive to enzymes produced by other microorganisms (in particular, to those from Trichoderma reesei).

Cellulases from Penicillium species for producing fuels from biomass

Non-specific binding of cellulases to lignin has been implicated as a major factor in the loss of cellulase activity during biomass conversion to sugars. It is believed that this binding may strongly impact process economics through loss of enzyme activities during hydrolysis and enzyme recycling scenarios. The current model suggests glycoside hydrolase activities are lost though non-specific/non-productive binding of carbohydrate-binding domains to lignin, limiting catalytic site access to the carbohydrate components of the cell wall. In this study, we have compared component enzyme affinities of a commercial Trichoderma reesei cellulase formulation, Cellic CTec2, towards extracted corn stover lignin using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and p-nitrophenyl substrate activities to monitor component binding, activity loss, and total protein binding. Protein binding was strongly affected by pH and ionic strength. β-d-glucosidases and xylanases, which do not have carbohydrate-binding modules (CBMs) and are basic proteins, demonstrated the strongest binding at low ionic strength, suggesting that CBMs are not the dominant factor in enzyme adsorption to lignin. Despite strong adsorption to insoluble lignin, β-d-glucosidase and xylanase activities remained high, with process yields decreasing only 4–15 % depending on lignin concentration. We propose that specific enzyme adsorption to lignin from a mixture of biomass-hydrolyzing enzymes is a competitive affinity where β-d-glucosidases and xylanases can displace CBM interactions with lignin. Process parameters, such as temperature, pH, and salt concentration influence the individual enzymes’ affinity for lignin, and both hydrophobic and electrostatic interactions are responsible for this binding phenomenon. Moreover, our results suggest that concern regarding loss of critical cell wall degrading enzymes to lignin adsorption may be unwarranted when complex enzyme mixtures are used to digest biomass.

/pdf/new-perspective-on-glycoside-hydrolase-binding-to-lignin-1j8d7457ht.pdf

New perspective on glycoside hydrolase binding to lignin from pretreated corn stover

Development and characterization of chitosan/guar gum active packaging containing walnut green husk extract and its application on fresh-cut apple preservation.

This work, curcumin/β-cyclodextrin inclusion complex (CUR/β-CD IC) nanoparticles were successfully synthesized via flexible and efficient nanoprecipitation using absolute ethanol as precipitant. At the 1:2 and 1:1 M ratios of CUR/β-CD nanoparticles, the encapsulation efficiency reached more than 70%, and particle size was ∼200 nm. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) results validated the construction of CUR/β-CD nanoparticles. FT-IR results indicated that CUR remained in β-CD cavity, and the IC molecules aggregated to form nanoparticles via intermolecular hydrogen bonding. XRD results displayed the formation of new solid crystal phases in CUR/β-CD IC nanoparticles. As-synthesized CUR/β-CD IC nanoparticles exhibited excellent physicochemical stability compared to free CUR. Encapsulation of CUR within nanoparticles also improved its bioavailability. Therefore, nanoprecipitation is a promising approach to synthesize CD-based nanoparticles for delivery of CUR or other phytochemicals with enhanced stability and bioavailability. 

Preparation and characterization of curcumin/β-cyclodextrin nanoparticles by nanoprecipitation to improve the stability and bioavailability of curcumin

Encapsulation of catechin into nano-cyclodextrin-metal-organic frameworks: Preparation, characterization, and evaluation of storage stability and bioavailability.

Development of active packaging with chitosan, guar gum and watermelon rind extract: Characterization, application and performance improvement mechanism.

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