Cellulose Degradation Products Research Articles

Solubility, complexation and thermodynamics of the Tc(IV)–isosaccharinic acid system: Trends in the M(IV) series

Isosaccharinic acid (HISA, or ISA in its deprotonated form) is the main degradation product of cellulose under alkaline conditions. It can form strong complexes with radionuclides and other toxic metal ions, eventually enhancing their mobility in the context of nuclear waste repositories and other environmental systems. 99Tc is a redox-sensitive, long-lived fission product produced in high yield in nuclear reactors. The solubility of 99Tc(IV) was investigated in 0.5 M NaCl‒NaISA‒NaOH solutions with 6 ≤ pHm ≤ 12.5 and 10−6 M ≤ [ISA] ≤ 0.2 M. Complete chemical and thermodynamic models were derived on the basis of solubility data, (pe + pHm) measurements, redox speciation, and solid phase characterization. These models include the previously unreported aqueous complexes TcO(OH)(ISA)2‒ and TcO(OH)2(ISA)22−. In spite of the small size and high polarizability of the Tc4+ metal ion, the Tc(IV)-ISA complexes described in this work are significantly weaker than other ISA complexes formed with larger M4+ metal ions, i.e., Zr, Pu and U. This unexpected behavior can be possibly explained by the strong hydrolysis of Tc(IV) and corresponding stabilization of the TcO2+ moiety, which does not occur for other M(IV) systems. Thermodynamic data derived in this work can be implemented in geochemical calculations of relevance in the context of nuclear waste disposal and other environmental applications.

Reconstruction and analysis of the gene regulatory network for cell wall function in Arabidopsis thaliana L. leaves in response to water deficit.

The plant cell wall represents the outer compartment of the plant cell, which provides a physical barrier and triggers signaling cascades under the influence of biotic and abiotic stressors. Drought is a factor that negatively affects both plant growth and development. Cell wall proteins (CWP) play an important role in the plant response to water deficit. The adaptation mechanisms of the cell wall to water loss are of interest for identifying important genetic factors determining plant drought resistance and provide valuable information on biomarkers for further selection aimed at increasing the yield of crop plants. Using ANDSystem, a gene network describing the regulation of CWPs under water restriction conditions was reconstructed. The analysis of the gene network and the transcriptome data analysis allowed prioritizing transcription factors (TF) based on their enrichment of differentially expressed genes regulated by them. As a result, scores were calculated, acting as indicators of the association of TFs with water deficit. On the basis of the score values, eight most significant TFs were selected. The highest priority was given to the TF GBF3. CWPs were prioritized according to the criterion of summing up the scores of transcription factors regulating these genes. Among the most prioritized CWPs were the AT5G03350 gene encoding a lectin-like protein, AT4G20860 encoding BBE-like 22 required for the oxidation of cellulose degradation products, and AT4G37800 encoding xyloglucan endotransglucosylase/ hydrolase 7. Overall, the implemented algorithm could be used for prediction of regulatory interactions between transcription factors and target genes encoding cell wall proteins in plants.

Paper Waste Hydrolysis with Stepwise Sulfuric Acid Catalyst

The need for paper results in a lot of paper waste. Paper waste, which is lignocellulosic, can be hydrolyzed using an acid catalyst to produce various cellulose degradation products. In this study, the effect of the sulfuric acid catalyst addition method on the waste paper hydrolysis process was investigated. The addition of the catalyst was carried out in three types. The Type-1 method was sulfuric acid addition in the 0th minute. The Type-2 method was sulfuric acid addition in the 0th and 30th minutes. The Type-3 method was sulfuric acid addition every 10 minutes. The results showed that the lowest residual mass of waste paper hydrolyzed was produced using the Type-3 method. This showed that the Type-3 method, sulfuric acid addition every 10 minutes, had an effect on the residual mass of the hydrolyzed sample. The Type-3 method was the most effective type of sulfuric acid catalyst addition compared to other types. On the other hand, variations in the concentration of the sulfuric acid catalyst affect the residual mass of the waste paper hydrolyzed sample, where higher sulfuric acid concentration will lower residual mass. The catalyst concentration of 2% sulfuric acid with The Type-3 addition method resulted in the highest conversion which was 38.27%.

Investigating the effect of pore water composition and isosaccharinic acid (ISA) on sorption of Pu to a CEM III/C-based mortar

In the frame of the safe disposal of short-lived low and intermediate level nuclear waste (SL-ILW), ONDRAF/NIRAS (Belgium) has submitted a license application for the exploitation of a near surface facility in Dessel (Belgium). A significant part of the waste intended for the surface repository is Pu-contaminated and has been conditioned by means of CEM III/C based mortar, produced in the CILVA-installation at the Belgoprocess site in Dessel. To establish more accurate data on sorption of Pu to the CILVA mortar, an experimental test set-up was designed in order to screen which factors were likely to affect Pu sorption to the mortar. The different factors of the design were variables related to the pore water composition of the mortar on the one hand (concentrations of Ca2+, Cl−, SO42−, S2−, K+ and OH− (pH)), and variables characteristic for batch sorption experiments on the other hand ([Pu], solid-to-liquid ratio and equilibration time). The results of this screening indicate that over the tested variables, only the concentration of Ca2+ in the synthetic pore water affects Pu sorption to the CILVA matrix to a significant extent. Additionally, from literature it is expected that the presence of isosaccharinic acid (ISA), a cellulose degradation product, would affect Pu sorption, with increasing concentrations of ISA frequently correlated with decreased sorption. To address the nature and extent of the impact of both [Ca2+] and [ISA] and their combined effect on sorption of Pu to the mortar, an experimental set-up for surface response measurement (SRM) was designed. A Central Composite Design (CCD) in two factors was selected for the SRM, with three test points and a four point repetition of the centre point. The execution of this experimental set-up and the resulting responses, allowed for the development of a polynomial model to predict the average response of Pu sorption (expressed as Rd) as a function of [ISA] and of [Ca2+]. In addition, the [Ca2+] in solution in equilibrium with the mortar could be assessed from the established dataset, which allowed to predict Pu sorption as a function of [ISA] at the intrinsic [Ca2+] in the mortar’s pore water.

Characterization of the degradation products of lignocellulosic biomass by using tandem mass spectrometry experiments, model compounds, and quantum chemical calculations.

Biomass-derived degraded lignin and cellulose serve as possible alternatives to fossil fuels for energy and chemical resources. Fast pyrolysis of lignocellulosic biomass generates bio-oil that needs further refinement. However, as pyrolysis causes massive degradation to lignin and cellulose, this process produces very complex mixtures. The same applies to degradation methods other than fast pyrolysis. The ability to identify the degradation products of lignocellulosic biomass is of great importance to be able to optimize methodologies for the conversion of these mixtures to transportation fuels and valuable chemicals. Studies utilizing tandem mass spectrometry have provided invaluable, molecular-level information regarding the identities of compounds in degraded biomass. This review focuses on the molecular-level characterization of fast pyrolysis and other degradation products of lignin and cellulose via tandem mass spectrometry based on collision-activated dissociation (CAD). Many studies discussed here used model compounds to better understand both the ionization chemistry of the degradation products of lignin and cellulose and their ions' CAD reactions in mass spectrometers to develop methods for the structural characterization of the degradation products of lignocellulosic biomass. Further, model compound studies were also carried out to delineate the mechanisms of the fast pyrolysis reactions of lignocellulosic biomass. The above knowledge was used to assign likely structures to many degradation products of lignocellulosic biomass.

Simulatenous evaluation of composting experiments and metagenome analyses to illuminate the effect of Streptomyces spp. on organic matter degradation.

The effect of Streptomyces spp. on organic matter degradation was investigated in the present study. Streptomyces spp. isolated from compost systems were eliminated based on the results of cellulose, starch, xylan degradation tests, morphological inspection, and 16S rRNA analysis. The eliminated strains were re-given to compost systems to determine their effect on organic matter degradation and maturation. Sample analyses indicated that 15days of composting had been adequate to maintain maturation. The amounts of strains added to the system were high enough to create a detectable change such as inhibition of other microbiota members. Results also indicated a variant change in organic matter degradation due to the added strain. The difference in organic matter degradation between strains depended partially on the segregation of secondary metabolites. On the other hand, strains also inhibited each other in the case of their binary and triple utilization in compost. Another explanation for variant activity was provided based on the enzymatic activity of the strains validated by metagenomic counts evaluation. Metagenome count numbers revealed the tendency of compost microbiota toward degradation products of cellulose. Findings obtained from composting experiments and metagenome analyses indicated the presence of a different degradation route based on xylan activity. Results also implied a decrease in competition between the dominant strain and microbiota members in the case of sequential xylan and cellulose degradation. Meticulous evaluation of results obtained from metagenome analysis also provided some insights on certain conditions regarding the progress of composting along with storage conditions of manure before use.

Cellulose degradation products and high ionic strength enhance the retardation of strontium in hydrated cement paste

The present concept for the disposal of some low- and all intermediate-level radioactive waste in the United Kingdom involves grouting with cement in steel drums and placement in a geological facility. The vaults would then be backfilled with low strength, high porosity cement-based materials designed to promote a pervasive, alkaline environment in which many of the radioactive species present are sparingly soluble. This work investigates the interaction of strontium with such a backfill under both diffusive and advective conditions given the potential significance of the fission product 90Sr. An important characteristic of the United Kingdom waste inventory is the abundance of organic compounds, including cellulosic materials; consequently, the experiments were repeated with products of alkaline cellulose degradation. Additional experiments were performed at high ionic strength simulating anticipated changes in the salinity of the groundwater. The effective diffusivity (De) of strontium in the absence of the organic compounds ranged between 5.5 × 10−11 and 8.5 × 10−11 m2 s−1, with a distribution coefficient (Rd) of between 2.8 × 10−3 and 3.1 × 10−3 m3 kg−1. The presence of organic compounds and/or an increase of ionic strength enhanced the retardation of strontium. The results indicate that the retention of strontium by hydrated cement paste occurs via a reversible ion exchange mechanism rather than mineralisation and is promoted by decalcification of the calcium silicate hydrate phases.

The Release of Non-Extractable Ferulic Acid from Cereal By-Products by Enzyme-Assisted Hydrolysis for Possible Utilization in Green Synthesis of Silver Nanoparticles.

The present work was undertaken to elucidate the potential contribution of biosynthetically produced ferulic acid (FA) via enzymatic hydrolysis (EH) of rye bran (RB) to the formation of silver nanoparticles (AgNPs) during green synthesis. An analytical approach accomplished by multiple reaction monitoring (MRM) using triple quadrupole mass selective detection (HPLC-ESI-TQ-MS/MS) of the obtained hydrolysate revealed a relative abundance of two isomeric forms of FA, i.e., trans-FA (t-FA) and trans-iso-FA (t-iso-FA). Further analysis utilizing high-performance liquid chromatography with refractive index (HPLC-RID) detection confirmed the effectiveness of RB EH, indicating the presence of cellulose and hemicellulose degradation products in the hydrolysate, i.e., xylose, arabinose, and glucose. The purification process by solid-phase extraction with styrene-divinylbenzene-based reversed-phase sorbent ensured up to 116.02 and 126.21 mg g−1 of t-FA and t-iso-FA in the final eluate fraction, respectively. In the green synthesis of AgNPs using synthetic t-FA, the formation of NPs with an average size of 56.8 nm was confirmed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. The inclusion of polyvinylpyrrolidone (PVP-40) in the composition of NPs during synthesis favorably affected the morphological features, i.e., the size and shape of AgNPs, in which as big as 22.4 nm NPs were engineered. Meanwhile, nearly homogeneous round-shaped AgNPs with an average size of 16.5 nm were engineered using biosynthetically produced a mixture of t-FA and t-iso-FA and PVP-40 as a capping agent. The antimicrobial activity of AgNPs against Gram-positive and Gram-negative bacteria, including Pseudomonas aeruginosa, E. coli, Enterococcus faecalis, Bacillus subtilis, and Staphylococcus aureus was confirmed by the disk diffusion method and additionally supported by values of minimum inhibitory (MIC) and bactericidal (MBC) concentrations. Given the need to reduce problems of environmental pollution with cereal processing by-products, this study demonstrated a technological solution of RB rational use in the sustainable production of AgNPs during green synthesis. The AgNPs can be considered as active pharmaceutical ingredients (APIs) to be used for developing new antimicrobial agents and modifying therapies in treating multi-drug resistant (MDR) pathogens.

Effects of the presence of isosaccharinate on nickel adsorption by calcium silicate hydrate (CSH) gels: Experimental analysis and surface complexation modelling

The presence of organics may enhance contaminant mobility; thus, the evaluation of radionuclide-organic-cement interactions is a topic of particular interest for the safety assessment of low-intermediate level radioactive waste (LILRW) disposals. The objective of this work is to analyse nickel adsorption on the most abundant phases of hydrated cement paste, calcium silicate hydrate (CSH), in the presence of isosaccharinic acid (Isa), the principal degradation product of cellulose under alkaline conditions. Two different CSHs were studied (Ca/Si ratios of 0.8 and 1.4) to cover a range of chemical conditions representative of different cement degradation stages. To gather information on the interactions in the ternary Ni/Isa/CSH system, batch sorption tests, electrophoretic measurements, and spectroscopic analyses (FT-IR) were combined. The presence of Isa at a concentration up to 1·10−2 M slightly decreased the surface charge (−10 mV) of the two CSH phases analysed, and moderately affected Ni adsorption, causing a diminution of Kd(Ni) by less than 1 order of magnitude. To interpret the experimental dataset, surface complexation modelling was successfully used in this system for the first time. The modelling was based on a double layer approach, which accounts for the properties of the binary Ni/CSH system and includes the formation of Ni-Isa aqueous complexes as well as Isa adsorption on the CSH, under the specific chemical conditions generated by the solids.

Effect of lignocellulosic components on the hydrothermal carbonization reaction pathway and product properties of protein

Blending lignocellulosic biomass with sewage sludge can further improve the fuel performance of hydrochar. Investigating the effects of different lignocellulosic components on protein hydrothermal carbonization (HTC) reaction pathways and product properties can provide insights into ways to screen lignocellulosic biomass. In this study, cellulose, hemicellulose, and lignin were selected for co-HTC with protein in different mass ratios (1:2 and 2:1). Results showed that the dehydration and decarboxylation reactions were strong when protein–hemicellulose co-HTC in a mass ratio of 2:1, and the O/C and H/C atomic ratios of the hydrochar decreased to 0.14 and 1.19, respectively. As the blending ratio of lignocellulosic components increased, the interaction gradually reached saturation, and the synergistic effect on the properties of mixture hydrochar decreased. Moreover, the functional group characteristics of the mixture hydrochar tended to resemble the chemical structures of lignocellulosic components. The Maillard and Mannich reactions between lignocellulosic components and proteins during co-HTC resulted in the re-solidification of N-containing compounds in the liquid-phase products. The degradation products of protein and (hemi)cellulose (glucose and furfural) were polymerized into char by the Maillard reaction. However, water-soluble N-containing compounds were immobilized into char through adsorption or reaction with lignin O-containing functional groups.

Parallel proteomic and phosphoproteomic analyses reveal cellobiose‐dependent regulation of lignocellulase secretion in the filamentous fungus Neurospora crassa

AbstractHigh cost of lignocellulases restricts the commercialization of biofuel and bio‐product production from lignocellulosic biomass. Constitutively expressed lignocellulases are considered to degrade cellulose to release small amount of soluble cellodextrins such as cellobiose for further large‐scale production of lignocellulases; however, the underlying mechanism remains to be elucidated. Here, a triple β‐glucosidase mutant of the model fungus Neurospora crassa, which prevents rapid turnover of cellobiose and thus allows the disaccharide to induce lignocellulases, was applied to perform parallel analyses of proteome and phosphoproteome changes in response to cellobiose and Avicel cellulose. The results revealed shared proteome and phosphoproteome responses to cellobiose and Avicel, corroborating the idea that cellobiose mediates the regulation of lignocellulase expression and secretion. The results further suggest that this regulation is achieved at multiple levels, including epigenetic, transcription, post‐transcription, translation, and post‐translation. Proteome profiling revealed that the proteins upregulated by cellobiose and Avicel were over‐represented in cellulose degradation and degradation product transport pathways. Phosphoproteome profiling revealed that the proteins differentially phosphorylated by cellobiose and Avicel were over‐represented by the pathways such as transcriptional control, protein processing and export, cell wall biogenesis, and cellular signaling. Deletion mutation analysis further suggests that the ER chaperon protein Hsp70‐6, the translocation complex subunit Sec66/Sec71, and the signal peptidase subunit Spc2 are involved in lignocellulase secretion, particularly translocation across the endoplasmic reticulum. Altogether, the results offer a new insight into how cellobiose mediates the regulation of lignocellulase expression and secretion, providing a potential strategy for the strain engineering to improve lignocellulase production.

Investigation on Formation Mechanisms of Methanol During Cellulose Insulation Aging Based on Molecular Dynamics Simulation

In recent years, methanol has been proposed as a chemical indicator to assess the aging condition of cellulose insulation in oil-immersed power transformers. However, the formation mechanisms of methanol during cellulose degradation are not clear enough. In this paper, such formation mechanisms were studied using molecular dynamics simulation. Three main formation pathways of methanol were found and discussed. Analysis of the Mayer bonds of cellulose revealed that each atom of cellulose contributes differently to methanol formation. The methylol groups on the 5-carbon atom of the 1-pyran ring and 4-pyran ring of cellulose are more readily detached to form methanol molecules. In addition, changes in the amount of methanol molecule with simulation time were investigated. The results indicated that the separate existence of initial moisture and oxygen has no significant effect on the formation of methanol, while the co-existence of initial moisture and initial oxygen catalyzes the conversion of cellulose degradation products to methanol. The findings reported in this paper can provide a valuable theoretical basis for further studies on methanol as an indicator to evaluate the residual life of cellulose insulation.

Cellulolytic bacterium characterization and genome functional analysis: An attempt to lay the foundation for waste management

Lignocellulosic waste has offered a cost-effective and food security-wise substrate for the generation of biofuels and value-added products. Here, whole-genome sequencing and comparative genomic analyses were performed for Serratia sp. AXJ-M. The results showed that strain AXJ-M contained a high proportion of strain-specific genes related to carbohydrate metabolism. Furthermore, the genetic basis of strain AXJ-M for efficient degradation of cellulose was identified. Cellulase activity tests revealed strong cellulose degradation ability and cellulase activities in strain AXJ-M. mRNA expression indicated that GH1, GH3 and GH8 might determine the strain’s cellulose degradation ability. The SWISS-MODEL and Ramachandran Plot were used to predict and evaluate the 3D structure, respectively. High performance liquid chromatography (HPLC) and gas chromatography-mass spectrometer (GC–MS) were used to analyze the cellulose degradation products. Further research is needed to elucidate the cellulose degradation mechanism and to develop industrial applications for lignocellulosic biomass degradation and waste management.

Power transformer cellulosic insulation destruction assessment using a calculated index composed of CO, CO2, 2-Furfural, and Acetylene

Power transformer insulation is degraded and decomposed over time. Due to the importance of cellulose, indicators such as 2-Furfural, CO, CO2, and CO2/CO ratio are used to investigate cellulose aging status because these are cellulose degradation products. However, various studies have shown that using each of these indicators alone may lead to incorrect cellulose degradation diagnosis. Therefore, a new calculated index called CFA index (an abbreviation of Carbon, Furfural, and Acetylene) that considers the effects of four indicators (CO, CO2, 2-furfural, acetylene) together will be presented in this paper. The CFA index has been obtained from the analysis of 216 power transformer measurement data using the correlation coefficients calculation. The reason for considering acetylene is the importance of its production and the high correlation coefficient between acetylene and transformer age. In this method, if the transformer has the CFA index between −2 and −5.3, then it can be ensured that the transformer does not suffer from severe cellulose aging or decomposition. The normal range for the CFA index is obtained from investigating data from many power transformers, all with CO2/CO ratio between 3 and 10. Finally, to verify the accuracy of the CFA index and its ability to detect cellulosic insulation degradation and the inefficiency of other methods in some cases, dissolved gas analysis (DGA) test results of 306 power transformers will be investigated, and results will be fully presented.

Изучение кинетики термической и термоокислительной деструкции обработанной антипиренами и необработанной древесины

Разработана экспериментальная методика определения механизма огнезащитного действия антипиренов на основе изучения кинетики термической и термоокислительной деструкции древесины. Отработка методики проведена на антипирене MgCl (бишофит). Методика основывается на количественной оценке при термическом разложении древесины выхода продуктов деструкции: CO, CO, дымового аэрозоля. В качестве приборной базы используются хроматографы, фотометр фотоэлектрический для аэрозолей, спектрофотометр. Water with various additives is used during extinguishing forest fires. Fire-retardants are used as additives in most cases. The selection of fire-retardants depends on the level of increase in extinguishing effectiveness at their addition to water. The purpose of this work is to develop an experimental method for evaluating the fireproof effect of flame retardants solutions. This method is based on the investigation of the kinetics of thermal and thermo-oxidative degradation of treated wood with flame retardants and untreated wood. In practice, bischofite and diammonium phosphate are often used as additives. Investigations were conducted using MgCl (bischofite). The explanation of the fireproof effect of the bischofite solution is based on the study of the yield of decomposition products (CO, CO, smoke aerosol) of wood treated with fire-retardant and untreated wood. The instrument base includes chromatographs «Gasochrom 3101», «Tsvet 152», photoelectric photometer for aerosols, spectrophotometer IKS-29. Wood samples were subjected to thermal and thermo-oxidative degradation in nitrogen flow or air flow with a volume velocity of 60 ml · min. Pulse heating in the pyrolysis furnace was carried out in the temperature range from 350 to 550 °C. The significant increase in fire resistance of wood treated with fire-retardant was found as a result of researches using the proposed method. It was shown that the theory of the coating layer, thermal and gas theory of catalytic dehydration are not suitable for explaining the mechanism of fireproof action of an aqueous solution of magnesium halides. Although it is not excluded the inhibition of gas-phase oxidation of cellulose degradation products by hydrogen halides released when heating aqueous solutions of magnesium halides.

Insight into biodegradation of cellulose by psychrotrophic bacterium Pseudomonas sp. LKR-1 from the cold region of China: optimization of cold-active cellulase production and the associated degradation pathways

In the cold regions of China, many lignocellulose-rich agricultural residues, such as corn stover, cannot be efficiently degraded due to low temperature. As the component of cellulose in corn stover was approximately 50%, the degradation of cellulose was considered as one of the most important processes in degrading corn stover. In this work, a psychrotrophic bacterial strain was screened from the soil in the cold region of China and identified as a Pseudomonas sp. named LKR-1, which is able to produce cold-active cellulase. To improve cellulase production, the fermentation conditions were optimized using the Box–Behnken design of the response surface methodology. The maximum cellulase activity was observed after 4 days of incubation at 13.7 °C and pH 7.6 with 8.18 g/L cellulose. HPLC, GC–MS and FTIR spectroscopy were used to describe the changes in residual cellulose and the products of cellulose degradation. In addition to glucose and cellobiose, 24 kinds of compounds were detected during cellulose degradation by psychrotrophic Pseudomonas sp. LKR-1. Furthermore, on the basis the data and references, the possible pathways of degradation by the psychrotrophic strain LKR-1 were speculated, which will help clarify and explain the mechanism of cellulose degradation by psychrotrophic bacteria. This result will provide valuable information that contributes to the exploration of the microbial degradation of corn stover polysaccharides in cold areas.

Degradation mechanism of lignocellulose in dairy cattle manure with the addition of calcium oxide and superphosphate.

Cellulose and lignin belongs to refractory organic matters in the traditional composting. In this research, the degradation of lignocellulose in dairy cattle manure was investigated through adding calcium oxide (CaO) and superphosphate (SSP). In the presence of CaO and SSP, the degradation rate of cellulose and lignin were improved by 25.0% and 8.33%, respectively. The results indicated that the pH value in system would be slightly higher with the addition of CaO and SSP. Besides, the pH value of all cow manure piles were about 8.4 after composting rotten, which could be well neutralized by the gradually acidified soil in the southwest of China with the full effect of fertilizer released. In addition, the abundance of Bacillales, Actinomycetes, and Thermoactinomycetaceae in the experimental groups (AR) was slightly better than that in the control groups (CK) during composting, which led to a conclusion that an elaborate physical-chemical-multivariate aerobic microorganism evolution model of cellulose degradation products (PCMC) was deduced and the physical-chemical-multivariate aerobic microorganism model of lignin cycle degradation (PCML) was developed.

Homoethanol production from cellobionate and glycerol using recombinant Klebsiella oxytoca strains

Cellobionic acid, an oxidized cellulose degradation product, can be produced from cellulosic biomass. Engineered strains of Klebsiella oxytoca BW21 and WT26 can effectively use cellobionate for ethanol production. However, because cellobionate is a more oxidized substrate than cellobiose, oxidized products such as acetate must be produced as by-products to maintain the overall redox balance, and homoethanol production is not possible. One of the strategies to avoid the redox imbalance problem and achieve homoethanol production is co-fermentation of cellobionate with a more reduced substrate glycerol. When cellobionate and glycerol were used as the carbon source by K. oxytoca BW 21, ethanol yield was about 62%–67%. Co-utilization of cellobionate and glycerol in batch fermentation increased the yield of ethanol to about 77% and substantially decreased the accumulation of by-products (such as acetate and 1,3-propanediol). However, glycerol imposes carbon catabolite repression on cellobionate utilization. The utilization rate mismatch between these two substrates limits the benefits of redox recycling between the two substrates’ utilization pathways. When recombinant strain WT26 (which is disabled in glycerol utilization when fermented alone) was used to co-ferment cellobionate and glycerol, the two substrates’ utilization rates exactly matched, which led to an ethanol yield improvement to 96%.

Biochemical Characterization of a Novel Monospecific Endo-β-1,4-Glucanase Belonging to GH Family 5 From a Rhizosphere Metagenomic Library.

Cellulases have a broad range of different industrial applications, ranging from food and beverages to pulp and paper and the biofuels area. Here a metagenomics based strategy was used to identify the cellulolytic enzyme CelRH5 from the rhizosphere. CelRH5 is a novel monospecific endo-β-1,4-glucanase belonging to the glycosyl hydrolase family 5 (GH5). Structural based modeling analysis indicated that CelRH5 is related to endo-β-1,4-glucanases derived from thermophilic microorganisms such as Thermotoga maritima, Fervidobacterium nodosum, and Ruminiclostridium thermocellum sharing 30-40% amino acid sequence identity. The molecular weight of the enzyme was determined as 40.5 kDa. Biochemical analyses revealed that the enzyme displayed good activity with soluble forms of cellulose as a substrate such as ostazin brilliant red hydroxyethyl cellulose (OBR-HEC), carboxymethylcellulose (CMC), hydroxyethyl cellulose (HEC), and insoluble azurine cross-linked hydroxyethylcellulose (AZCL-HEC). The enzyme shows highest enzymatic activity at pH 6.5 with high pH tolerance, remaining stable in the pH range 4.5–8.5. Highest activity was observed at 40°C, but CelRH5 is psychrotolerant being active and stable at temperatures below 30°C. The presence of the final products of cellulose hydrolysis (glucose and cellobiose) or metal ions such as Na+, K+, Li+, and Mg2+, as well as ethylenediaminetetraacetic acid (EDTA), urea, dithiothreitol (DTT), dimethyl sulfoxide (DMSO), 2-mercaptoethanol (2-ME) or glycerol, did not have a marked effect on CelRH5 activity. However, the enzyme is quite sensitive to the presence of 10 mM ions Zn2+, Ni2+, Co2+, Fe3+ and reagents such as 1 M guanidine HCl, 0.1% sodium dodecyl sulfate (SDS) and 20% ethanol. Given that it is psychrotolerant and retains activity in the presence of final cellulose degradation products, metal ions and various reagents, which are common in many technological processes; CelRH5 may be potential suitability for a variety of different biotechnological applications.

Wet treatment of 19th century albumen photographs with Gellan gum hydrogel: A comparison to water treatment

Abstract In the conservation practice of albumen photographs, wet cleaning techniques were long used to remove pollutions, gluing components, cellulose degradation products, and to reduce highlight yellowing. However, water immersion, as well as surface cleaning, enhances the cracking of the albumen layer surface. These cleaning methods are suitable for paper artworks. Whereas the conventional water treatment may cause irreversible damage of the paper structure, the use of rigid hydrogel of Gellan gum had been proposed as an alternative technique that is less destructive to the paper structure. Two wet treatments, water and Gellan gum hydrogel, were applied to the samples of original 19th century albumen photoprints. Their effect was assessed using instrumental methods, such as Fourier transform infrared spectroscopy, laser confocal microscopy, scanning electron microscopy, atomic force microscopy, and pH measurements. The effect of wet treatments on the albumen photograph surface cracking was quantified. Despite that Gellan hydrogel is very gentle and efficient tool for the restoration of paper artworks, it is as harmful for the albumen photographs surface as the conventional water surface cleaning, and therefore may be applied on the verso of the photographs solely.