Draft genome sequence of Deinococcus sp. KR-1, a potential strain for palladium-leaching.

Strain KR-1 was isolated from pond water collected in Japan. Because this strain was capable of adsorbing palladium particles in sterilized water, strain KR-1 will be a useful biocatalyst for palladium-leaching from metal waste. Here we present a draft genome sequence of Deinococcus sp. KR-1, which consists of a total of 7 contigs containing 4,556,772 bp with a GC content of 70.0% and comprises 4,450 predicted coding sequences. Based on the 16S rRNA gene sequence analysis, strain KR-1 was identified as Deinococcus sp. KR-1.

Cellulose-Nanofiber-Mediated Sorption-Benefitting Holed Silicalite-1 Crystals.

Silicalite-1-type zeolites with unique intracrystal holes or cracks were successfully prepared using a cellulose nanofiber (CNF) as an additional mediating material, and their vapor phase adsorption properties toward methyl tert-butyl ether (MTBE) and n-nitrosodimethylamine (NDMA) were examined. It was found that the mixing protocol of CNF and structure-directing agents (SDAs), the addition amount of CNF, and the CNF/SDAs amount ratio play important roles in forming the holed silicalite-1. The synthesis route that preliminarily mixes CNF with SDAs in a series of controlled conditions is particularly beneficial for the formation of the holed silicalite-1 with mesoporosity and larger pores because the CNF-SDAs composite structure benefits the zeolite growth closely encompassing CNF inside the crystal structure. It also promotes the preferential formation of the orthorhombic phase vicinal to the CNF surface, namely, the surface of the formed internal holes or cracks, with the twin-type crystal size reduced as compared to the non-CNF-templated sample. On the contrary, the synthesis route that mixes CNF with SDAs-silicate composite ions tends to modify the twin-type crystal shape at the same time to form small but uniform well-crystallized particles with less holes or cracks and a dominative monoclinic phase. It was considered that both the inter-subunit structural defect and silanol defect whose content is increased with CNF addition influence the adsorptivity of MTBE and NDMA. Owing to the small twin-type crystal size, the smaller crystal subunits, and the favored short path from the surface of internal holes or cracks, the holed silicalite-1 derived from the CNF and SDA premixture assures the easiest access of adsorbate molecules to the most energetically favored sites and is most appropriate for the adsorption of both MTBE and NDMA among the examined zeolites.

Properties of natural rubber reinforced with cellulose nanofibers based on fiber diameter distribution as estimated by differential centrifugal sedimentation.

Cellulose nanofibers (CNFs) with different degrees of fibrillation are prepared by the mechanical fibrillation of kraft pulp using wet disk milling, and dispersions of the prepared CNFs were subjected to differential centrifugal sedimentation (DCS) in order to estimate the diameter distributions of the CNFs. The low-fibrillated CNFs (fiber diameter (d): >10 µm) had a weak reinforcing effect on natural rubber (NR), while the medium-fibrillated CNFs (d: 0.1-10 µm) dramatically improve the initial modulus and decrease the elongation at break. The high-fibrillated CNFs (d: <0.1 µm) enhanced the tensile strength even further while maintaining the elongation at break. The reinforcing mechanism of the NR composites reinforced by the CNFs (NR-CNFs) was confirmed by field-emission scanning electron microscopy imaging, dynamic mechanical analysis, and toluene uptake measurements. It was concluded that these characteristic mechanical properties of the NR-CNFs were determined by the morphologies of the CNFs. The branching structure of the medium-fibrillated CNFs affected high improvement of the initial modulus, and the network formed by the high-fibrillated CNFs were involved in enhancement of the tensile strength without compromising viscoelastic properties. Understanding the effect of their diameter distribution can potentially reduce the production cost of CNFs and thus expand their applicability.

Evaluation of the effect of hot-compressed water treatment on enzymatic hydrolysis of lignocellulosic nanofibrils with different lignin content using a quartz crystal microbalance.

Hot-compressed water (HCW) treatment is known to not only improve enzymatic hydrolysis efficiency of lignocellulosic biomass but to also generate insoluble lignin droplets, which retard enzymatic hydrolysis. In this study, the inhibitory effect of the lignin droplets was evaluated by monitoring the initial enzyme adsorption and degradation of lignocellulosic nanofibrils (LCNFs) using a quartz crystal microbalance (QCM). Lignin content was adjusted by the sodium chlorite-acetic acid method and divided into samples with high (24.9 wt%) and low (5.6 wt%) lignin content, which were then subjected to HCW treatment at various temperatures. The changes in lignin content were small with increasing HCW temperature, whereas hemicellulose content decreased, regardless of the initial lignin content. The formation of lignin droplets and pseudo-lignin-like products was confirmed in both LCNFs by atomic force microscopy (AFM) and was predominant in LCNFs with high lignin content treated at 200°C. QCM data showed that the enzyme adsorption amount in both LCNFs after HCW treatment was increased and was greater in LCNFs with low lignin content. Initial enzymatic degradation was substantially slowed in LCNFs with high lignin content, particularly after HCW treatment at temperatures higher than 180°C. These QCM results suggest that the steric hindrance of the deposited lignin is the primary mechanism by which the initial enzymatic hydrolysis is delayed. Biotechnol. Bioeng. 2016;113: 1441-1447. © 2015 Wiley Periodicals, Inc.

Contribution of a family 1 carbohydrate-binding module in thermostable glycoside hydrolase 10 xylanase from Talaromyces cellulolyticus toward synergistic enzymatic hydrolysis of lignocellulose.

BACKGROUND: Enzymatic removal of hemicellulose components such as xylan is an important factor for maintaining high glucose conversion from lignocelluloses subjected to low-severity pretreatment. Supplementation of xylanase in the cellulase mixture enhances glucose release from pretreated lignocellulose. Filamentous fungi produce multiple xylanases in their cellulase system, and some of them have modular structures consisting of a catalytic domain and a family 1 carbohydrate-binding module (CBM1). However, the role of CBM1 in xylanase in the synergistic hydrolysis of lignocellulose has not been investigated in depth. RESULTS: Thermostable endo-ß-1,4-xylanase (Xyl10A) from Talaromyces cellulolyticus, which is recognized as one of the core enzymes in the fungal cellulase system, has a modular structure consisting of a glycoside hydrolase family 10 catalytic domain and CBM1 at the C-terminus separated by a linker region. Three recombinant Xyl10A variants, that is, intact Xyl10A (Xyl10Awt), CBM1-deleted Xyl10A (Xyl10AdC), and CBM1 and linker region-deleted Xyl10A (Xyl10AdLC), were constructed and overexpressed in T. cellulolyticus. Cellulose-binding ability of Xyl10A CBM1 was demonstrated using quartz crystal microbalance with dissipation monitoring. Xyl10AdC and Xyl10AdLC showed relatively high catalytic activities for soluble and insoluble xylan substrates, whereas Xyl10Awt was more effective in xylan hydrolysis of wet disc-mill treated rice straw (WDM-RS). The enzyme mixture of cellulase monocomponents and intact or mutant Xyl10A enhanced the hydrolysis of WDM-RS glucan, with the most efficient synergism found in the interactions with Xyl10Awt. The increased glucan hydrolysis yield exhibited a linear relationship with the xylan hydrolysis yield by each enzyme. This relationship revealed significant hydrolysis of WDM-RS glucan with lower supplementation of Xyl10Awt. CONCLUSIONS: Our results suggest that Xyl10A CBM1 has the following two roles in synergistic hydrolysis of lignocellulose by Xyl10A and cellulases: enhancement of lignocellulosic xylan hydrolysis by binding to cellulose, and the efficient removal of xylan obstacles that interrupt the cellulase activity (because of similar binding target of CBM1). The combination of CBM-containing cellulases and xylanases in a fugal cellulase system could contribute to reduction of the enzyme loading in the hydrolysis of pretreated lignocelluloses.

Synergistic effect of delignification and treatment with the ionic liquid 1-ethyl-3-methylimidazolium acetate on enzymatic digestibility of poplar wood.

This study examined the effects of removing key recalcitrance factors by ionic liquid (IL) treatment on the cellulase digestibility of poplar wood. Ground biomass was subjected to chlorite delignification and IL (1-ethyl-3-methylimidazolium acetate) treatment alone or in combination. The compositional and structural features of differentially treated biomass samples and their hydrolysis performance at various cellulase loadings were investigated. IL treatment caused minor compositional changes but drastically decreased cellulose crystallinity; in particular, when administered after delignification, an X-ray diffractogram similar to that of cellulose II polymorph was observed, suggesting that in the absence of lignin, the cellulose was dissolved in the IL and regenerated in water with a polymorphic transformation. The structural changes induced by the combined delignification-IL treatment facilitated the enzymatic hydrolysis of cellulose; the biomass could be fully degraded within 72 h by 4 FPU of cellulase per gram glucan, with cellobiose degradation being the rate-limiting step.

Simultaneous saccharification and fermentation and a consolidated bioprocessing for Hinoki cypress and Eucalyptus after fibrillation by steam and subsequent wet-disk milling.

An advanced pretreatment method that combines steam treatment (ST) with wet disk milling (WDM) was evaluated using two different species of woods, viz., Hinoki cypress (softwood) and Eucalyptus (hardwood). Bioconversion of the pretreated products was performed using enzymatic saccharification via a commercial cellulase mixture and two types of fermentation processing, i.e., yeast-based simultaneous saccharification and fermentation (SSF) and Clostridium thermocellum-based consolidated bioprocessing (CBP). A higher yield of glucose was obtained in the enzymatic saccharification and fermentation products from SSF and CBP with pretreatment consisting of WDM after ST, as compared to either ST or WDM alone. Maximum ethanol production via SSF and CBP were 359.3 and 79.4 mg/g-cellulose from Hinoki cypress, and 299.5 and 73.1 mg/g-cellulose from Eucalyptus, respectively. While the main fermentation product generated in CBP was acetate, the total products yield was 319.9 and 262.0 mg/g-cellulose from Hinoki cypress and Eucalyptus, respectively.

Thin film of lignocellulosic nanofibrils with different chemical composition for QCM-D study.

Thin films of lignocellulosic nanofibrils (LCNFs) with different chemical compositions were prepared for real-time observation of their enzymatic adsorption and degradation behavior by using a quartz crystal microbalance with dissipation monitoring (QCM-D). LCNFs were obtained by disk milling followed by high-pressure homogenization of Hinoki cypress. The lignin contents were adjusted by the sodium chlorite treatment. The film thickness was adjusted by controlling the concentration of the LCNF suspension, which was determined from its proportional relationship to the UV absorbance of lignin. The enzymatic degradation behavior was investigated with a commercial enzyme mixture. The results of the QCM-D showed that changes in frequency and dissipation in the initial reaction stage were different from the typical changes reported for pure cellulose. To the best of our knowledge, this is the first report of the preparation of thin films of LCNFs with high lignin and hemicellulose contents and their application in a QCM-D study.

Ultrafine cellulose fibers produced by Asaia bogorensis, an acetic acid bacterium.

The ability to synthesize cellulose by Asaia bogorensis, a member of the acetic acid bacteria, was studied in two substrains, AJ and JCM. Although both strains have identical 16S rDNA sequence, only the AJ strain formed a solid pellicle at the air-liquid interface in static culture medium, and we analyzed this pellicle using a variety of techniques. In the presence of cellulase, glucose and cellobiose were released from the pellicle suggesting that it is made of cellulose. Field emission electron microscopy allowed the visualization of a 3D knitted structure with ultrafine microfibrils (approximately 5-20 nm in width) in cellulose from A. bogorensis compared with the 40-100 nm wide microfibrils observed in cellulose isolated from Gluconacetobacter xylinus, suggesting differences in the mechanism of cellulose biosynthesis or organization of cellulose synthesizing sites in these two related bacterial species. Identifying these differences will lead to a better understanding of cellulose biosynthesis in bacteria.