Cellulosic Substrates Research Articles

Ability of rhizosphere fungi isolated from Swietenia mahagoni litter to produce organic matter-degradating enzymes

In general, soil is inhabited by various microorganism, including fungi, which greatly influence the plant growth. Fungi producing enzymes are very helpful in term of decomposition process. The composting process requires an activator in organic matter decompotion. To determine wheater fungi produce enzymes, it is necessary to evaluate the activity of the enzyme substrates in the fungi particularly producing cellulose, amylase, chitinase and pectinase enzymes. To assess enzyme production, those isolates were inoculated onto Czapek Dox Agar (CDA) media added with Triphenylmethane dyes, as well as cellulose, starch, chitin and pectin substrates. The results of this study revealed that the genus Rhizopus and Fusarium were the most effective fungi producing cellulase, amylase, chitinase, and pectinase. This study is the first report on the fungal activities degrading organic matter isolated from S. mahagony.

Production of Gloeophyllum trabeum Endoglucanase Cel12A in Nicotiana benthamiana for Cellulose Degradation.

Lignocellulosic biomass from plants has been used as a biofuel source and the potent acidic endoglucanase GtCel12A has been isolated from Gloeophyllum trabeum, a filamentous fungus. In this study, we established a plant-based platform for the production of active GtCel12A fused to family 3 cellulose-binding module (CBM3). We used the signal sequence of binding immunoglobulin protein (BiP) and the endoplasmic reticulum (ER) retention signal for the accumulation of the produced GtCel12A in the ER. To achieve enhanced enzyme expression, we incorporated the M-domain of the human receptor-type tyrosine-protein phosphatase C into the construct. In addition, to enable the removal of N-terminal domains that are not necessary after protein expression, we further incorporated the cleavage site of Brachypodium distachyon small ubiquitin-like modifier. The GtCel12A-CBM3 fusion protein produced in the leaves of Nicotiana benthamiana exhibited not only high solubility but also efficient endoglucanase activity on the carboxymethyl cellulose substrate as determined by 3,5-dinitrosalicylic acid assay. The endoglucanase activity of GtCel12A-CBM3 was maintained even when immobilized on microcrystalline cellulose beads. Taken together, these results indicate that GtCel12A endoglucanase produced in plants might be used to provide monomeric sugars from lignocellulosic biomass for bioethanol production.

A Cellulose-Derived Nanofibrous MnO2-TiO2-Carbon Composite as Anodic Material for Lithium-Ion Batteries.

A bio-inspired nanofibrous MnO2-TiO2-carbon composite was prepared by utilizing natural cellulosic substances (e.g., ordinary quantitative ashless filter paper) as both the carbon source and structural matrix. Mesoporous MnO2 nanosheets were densely immobilized on an ultrathin titania film precoated with cellulose-derived carbon nanofibers, which gave a hierarchical MnO2-TiO2-carbon nanoarchitecture and exhibited excellent electrochemical performances when used as an anodic material for lithium-ion batteries. The MnO2-TiO2-carbon composite with a MnO2 content of 47.28 wt % exhibited a specific discharge capacity of 677 mAh g−1 after 130 repeated charge/discharge cycles at a current rate of 100 mA g−1. The contribution percentage of MnO2 in the composite material is equivalent to 95.1% of the theoretical capacity of MnO2 (1230 mAh g−1). The ultrathin TiO2 precoating layer with a thickness ca. 2 nm acts as a crucial interlayer that facilitates the growth of well-organized MnO2 nanosheets onto the surface of the titania-carbon nanofibers. Due to the interweaved network structures of the carbon nanofibers and the increased content of the immobilized MnO2, the exfoliation and aggregation, as well as the large volume change of the MnO2 nanosheets, are significantly inhibited; thus, the MnO2-TiO2-carbon electrodes displayed outstanding cycling performance and a reversible rate capability during the Li+ insertion/extraction processes.

Multicomponent nanoparticles as means to improve anaerobic digestion performance

Sufficient quantity of trace metals is essential for a well performing anaerobic digestion (AD) process. Among the essential trace elements in active sites of multiple important enzymes for AD are iron and nickel ions. In the present study, iron and nickel in the form of Fe2O3 and NiO were coated on TiO2 nanoparticles to be used in batch and continuous operation mode. The effect of TiO2, Fe2O3–TiO2, and NiO–TiO2 nanoparticles on each step of AD process was assessed utilizing simple substrates (i.e. cellulose, glucose, acetic acid, and mixture of H2–CO2) as well as complex ones (i.e. municipal biopulp). The hydrolysis rate of cellulose substrate increased with higher dosages of the coated TiO2 with both metals. For instance, the hydrolysis rate was increased up to 54% at Fe2O3–TiO2 and at a concentration of 23.5 mg/L for NiO–TiO2 it was increased up to 58%, while higher dosage suppressed the hydrolytic activity. Experimental results revealed that low dosages of NiO–TiO2 increased the accumulated methane production up to 24% probably by increasing the enzymatic activity of acetoclastic methanogenesis. NiO–TiO2 showed positive effect on batch and continuous AD of biopulp and improved methane yield up to 8%.

Hydrogen production during direct cellulose fermentation by mixed bacterial culture: The relationship between the key process parameters using response surface methodology

Dark fermentation is a promising method to produce hydrogen from lignocellulosic biomass. This study assessed the influence of temperature, phosphate buffer concentration and substrate concentration on direct hydrogen production form cellulose using response surface methodology. Mixed bacterial culture was successfully enriched on cellulose and used as an inoculum for hydrogen production. The model indicated that the highest cumulative hydrogen production (CHP) of 2.14 L H2/Lmedium could be obtained at 13.5 gcellulose/L, 79.5 mM buffer and 32.6 °C. However, hydrogen yield is then only 0.58 mol H2/molhexose due to low substrate conversion efficiency (SCE). Simultaneous optimization of CHP and SCE with desirability function approach resulted in the H2 yield of 2.71 ± 0.1 mol H2/molhexose and 93.8 ± 1.8% SCE at 3.35 gcellulose/L, 69 mM buffer and 32.9 °C. Phosphate concentration above 80 mM decreased H2 production, but had positive effect on cellulose consumption. The bacterial community analysis showed that Ruminiclostridium papyrosolvens was responsible for cellulose hydrolysis. Lachnoclostridium sp. was positively correlated with ethanol production at high phosphate buffer concentration, while Caproiciproducens sp. with caproate production at low buffer concentration. The obtained results opens the possibility of simultaneous hydrogen and caproate production from cellulosic substrates.

Diazo-Based Copolymers for the Wet Strength Improvement of Paper Based on Thermally Induced CH-Insertion Cross-Linking.

We present an alternative to commonly used, but from an environmental point of view, problematic wet strength agents, which are usually added to paper to prevent a loss of mechanical stability and finally disintegrate when they get into contact with water. To this end, diazoester-containing copolymers are generated, which are coated onto paper and by heating to 110-160 °C for short periods of time become activated and form carbene intermediates, which undergo a CH-insertion cross-linking reaction. The process leads to a simultaneous cross-linking of the polymer and its attachment to the cellulose substrate. The immobilization process of copolymers consisting of a hydrophilic matrix based on N,N-dimethylacrylamide and a diazoester-based comonomer to a cellulose model surface and to laboratory-engineered, fibrous paper substrates is investigated as a function of time, temperature, and cross-linker composition. The distribution of the polymer in the fiber network is studied using confocal fluorescence microscopy. Finally, the tensile properties of modified wet and dry eucalyptus sulfate papers are measured to demonstrate the strong effect of the thermally cross-linked copolymers on the wet strength of paper substrates. Initial experiments show that the tensile indices of the modified and wetted paper samples are up to 50 times higher compared to the values measured for unmodified samples. When dry and wet papers coated with the above-described wetting agents are compared, relative wet strengths of over 30% are observed.

Fabrication of cellulose@Mg(OH)2 composite filter via interfacial bonding and its trapping effect for heavy metal ions

The utilization of renewable biomass cellulose in treating pollution of heavy metal ions (HMIs) is one of overarching and appealing strategies, because it simultaneously satisfies sustainable development and resolves ever-increasing environmental issue. In this regard, the composite cellulose@Mg(OH)2 was prepared via a facile method and explored for its use as water treatment agent. It is demonstrated that the smaller and thinner hexagonal Mg(OH)2 flakes are constructed onto the cellulose substrate by self-assembling; two components are chemically coupled via hydrogen bonds and Mg-Oc (cellulose oxygen) dative bonds; what’s more, the coupling of cellulose with Mg(OH)2 (101) facet is much more preferential than with (001) facet. The resultant composite material shows remarkable HMI removal performance: large capacities of 734.9, 595.8 and 1473.1 mg g−1 for Cd2+, Cu2+ and Pb2+, respectively. Further assisted by good shaping property of the cellulose substrate, the composite is capable of being made into filter, which practically separates HMIs and purifies wastewater with high removal efficiency (99.99%) for Cd2+ even after operating for 110 days and potable water can be obtained. The mechanism is delineated with removal models and characterizations of HMI-recovered products.

Genomic and transcriptomic analysis of the thermophilic lignocellulose-degrading fungus Thielavia terrestris LPH172

BackgroundBiomass-degrading enzymes with improved activity and stability can increase substrate saccharification and make biorefineries economically feasible. Filamentous fungi are a rich source of carbohydrate-active enzymes (CAZymes) for biomass degradation. The newly isolated LPH172 strain of the thermophilic Ascomycete Thielavia terrestris has been shown to possess high xylanase and cellulase activities and tolerate low pH and high temperatures. Here, we aimed to illuminate the lignocellulose-degrading machinery and novel carbohydrate-active enzymes in LPH172 in detail.ResultsWe sequenced and analyzed the 36.6-Mb genome and transcriptome of LPH172 during growth on glucose, cellulose, rice straw, and beechwood xylan. 10,128 predicted genes were found in total, which included 411 CAZy domains. Compared to other fungi, auxiliary activity (AA) domains were particularly enriched. A higher GC content was found in coding sequences compared to the overall genome, as well as a high GC3 content, which is hypothesized to contribute to thermophilicity. Primarily auxiliary activity (AA) family 9 lytic polysaccharide monooxygenase (LPMO) and glycoside hydrolase (GH) family 7 glucanase encoding genes were upregulated when LPH172 was cultivated on cellulosic substrates. Conventional hemicellulose encoding genes (GH10, GH11 and various CEs), as well as AA9 LPMOs, were upregulated when LPH172 was cultivated on xylan. The observed co-expression and co-upregulation of genes encoding AA9 LPMOs, other AA CAZymes, and (hemi)cellulases point to a complex and nuanced degradation strategy.ConclusionsOur analysis of the genome and transcriptome of T. terrestris LPH172 elucidates the enzyme arsenal that the fungus uses to degrade lignocellulosic substrates. The study provides the basis for future characterization of potential new enzymes for industrial biomass saccharification.

Development of sponge-like cellulose colorimetric swab immobilized with anthocyanin from red-cabbage for sweat monitoring

Novel sponge-like biochromic swab was developed via immobilization of natural anthocyanin (Cy) biomolecular probe into microporous cellulose aerogel. The current biosensor is characterized with simple preparation, environmentally-friendly, biocompatibility, biodegradability, flexibility, portability and reversibility. This biochromic sponge-like aerogel detector displayed a color change from pink to green-yellow in response to the biochemical changes occurs to sweat. This could be ascribed to intramolecular charge transfer occurs to the molecular system of Cy. Thus, the anthocyanin probe displayed colorimetric variations in UV–Vis absorption spectra via a blue shifting from 620 to 529 nm when raising the pH value of the prepared mimic sweat solution. Natural pH sensitive anthocyanin spectroscopic probe was extracted from red-cabbage plant, characterized by HPLC, and encapsulated into microporous cellulose. The microporous sponge-like cellulose swab was prepared by activating wood pulp utilizing phosphoric acid, and then subjected to freeze-drying. This anthocyanin probe is highly soluble in water. Thus, it was encapsulated as a direct dye into cellulose substrate during the freeze-drying process. To allow a better fixation of this water-soluble anthocyanin probe to the cellulose substrate, potash alum was added to the freeze-dried mixture to act as a fixing agent or mordant (M) generating Cy/M coordination complex. The produced Cy/M nanoparticles (NPs) were explored by transmission electron microscopy (TEM). The morphological features of the generated aerogels were investigated by scan electron microscope (SEM), energy-dispersive X-ray (EDX) spectra, and Fourier-transform infrared spectra (FT-IR). The cytotoxicity of the prepared aerogel-based biosensor was also evaluated. The naked-eye colorimetric changes were studied by exploring color strength, UV–Vis spectra and CIE Lab colorimetric coordinates.

Metal Affinity Immobilization of the Processive Endoglucanase EG5C-1 from Bacillus subtilis on a Recyclable pH-Responsive Polymer

Establishing a suitable immobilization strategy to improve the accessibility of immobilized cellulase for insoluble cellulose and subsequently recover the enzyme from the remaining substrate is crucial to promote the industrialization of biofuels. Here, using iminodiacetic acid (IDA) and Ni2+ ions, a novel metal-chelated copolymer of methacrylic acid and methyl methacrylate was prepared for the immobilization of His-tagged processive endoglucanase EG5C-1 via affinity interaction between polyhistidine tag and Ni2+. The optimum loading capacity of the functionalized polymer (Eud-IDA-Ni2+) for EG5C-1 was about 280 mg/g, where more than 80% of the activity was recovered. Immobilized EG5C-1 exhibited improved thermal and pH stability and better reusability than the free one, and after five cycles of usage, the hydrolysis productivity remained above 70% of the initial value. The Eud-IDA-Ni2+/EG5C-1 biocomposite displayed reversibly soluble–insoluble characteristics with pH change, which was in the soluble state during the enzyme reaction process but could be recovered in an insoluble form by lowering the pH after the reaction. Thus, the yield obtained from the hydrolysis of an insoluble phosphoric acid-swollen cellulose substrate was similar for the free and immobilized form of EG5C-1. Our combined results suggested that a metal-ion-chelated, pH-responsive polymer had the potential for His-tagged cellulase immobilization to improve both the operational efficiency and economic benefit of the cellulosic biorefinery industry.

Metagenomic Discovery and Characterization of Multi-Functional and Monomodular Processive Endoglucanases as Biocatalysts

Biomass includes cellulose, hemicelluloses, pectin and lignin; constitutes the components of dietary fibre of plant and alge origins in animals and humans; and can potentially provide inexhaustible basic monomer compounds for developing sustainable biofuels and biomaterials for the world. Development of efficacious cellulases is the key to unlock the biomass polymer and unleash its potential applications in society. Upon reviewing the current literature of cellulase research, two characterized and/or engineered glycosyl hydrolase family-5 (GH5) cellulases have displayed unique properties of processive endoglucanases, including GH5-tCel5A1 that was engineered and was originally identified via targeted genome sequencing of the extremely thermophilic Thermotoga maritima and GH5-p4818Cel5_2A that was screened out of the porcine hindgut microbial metagenomic expression library. Both GH5-tCel5A1 and GH5-p4818Cel5_2A have been characterized as having small molecular weights with an estimated spherical diameter at or < 4.6 nm; being monomodular without a required carbohydrate-binding domain; and acting as processive β-1,4-endoglucanases. These two unique GH5-tCel5A1 and GH5-p4818Cel5_2A processive endocellulases are active in hydrolyzing natural crystalline and pre-treated cellulosic substrates and have multi-functionality towards several hemicelluloses including β-glucans, xylan, xylogulcans, mannans, galactomannans and glucomannans. Therefore, these two multifunctional and monomodular GH5-tCel5A1 and GH5-p4818Cel5_2A endocellulases already have promising structural and functional properties for further optimization and industrial applications.

Durable surface functionalisation and pigment coloration of cellulosic fabrics using bioactive additives

AbstractThe main goal of this study is to develop a facile eco‐friendly method for antibacterial/ultraviolet (UV)‐blocking functionalisation using various green bioactive functional additives namely neem, jojoba, argan, aloe vera, ginger, and tulsi. In addition, pigment coloration of cellulosic substrates including cotton, viscose, cotton/viscose, and cotton/linen using pigment colourants and appropriate printing auxiliaries in one step was used. The experimental results revealed that the durability, improvement in the imparted antibacterial/UV‐blocking functional properties and enhancement in the depth of the obtained pigment prints followed a decreasing order: tulsi > ginger > aloe vera > argan > jojoba > neem ≫ none, keeping other parameters constant. The obtained data also demonstrated that the developed pigment prints exhibited remarkable functionalities and depth of shade after 15 washing cycles. Moreover, it was observed that improvement in the imparted functional and coloration properties were a function of types of cellulosic substrate and the kind of colourant. Scanning electron microscopy (SEM), and energy‐dispersive X‐ray spectroscopy (EDX) analysis for selected samples confirmed the surface modification, morphology changes and immobilisation of the used active ingredients onto the treated substrates.

Ionic Conductive Cellulose Mats by Solution Blow Spinning as Substrate and a Dielectric Interstrate Layer for Flexible Electronics.

Renewable cellulose substrates with submicron- and nanoscale structures have revived interest in paper electronics. However, the processes behind their production are still complex and time- and energy-consuming. Besides, the weak electrolytic properties of cellulose with submicron- and nanoscale structures have hindered its application in transistors and integrated circuits with low-voltage operation. Here, we report a simple, low-cost approach to produce flexible ionic conductive cellulose mats using solution blow spinning, which are used both as dielectric interstrate and substrate in low-voltage devices. The electrochemical properties of the cellulose mats are tuned through infiltration with alkali hydroxides (LiOH, NaOH, or KOH), enabling their application as dielectric and substrate in flexible, low-voltage, oxide-based field-effect transistors and pencil-drawn resistor-loaded inverters. The transistors exhibit good transistor performances under operation voltage below 2.5 V, and their electrical performance is strictly related to the type of alkali ionic specie incorporated. Devices fabricated on K+-infiltrated cellulose mats present the best characteristics, indicating pure capacitive charging of the semiconductor. The pencil-drawn load resistor inverter presents good dynamic performance. These findings may pave the way for a new generation of low-power, wearable electronics, enabling concepts such as the "Internet of Things".

Hydrophobic, moisture resistant and biorenewable paper coating derived from castor oil based epoxy methyl ricinoleate with repulpable potential

After ban on single-use plastics, completely bio-based coating on paper is in great demand to replace the plastics liner and other organic-inorganic hybrid coating. To resolve the issues like moisture, hydrophilicty and repulpability after use, a green, sustainable and hydrophobic bio-coating material for paper substrate has been developed. In this work, silanized castor oil (SCO) and silanized methyl ricinoleate (SMR) bio-resins are synthesized by structural modifications of epoxidized castor oil through transesterification and silanization process, Subsequently, the silylated bio-resins are hydrolysed and subjected to crosslinking with cellulosic paper substrate through condensation process. The coated papers showed hydrophobicity with water contact angle (WCA) up to 97° and strongly moisture resistant (moisture content of 2–3%) nature. Scanning electron microscopy analysis with energy dispersive X-ray spectra confirms the uniform coating of SMR resin with better texture and higher degree of silane grafting. The water vapor transmission rate (WVTR) decreased by 77.5% after coating because of blockage of pores and strong bonding with the cellulosic fibers. Further the coated papers showed adequate thermal stability and better tensile strength for commercial packaging. These coatings are removed by exposing to strong alkali solution at 90 °C and the recyclability potential of the paper is confirmed for reuse. These renewable resourced and eco-friendly coating materials are found to be suitable alternative for paper packaging and other coating applications with circular economy approach.

Plant tannin and chitosan-templated cellulose for improved absorption of UV protective natural chromophores

This study reported a facile and sustainable modification of cellulose by plant tannins and chitosan polymer for higher impregnation of UV protective natural chromophores (UVPNCs) derived from the banana floral stem (BFS). The phytochemical screening demonstrated that BFS extracts have different UVPNCs including condensed tannin, flavonoids, anthocyanin, betacyanin and anthraquinone. The optimized impregnation temperature and time for UVPNCs entrapping were found at 80°C with a time interval of 60 min and the overall inherent fixation rate of UVPNCs was ranging from 53 to 63%. The cellulose substrate templated with plant tannins (extracted from Terminalia chebula and Phyllanthus emblica) and chitosan improved the UVPNCs absorption amount almost 2 and 1.8 folds, respectively, which was expressed in terms of color strength (K/S). Interestingly, the UVPNCs entrapping ability of bio-crosslinked cellulose was also higher than typical metallic salts treated cellulose. The higher absorption mechanism of UVPNCs for tannins (-OH and –COOH) and chitosan (-NH2) templating have been discussed in terms of molecular orientation (TCI, LOI), inter and intra-molecular hydrogen bonding configuration (HBI, EH, R), and the total amount of anchored-UVPNCs which was expressed by the asymmetric factor (AF). The UV shielding property of the UVPNCs impregnated modified cellulose was compared and a maximum of two folds higher UPF value was found in bio-templated cellulose substrate (UPF range = 223 to 459) than metal treated cellulose substrates (UPF range = 163 to 175). Furthermore, the functional durability of UVPNCs impregnated substrates was evaluated in terms of several colorfastness and found very good to excellent grading.

Association of antioxidant monophenolic compounds with β-cyclodextrin-functionalized cellulose and starch substrates

Polysaccharide substrates loaded with antioxidant and antimicrobial compounds, effectively protected by cyclodextrin moieties, can be a long-lasting solution to confer certain properties to fabrics, paper and other materials. β-Cyclodextrin was attached to α-cellulose, bleached pulp and starch by a two-step esterification with a tetracarboxylic acid. The resulting derivatives were characterized by spectroscopy, thermal degradation analysis and capability of phenolphthalein inclusion. The carriers, containing between 89 and 171 μmol of β-cyclodextrin per gram, were loaded with carvacrol, cuminaldehyde, cinnamaldehyde and hydroxytyrosol. From a stoichiometric addition, the percentage of compound retained ranged from 49% (hydroxytyrosol in pulp–cyclodextrin) to 92% (carvacrol in starch–cyclodextrin). Finally, the release rate to aqueous ethanol was measured over eight days and fitted to kinetic models. From the analysis of the mean dissolution time, it can be concluded that inserting β-cyclodextrin units enhanced the long-term holding of phenolic active compounds in carbohydrate matrices.

Improving graphene gas sensors via a synergistic effect of top nanocatalysts and bottom cellulose assembled using a modified filtration technique

Improving graphene properties with nanosized catalysts is of interest for numerous applications, especially chemical sensors. Thus, the aim of this study is to prepare nanocatalysts and assemble them on reduced graphene oxide (RGO) for sensing nitric oxides (NOx). The nanocatalysts used in this study include TiO2 nanoparticles (commercial) with WO3, WS2, and MoS2 nanoflakes (mechanically synthesized). Their decoration on the RGO active channel (forming nanohybrids) was obtained via a modified vacuum filtration technique, in which a small syringe and USB-powered pump were employed to surmount the limitation of the conventional filtration setup in the patternable fabrication of device arrays. Sensing measurements expose a co-effect of the nanocatalysts and the cellulose substrate on our RGO-based paper sensors. That can boost the sensitivity of RGO toward NO (1-10 ppm) and NO2 (0.7–3.5 ppm) but weaken it toward NH3 (2–20 ppm). Particularly among the nanocatalysts, MoS2 nanoflakes made our RGO nanohybrid possessing the fastest response/recovery and the highest selectivity toward NOx at room temperature (25 °C). Generally, this study reveals the synergistic effect of MoS2 and cellulose substrate on the improvement of RGO sensing ability and confirms the aptitude of our sensors for flexible and disposable NOx sensing applications.

Cheap Cellulase Production by <i>Aspergillus</i> sp. VTM1 Through Solid State Fermentation of Coffee Pulp Waste

Coffee pulp biomass waste can easily be found anywhere in Indonesia, considering it is the fourth world's largest coffee exporter. The utilization of coffee pulp is very limited and is categorized as a source of pollutants in water bodies and soils. In contrast, coffee pulp waste is very potential because 63% of the main compound is cellulose. Microbial utilization of this waste for enzyme production purposes, especially cellulase, is a breakthrough that may lead to reduce production costs. Initial investigations showed that Aspergillus sp. VTM1 through solid-state fermentation (SSF) could produce cellulases. Optimal cellulase could be produced if 10 g coffee pulp with 10% moisture is inoculated using 108 spores/mL of Aspergillus sp. VTM1 for 48 hours at 30 °C. Hydrolysis of 1% carboxymethyl cellulose (CMC) substrate in 50 mM acetate buffer pH 5 by this cellulase showed that the enzyme activity reached up to 1.18 U/mL. The optimum pH of the enzyme was 5 and stable at 3-3.5 and 4-7. The success of the first step of this investigation will be a cheap way of producing cellulases.

Comparisons of Catalytic Efficiency during the Reduction of Lignocellulosic Substrates between Free Enzyme and Enzyme bound to Mobile Enzyme Sequestration Platforms (MESP)

The cellulolytic bacterium Clostridium thermocellum employs a flexible cellulosome that can bind a variety of enzymes to breakdown cellulosic biomass. A key feature of the cellulosome is a cohesin (Type 1) – dockerin (Type 1) interaction that binds dockerin-endowed enzymes to the cohesin-ladened scaffoldin backbone. Multiple enzymes of various enzyme classes (e.g., exocellulases, endocellulases, xylanases) can bind to the cellulosome structure for synergistic deconstruction of cellulosic substrates. Several “artificial cellulosomes” have been engineered in an attempt to mimic this system for abiotic decomposition of lignocellulosic substrates. One such engineered system is called a mobile enzyme sequestration platform (MESP). The prototype of this platform was called a “rosettasome”. MESPs are chimera of an archaeal group II chaperonin permutant fused to C. thermocellum cohesin via a 9-12 amino acid linker. The archaeal chaperonin complex is thermotolerant. In prior work our lab demonstrated that binding cellulolytic enzymes to MESPs enhances lignocellulose breakdown efficiency over free enzyme in solution (sans platform). Interestingly, our prior data indicated that MESP systems may also be acidotolerant since substrate was treated with mild sulfuric acid. In this study, we tested the acidotolerance of MESP technology as well as the efficiency of carbohydrate reduction on other feedstock (e.g., rice straw). We also tested our MESPs against the prototype rosettasome to determine if this next-generation platform outperforms the original system. Here we present the results of our comparisons. Understanding the limits of MESP enhancement will direct future engineering of this system for industrial and/or agricultural applications.

Bioprinting of Regenerative Photosynthetic Living Materials

AbstractLiving materials, which are fabricated by encapsulating living biological cells within a non‐living matrix, have gained increasing attention in recent years. Their fabrication in spatially defined patterns that are mechanically robust is essential for their optimal functional performance but is difficult to achieve. Here, a bioprinting technique employing environmentally friendly chemistry to encapsulate microalgae within an alginate hydrogel matrix is reported. The bioprinted photosynthetic structures adopt pre‐designed geometries at millimeter‐scale resolution. A bacterial cellulose substrate confers exceptional advantages to this living material, including strength, toughness, flexibility, robustness, and retention of physical integrity against extreme physical distortions. The bioprinted materials possess sufficient mechanical strength to be self‐standing, and can be detached and reattached onto different surfaces. Bioprinted materials can survive stably for a period of at least 3 days without nutrients, and their life can be further extended by transferring them to a fresh source of nutrients within this timeframe. These bioprints are regenerative, that is, they can be reused and expanded to print additional living materials. The fabrication of the bioprinted living materials can be readily up‐scaled (up to ≥70 cm × 20 cm), highlighting their potential product applications including artificial leaves, photosynthetic bio‐garments, and adhesive labels.