Construction of a Synthetic Microbial Community for Enzymatic Pretreatment of Wheat Straw for Biogas Production via Anaerobic Digestion.

Biological pretreatment is a viable method for enhancing biogas production from straw crops, with the improvement in lignocellulose degradation efficiency being a crucial factor in this process. Herein, a metagenomic approach was used to screen core microorganisms (Bacillus subtilis, Acinetobacter johnsonii, Trichoderma viride, and Aspergillus niger) possessing lignocellulose-degrading abilities among samples from three environments: pile retting wheat straw (WS), WS returned to soil, and forest soil. Subsequently, synthetic microbial communities were constructed for fermentation-enzyme production. The crude enzyme solution obtained was used to pretreat WS and was compared with two commercial enzymes. The synthetic microbial community enzyme-producing pretreatment (SMCEP) yielded the highest enzymatic digestion efficacy for WS, yielding cellulose, hemicellulose, and lignin degradation rates of 39.85, 36.99, and 19.21%, respectively. Furthermore, pretreatment of WS with an enzyme solution, followed by anaerobic digestion achieved satisfactory results. SMCEP displayed the highest cumulative biogas production at 801.16 mL/g TS, which was 38.79% higher than that observed for WS, 22.15% higher than that of solid-state commercial enzyme pretreatment and 25.41% higher than that of liquid commercial enzyme pretreatment. These results indicate that enzyme-pretreated WS can significantly enhance biogas production. This study represents a solution to the environmental burden and energy use of crop residues.

Enhanced enzymatic sugar production from corn stover by combination of water extraction and glycerol-assisted instant catapult steam explosion.

Glycerol-assisted instant catapult steam explosion (ICSE) of lignocellulose is an effective pretreatment method for enhancing sugar production compared to glycerol-free ICSE. In this study, glycerol-assisted ICSE of corn stover was studied in order to understand the reaction mechanisms and further optimize the process. Results showed that water extraction of corn stover prior to ICSE reduced pseudo-lignin formation. The combination of water extraction and glycerol-assisted ICSE led to the formation of lignin with a lower molecular weight (Mw) of 2851 g/mol than 3521 g/mole of that from the combination of water extraction and glycerol-free ICSE. 1H-13C NMR analysis revealed that glycerol likely reacted with lignin carboxylic OHs through esterification while etherification of aliphatic OHs was not observed in ICSE. These lignin analyses indicated that glycerol protected lignin from condensation/repolymerization during glycerol-assisted ICSE. Enzymatic hydrolysis results showed that without water extraction increasing glycerol usage from 0.2 kg/kg stover to 0.4 kg/kg stover improved glucan digestibility to 78% but further increase to 0.5 kg/kg stover reduced glucan digestibility. In addition, at the glycerol usage of 0.2-0.4 kg/kg stover, washing of pretreated stover for removal of glycerol and other biomass-derived compounds did not improve glucan digestibility compared to unwashed ones. Combination of water extraction and glycerol-assisted ICSE led to a high glucan digestibility of 89.7% and a total glucose yield of 25.5 g glucose/100 g stover, which were 30.1% and 7.5 g/100 g stover higher than those derived from glycerol-free ICSE of stover, respectively. Since glycerol is a low-cost carbon source, the resulting enzymatic hydrolysate that contained both glucose and glycerol may be directly used to produce bioproducts by microbial fermentation.

Construction of a synthetic microbial community based on multiomics linkage technology and analysis of the mechanism of lignocellulose degradation.

The efficient degradation of lignocellulose is a bottleneck for its integrated utilization. This research performed species analysis and made functional predictions in various ecosystems using multiomics coupling to construct a core synthetic microbial community with efficient lignocellulose degradation function. The synthetic microbial community was employed to degrade corn straw via solid-state fermentation. The degradation mechanisms were resolved using proteomics. The optimum culture conditions included 10% inoculum level (w/v), 4% nitrogen source ratio and a fermentation time of 23 d. Under these conditions, the degradation rates of cellulose, hemicellulose, and lignin were 34.91%, 45.94%, and 23.34%, respectively. Proteomic analysis revealed that lignin 1,4-ß-xylanase, ß-xylosidase and endo-1,4-ß-xylanase were closely related to lignocellulose degradation. The metabolic pathways involved in lignocellulose degradation and the functional roles of eight strains were obtained. The synthesis of a microbial community via multiomics linkage technology can effectively decompose lignocellulose, which is useful for their further utilization.

Biodegradation of Gramineous Lignocellulose by Locusta migratoria manilensis (Orthoptera: Acridoidea).

Exploring an efficient and green pretreatment method is an important prerequisite for the development of biorefinery. It is well known that locusts can degrade gramineous lignocellulose efficiently. Locusts can be used as a potential resource for studying plant cell wall degradation, but there are few relative studies about locusts so far. Herein, some new discoveries were revealed about elucidating the process of biodegradation of gramineous lignocellulose in Locusta migratoria manilensis. The enzyme activity related to lignocellulose degradation and the content of cellulose, hemicellulose, and lignin in the different gut segments of locusts fed corn leaves were measured in this study. A series of characterization analyses were conducted on corn leaves and locust feces, which included field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction pattern (XRD), and thermogravimetric (TG) analysis. These results showed that the highest activities of carboxymethyl cellulase (CMCase), filter paper cellulase (FPA), and xylanase were obtained in the foregut of locusts, which strongly indicated that the foregut was the main lignocellulose degradation segment in locusts; furthermore, the majority of nutritional components were absorbed in the midgut of locusts. The activity of CMCase was significantly higher than that of xylanase, and manganese peroxidase (MnPase) activity was lowest, which might be due to the basic nutrition of locusts being cellulose and hemicellulose and not lignin based on the results of FE-SEM, FTIR, XRD, and TG analysis. Overall, these results provided a valuable insight into lignocellulosic degradation mechanisms for understanding gramineous plant cell wall deconstruction and recalcitrance in locusts, which could be useful in the development of new enzymatic pretreatment processes mimicking the locust digestive system for the biochemical conversion of lignocellulosic biomass to fuels and chemicals.

Detoxication and bioconversion of aflatoxin B1 by yellow mealworms (Tenebrio molitor): A sustainable approach for valuable larval protein production from contaminated grain.

Yellow mealworm (Tenebrio molitor) is a supplementary protein source for food and feed and represents a promising solution to manage grain contaminated with Aflatoxin B1 (AFB1). In this study, AFB1 present in different concentrations in wheat bran was treated and removed via bioconversion by yellow mealworm of different instars, with emphasis on the bioconversion performance and metabolism of AFB1. Upon application of wheat bran spiked with 100 µg/kg AFB1 to 5th-6th instar yellow mealworms, the conversion rate of AFB1 was up to 87.85 %. Low level of AFB1 (< 2 µg/kg) was accumulated in the larval bodies, and the survival rate, development and nutrition contents of yellow mealworm were not significantly affected. It was revealed that 1 kg of wheat bran contaminated with AFB1 increased the weight of yellow mealworms from 138 g to 469 g, containing approximately 103 g of protein. The bioconversion of AFB1 by yellow mealworms led to generation of 13 metabolites in the frass and 3 metabolites in the larvae. AFB1 was detoxicated and removed via phase I metabolism comprising reduction, dehydrogenation, hydration, demethylation, hydroxylation, decarbonylation and ketoreduction, followed by phase II metabolism involving conjugation of amino acid, glucoside and glutathione (GSH). The toxicity of AFB1 metabolites was deemed lower than that of AFB1 according to their structures. This study provides a sustainable approach and theoretical foundation on using yellow mealworms for cleaner grain contamination management and valuable larval protein production via bioconversion of food and feed contaminated by AFB1.

Improvement of Nicotine Removal and Ethanol Fermentability From Tobacco Stalk by Integration of Dilute Sulfuric Acid Presoak and Instant Catapult Steam Explosion Pretreatment.

The nicotine from tobacco stalk showed obvious inhibitory effect on the activity of cellulase and fermentability of microorganisms, which seriously hinders the utilization of tobacco stalk. Dilute sulfuric acid presoak of tobacco stalk was used to enhance the performance of instant catapult steam explosion (ICSE) for tobacco stalk pretreatment. The presoak was beneficial to break the recalcitrant structure of tobacco stalk, reduce nicotine content to relieve the inhibition on the activity of cellulase and metabolism of microorganisms, and promote the performance of enzymatic hydrolysis and ethanol fermentation. The optimized 0.8% sulfuric acid (w/w) presoak-integrated ICSE pretreatment resulted in 85.54% nicotine removal from tobacco stalk; meanwhile, the total sugar concentration from enzymatic hydrolysis of pretreated tobacco stalk increased from 33.40 to 53.81 g/L (the ratio of dry tobacco stalk to water was 1:8, w/w), ethanol concentration increased 103.36% from 5.95 to 12.10 g/L in flask, compared with separate ICSE pretreatment. Finally, the ethanol concentration achieved the highest 23.53 g/L in a 5-L fermenter with the ethanol yield from the glucose of tobacco stalk hydrolysate achieving 71.40% by increasing the solid loading of the tobacco stalk in the enzymatic hydrolysis process (the ratio of dry tobacco stalk to water was 1:4, w/w). These results achieved the expected purpose of efficient utilization of discarded tobacco stalk.

An Engineered Thermostable Laccase with Great Ability to Decolorize and Detoxify Malachite Green.

Laccases can catalyze the remediation of hazardous synthetic dyes in an eco-friendly manner, and thermostable laccases are advantageous to treat high-temperature dyeing wastewater. A novel laccase from Geothermobacter hydrogeniphilus (Ghlac) was cloned and expressed in Escherichia coli. Ghlac containing 263 residues was characterized as a functional laccase of the DUF152 family. By structural and biochemical analyses, the conserved residues H78, C119, and H136 were identified to bind with one copper atom to fulfill the laccase activity. In order to make it more suitable for industrial use, Ghlac variant Mut2 with enhanced thermostability was designed. The half-lives of Mut2 at 50 °C and 60 °C were 80.6 h and 9.8 h, respectively. Mut2 was stable at pH values ranging from 4.0 to 8.0 and showed a high tolerance for organic solvents such as ethanol, acetone, and dimethyl sulfoxide. In addition, Mut2 decolorized approximately 100% of 100 mg/L of malachite green dye in 3 h at 70 °C. Furthermore, Mut2 eliminated the toxicity of malachite green to bacteria and Zea mays. In summary, the thermostable laccase Ghlac Mut2 could effectively decolorize and detoxify malachite green at high temperatures, showing great potential to remediate the dyeing wastewater.

Reassessment of the role of CaCO3 in n-butanol production from pretreated lignocellulosic biomass by Clostridium acetobutylicum.

In this study, the role of CaCO3 in n-butanol production was further investigated using corn straw hydrolysate (CSH) media by Clostridium acetobutylicum CICC 8016. CaCO3 addition stimulated sugars utilization and butanol production. Further study showed that calcium salts addition to CSH media led to the increase in Ca2+ concentration both intracellularly and extracellularly. Interestingly, without calcium salts addition, intracellular Ca2+ concentration in the synthetic P2 medium was much higher than that in the CSH medium despite the lower extracellular Ca2+ concentrations in the P2 medium. These results indicated that without additional calcium salts, Ca2+ uptake by C. acetobutylicum CICC 8016 in the CSH medium may be inhibited by non-sugar biomass degradation compounds, such as furans, phenolics and organic acids. Comparative proteomics analysis results showed that most enzymes involved in glycolysis, redox balance and amino acids metabolism were up-regulated with CaCO3 addition. This study provides further insights into the role of CaCO3 in n-butanol production using real biomass hydrolysate.

Effect of chlorogenic acid on alleviating inflammation and apoptosis of IPEC-J2 cells induced by deoxyniyalenol.

Deoxynivalenol (DON) is extensively detected in many kinds of foods and feeds to harm human and animal health. This research aims to investigate the effect of chlorogenic acid (CGA) on alleviating inflammation and apoptosis of swine jejunal epithelial cells (IPEC-J2) triggered by DON. The results demonstrated that cell viability was decreased when DON concentrations increased or incubation time expanded. The pretreatment with CGA (40 µg/mL) for 1 h increased cell viability, decreased lactate dehydrogenase (LDH) release and apoptosis in cells triggered by DON at 0.5 µg/mL for 6 h, compared with the DON alone-treated cells. Moreover, the mRNA abundances of IL-8, IL-6, TNF-α, COX-2, caspase-3, Bax and ASCT2 genes, and protein expressions of COX-2, Bax and ASCT2 were significantly down-regulated; while the mRNA abundances of ZO-1, claudin-1, occludin, PePT1 and GLUT2 genes, and protein expressions of ZO-1, claudin-1 and PePT1 were significantly up-regulated in the CGA + DON group, compared with the DON alone group. This study indicated that CGA pretreatment alleviated cytotoxicity, inflammation and apoptosis in DON-triggered IPEC-J2 cells, and protected intestinal cell integrity from DON damages.

The 206 kbp mitochondrial genome of Phanerochaete carnosa reveals dynamics of introns, accumulation of repeat sequences and plasmid-derived genes.

In this study, the mitogenome of Phanerochaete carnosa was sequenced and assembled by the next-generation sequencing. The P. carnosa mitogenome was composed of circular DNA molecules, with a total size of 206,437 bp. Intron sequence, repeat sequence and plasmid-derived genes together promoted the P. carnosa mitogenome to become the second largest mitogenome in Basidiomycota. Gene arrangement analysis revealed large-scale gene rearrangements between Polyporales mitogenomes, and P. carnosa contained a unique gene order. The number and position classes of introns varied between 14 Polyporales species tested, indicated numerous intron loss/gain events occurred in the evolution of Polyporales. Most core PCGs in the 14 Polyporales species we tested were found subjected to purifying selection. However, the Ka/Ks values of rps3 gene were found >1 between some Polyporales species, indicating pressure of positive selection may exist. Phylogenetic analysis based on the combined mitochondrial gene set obtained well-supported tree topologies, and P. carnosa was identified as a sister species to Phlebia radiata. This study served as the first report on the mitogenome in the family Phanerochaetaceae, which will promote the understanding of the phylogeny, population genetics, and evolution of this white-rot fungus and related fungi.

Effect of detoxification methods on ABE production from corn stover hydrolysate by Clostridium acetobutylicum CICC 8016.

In this study, effects of different single biomass derived inhibitors on acetone-butanol-ethanol (ABE) production by Clostridium acetobutylicum CICC 8016 were first investigated. The results showed that formic acid, coumaric acid, and furfural at 0.5 g/L (sodium formate equivalent) inhibited ABE production. Furthermore, corn stover hydrolysate media were prepared following dilute acid pretreatment, enzymatic hydrolysis, and detoxification with different methods. Among overliming, steam stripping, acetone-ethyl ether extraction, and ion exchange with five anion resins, adsorption with resin D301 showed the highest efficiency for inhibitor removal (99-100% of phenolics and 87-99% of sugar degradation products). Without detoxification, ABE production was lower than 1.0 g/L from 28.1 g/L sugars whereas ABE production with medium detoxified by D301 resin achieved higher ABE concentrations and yields than control with synthetic medium. Correlation analysis further revealed that formic acid, coumaric acid, and total phenolics were the major compounds inhibiting ABE production. The results also showed that the single detoxification method was sufficient to detoxify the hydrolysate for ABE production at the pretreatment conditions used in this study.

Effect of Compound Probiotics and Mycotoxin Degradation Enzymes on Alleviating Cytotoxicity of Swine Jejunal Epithelial Cells Induced by Aflatoxin B1 and Zearalenone.

Zearalenone (ZEA) and aflatoxin B1 (AFB1) are two main kinds of mycotoxins widely existing in grain and animal feed that cause a lot of economic loss and health problems for animals and humans. In order to alleviate the cytotoxic effects of AFB1 and ZEA on swine jejunal epithelial cells (IPEC-J2), the combination of a cell-free supernatant of compound probiotics (CFSCP) with mycotoxin degradation enzymes (MDEs) from Aspergillus oryzae was tested. The results demonstrated that coexistence of AFB1 and ZEA had synergetic toxic effects on cell viability. The cell viability was decreased with mycotoxin concentrations increasing, but increased with incubation time extension. The necrotic cell rates were increased when 40 µg/L AFB1 and/or 500 µg/L ZEA were added, but the addition of CFSCP + MDE suppressed the necrotic effects of AFB1 + ZEA. The viable cell rates were decreased when AFB1 and/or ZEA were added: However, the addition of CFSCP + MDE recovered them. The relative mRNA abundances of Bcl-2, occludin, and ZO-1 genes were significantly upregulated, while Bax, caspase-3, GLUT2, ASCT2, PepT1, and IL6 genes were significantly downregulated by CFSCP + MDE addition, compared to the groups containing 40 µg/L AFB1 and 500 µg/L ZEA. This research provided an effective strategy in alleviating mycotoxin cytotoxicity and keeping normal intestinal cell structure and animal health.

Enhanced production of succinic acid from methanol-organosolv pretreated Strophanthus preussii by recombinant Escherichia coli.

A biorefinery process for high yield production of succinic acid from biomass sugars was investigated using recombinant Escherichia coli. The major problem been addressed is utilization of waste biomass for the production of succinic acid using metabolic engineering strategy. Here, methanol extract of Strophanthus preussii was used for fermentation. The process parameters were optimized. Glucose (9 g/L), galactose (4 g/L), xylose (6 g/L) and arabinose (0.5 g/L) were the major sugars present in the methanol extract of S. preussii. E. coli K3OS with overexpression of soluble nucleotide pyridine transhydrogenase sthA and mutation of lactate dehydrogenase A (ldhA), phosphotransacetylase acetate kinase A (pta-ackA), pyruvate formate lyase B (pflB), pyruvate oxidase B (poxB), produced a final succinic acid concentration of 14.40 g/L and yield of 1.10 mol/mol total sugars after 72 h dual-phase fermentation in M9 medium. Here, we show that the maximum theoretical yield using methanol extracts of S. preussii was 64%. Hence, methanol extract of S. preussii could be used for the production of biochemicals such as succinate, malate and pyruvate.

Availability of lignocellulose from forestry waste for use as a biofuel in China.

Biomass is a very important renewable energy and plays an important role in the energy structure of China. Here, the role of forestry waste in producing energy in China was analyzed and the availability of forestry waste for biofuel production, theoretically collectable amounts of forest biomass, and density of forestry waste were assessed. Agricultural and forestry waste are important biomass resources. The potential for using forestry waste as a low cost substrate for producing fuel ethanol using existing forestry resources and techniques was analyzed, and the feasibility of producing fuel ethanol in different Chinese provinces was assessed using the specific situation for each province. The results showed that 1081.73 × 106 t of forestry waste could be produced in China, and 270.43 × 106 t (25% of the amount that could be collected) could be used to produce fuel ethanol. Assuming 10 t of sawdust could be converted into 1 t of ethanol, 27 × 106 t of ethanol could be produced from forestry waste. Different provinces have different potentials for producing ethanol from forestry waste, Guangdong Province, Guangxi Province, Sichuan Province, and Yunnan Province having higher potentials than the other provinces. It was predicted that 4478 × 106 t of fuel ethanol could be produced from woodcraft waste by 2020, and the provinces with the most potential were found to be Fujian Province, Heilongjiang Province, Jilin Province, Shanxi Province, Sichuan Province, Xinjiang Province, and Yunnan Province. Using forestry waste to produce ethanol could alleviate the energy shortage in China.

Expanding lysine industry: industrial biomanufacturing of lysine and its derivatives.

L-Lysine is widely used as a nutrition supplement in feed, food, and beverage industries as well as a chemical intermediate. At present, great efforts are made to further decrease the cost of lysine to make it more competitive in the markets. Furthermore, lysine also shows potential as a feedstock to produce other high-value chemicals for active pharmaceutical ingredients, drugs, or materials. In this review, the current biomanufacturing of lysine is first presented. Second, the production of novel derivatives from lysine is discussed. Some chemicals like L-pipecolic acid, cadaverine, and 5-aminovalerate already have been obtained at a lab scale. Others like 6-aminocaproic acid, valerolactam, and caprolactam could be produced through a biological and chemical coupling pathway or be synthesized by a hypothetical pathway. This review demonstrates an active and expansive lysine industry, and these green biomanufacturing strategies could also be applied to enhance the competitiveness of other amino acid industry.

Biochemical properties of GH94 cellodextrin phosphorylase THA_1941 from a thermophilic eubacterium Thermosipho africanus TCF52B with cellobiose phosphorylase activity.

A hypothetic gene (THA_1941) encoding a putative cellobiose phosphorylase (CBP) from Thermosipho africanus TCF52B has very low amino acid identities (less than 12%) to all known GH94 enzymes. This gene was cloned and over-expressed in Escherichia coli BL21(DE3). The recombinant protein was hypothesized to be a CBP enzyme and it showed an optimum temperature of 75 °C and an optimum pH of 7.5. Beyond its CBP activity, this enzyme can use cellobiose and long-chain cellodextrins with a degree of polymerization of greater than two as a glucose acceptor, releasing phosphate from glucose 1-phosphate. The catalytic efficiencies (k cat/K m) indicated that cellotetraose and cellopentaose were the best substrates for the phosphorolytic and reverse synthetic reactions, respectively. These results suggested that this enzyme was the first enzyme having both cellodextrin and cellobiose phosphorylases activities. Because it preferred cellobiose and cellodextrins to glucose in the synthetic direction, it was categorized as a cellodextrin phosphorylase (CDP). Due to its unique ability of the reverse synthetic reaction, this enzyme could be a potential catalyst for the synthesis of various oligosaccharides. The speculative function of this CDP in the carbohydrate metabolism of T. africanus TCF52B was also discussed.

Genome-wide gene expression patterns in dikaryon of the basidiomycete fungus Pleurotus ostreatus

Abstract Dikarya is a subkingdom of fungi that includes Ascomycota and Basidiomycota. The gene expression patterns of dikaryon are poorly understood. In this study, we bred a dikaryon DK13 × 3 by mating monokaryons MK13 and MK3, which were from the basidiospores of Pleurotus ostreatus TD300. Using RNA-Seq, we obtained the transcriptomes of the three strains. We found that the total transcript numbers in the transcriptomes of the three strains were all more than ten thousand, and the expression profile in DK13 × 3 was more similar to MK13 than MK3. However, the genes involved in macromolecule utilization, cellular material synthesis, stress-resistance and signal transduction were much more up-regulated in the dikaryon than its constituent monokaryons. All possible modes of differential gene expression, when compared to constituent monokaryons, including the presence/absence variation, and additivity/nonadditivity gene expression in the dikaryon may contribute to heterosis. By sequencing the urease gene poure sequences and mRNA sequences, we identified the monoallelic expression of the poure gene in the dikaryon, and its transcript was from the parental monokaryon MK13. Furthermore, we discovered RNA editing in the poure gene mRNA of the three strains. These results suggest that the gene expression patterns in dikaryons should be similar to that of diploids during vegetative growth.

Effects of Lactobacillus casei and Enterococcus faecalis on growth performance, immune function and gut microbiota of suckling piglets.

This study was carried out to investigate the effects of orally administrated Lactobacillus casei and Enterococcus faecalis on performance, immune function and gut microbiota of suckling piglets. Neonatal piglets (n = 120) were randomly assigned to 4 groups, with 30 suckling piglets in each group. The piglets were from 15 litters, one male and one female piglet were selected for each group in each litter. The Control group was administrated with normal saline, the other groups with L. casei or E. faecalis or a combination of L. casei and E. faecalis at a ratio of 3:1. Each piglet was orally administrated with 1, 2, 3 and 4 ml probiotics or normal saline at the age of 1, 7, 14 and 21 d, respectively. The piglets were weaned at the age of 21 d. The results showed that compared with the Control group, the average daily gain of piglets administrated with probiotics was significantly increased, and the diarrhoea rate and mortality were significantly decreased (p < 0.05). After supplementation of the combined probiotics, the protease activity in stomach, duodenum and colon was increased and in all supplemented groups, the immunoglobulin A concentration in plasma was significantly higher (p < 0.05). The combined probiotics significantly increased villus length and the expression level of transforming growth factor-ß in the jejunum (p < 0.05) but decreased the expression level of the jejunal tumour necrosis factor-α (p < 0.05). In addition, probiotics could regulate gut microbiota and increase microbial similarity coefficients for keeping piglet gut microbiota stable.

Genome-wide gene expression patterns in dikaryon of the basidiomycete fungus Pleurotus ostreatus.

Dikarya is a subkingdom of fungi that includes Ascomycota and Basidiomycota. The gene expression patterns of dikaryon are poorly understood. In this study, we bred a dikaryon DK13×3 by mating monokaryons MK13 and MK3, which were from the basidiospores of Pleurotus ostreatus TD300. Using RNA-Seq, we obtained the transcriptomes of the three strains. We found that the total transcript numbers in the transcriptomes of the three strains were all more than ten thousand, and the expression profile in DK13×3 was more similar to MK13 than MK3. However, the genes involved in macromolecule utilization, cellular material synthesis, stress-resistance and signal transduction were much more up-regulated in the dikaryon than its constituent monokaryons. All possible modes of differential gene expression, when compared to constituent monokaryons, including the presence/absence variation, and additivity/nonadditivity gene expression in the dikaryon may contribute to heterosis. By sequencing the urease gene poure sequences and mRNA sequences, we identified the monoallelic expression of the poure gene in the dikaryon, and its transcript was from the parental monokaryon MK13. Furthermore, we discovered RNA editing in the poure gene mRNA of the three strains. These results suggest that the gene expression patterns in dikaryons should be similar to that of diploids during vegetative growth.

Synthesis and swelling behaviors of carboxymethyl cellulose-based superabsorbent resin hybridized with graphene oxide.

Well-dispersed graphene oxide sheets were successfully incorporated into a superabsorbent resin through in situ graft polymerization of acrylic acid on carboxymethyl cellulose backbone in the presence of graphene oxide as filler. The structure and properties of the resultant superabsorbent resin were studied in detail by means of a variety of characterization methods. The influence of the feed ratio of starting materials (such as GO, initiator, cross-linker, the ratio of CMC to AA and the neutralized degree of AA) and pH values on water absorbency and retention ability was extensively determined and discussed. The obtained results showed that the introduction of graphene oxide had no obvious influence on the inherent structure of the superabsorbent resin but changed the surface morphology significantly. Importantly, the hybrid superabsorbent resin showed an enhanced thermal stability and remarkably improved swelling ratio as well as water-retention ability comparing with that of the pure superabsorbent resin.