Looking into the Market Behaviors through the Lens of Correlations and Eigenvalues: An Investigation on the Chinese and US Markets Using RMT.

This research systematically analyzes the behaviors of correlations among stock prices and the eigenvalues for correlation matrices by utilizing random matrix theory (RMT) for Chinese and US stock markets. Results suggest that most eigenvalues of both markets fall within the predicted distribution intervals by RMT, whereas some larger eigenvalues fall beyond the noises and carry market information. The largest eigenvalue represents the market and is a good indicator for averaged correlations. Further, the average largest eigenvalue shows similar movement with the index for both markets. The analysis demonstrates the fraction of eigenvalues falling beyond the predicted interval, pinpointing major market switching points. It has identified that the average of eigenvector components corresponds to the largest eigenvalue switch with the market itself. The investigation on the second largest eigenvalue and its eigenvector suggests that the Chinese market is dominated by four industries whereas the US market contains three leading industries. The study later investigates how it changes before and after a market crash, revealing that the two markets behave differently, and a major market structure change is observed in the Chinese market but not in the US market. The results shed new light on mining hidden information from stock market data.

Efficient production of the glycosylated derivatives of baicalein in engineered Escherichia coli.

Baicalein-7-O-glucoside and baicalein-7-O-rhamnoside have been proven to possess many pharmacological activities and are potential candidate drug leads and herb supplements. However, their further development is largely limited due to low content in host plants. Few studies reported that both bioactive plant components are prepared through the bioconversion of baicalein that is considered as the common biosynthetic precursor of both compounds. Herein, we constructed a series of the engineered whole-cell bioconversion systems in which the deletion of competitive genes and the introduction of exogenous UDP-glucose supply pathway, glucosyltransferase, rhamnosyltransferase, and the UDP-rhamnose synthesis pathway are made. Using these engineered strains, the precursor baicalein is able to be transformed into baicalein-7-O-glucoside and baicalein-7-O-rhamnoside, with high-titer production, respectively. The further optimization of fermentation conditions led to the final production of 568.8 mg/L and 877.0 mg/L for baicalein-7-O-glucoside and baicalein-7-O-rhamnoside, respectively. To the best of our knowledge, it is the highest production in preparation of baicalein-7-O-glucoside from baicalein so far, while the preparation of baicalein-7-O-rhamnoside is the first reported via bioconversion approach. Our study provides a reference for the industrial production of high-value products baicalein-7-O-glucoside and baicalein-7-O-rhamnoside using engineered E. coli. KEY POINTS: • Integrated design for improving the intracellular UDP-glucose pool • High production of rare baicalein glycosides in the engineered E. coli • Baicalein-7-O-glucoside and baicalein-7-O-rhamnoside.

Isolation of Bacillus sp. with high laccase activity for green biodecolorization of synthetic textile dyes.

New Bacillus sp. strains with spore-laccase activity were isolated from rotten wood and soil samples and were identified as Bacillus sp. FM-78 and Bacillus paramycoides FM-86 by 16S rDNA gene sequence analysis. Both laccases were stable at broad pH range and high temperature. The laccase of strain FM-78 showed preferable activity and stability, with no loss of activity after 7 days incubation at pH 9.0, and 20.36% of its initial activity obtained after 10 h at 80 °C. 1 mmol/L EDTA, NaN3 and SDS resulted in about 46-59% inactivation and strongly inhibition (87.88%) was caused by 1 mmol/L L-cysteine. However, the spore laccase could tolerate towards 0.5 mol/L NaCl as well as 10% of organic solvents. Reactive black 5, reactive blue 19 and crystal violet were decolorized by the spore laccase in the absence of mediator. The decolorization process was efficiently promoted with the presence of acetosyringone, and the color removal ratio was more than 80% in 1 h with the pH values of 6.6 or 9.0. Finally, the above unusual properties of Bacillus sp. spore laccase indicated it as a potential candidate in the dye decolorization in an ecofriendly and cost-effective way.

Efficient production of isoquercitin, icariin and icariside II by a novel thermostable α-l-rhamnosidase PodoRha from Paenibacillus odorifer with high α-1, 6-/α-1, 2- glycoside specificity.

Minor flavonoids, such as isoquercitin, icariin and icariside II, have desired bioactivity and bioavailability. To enhance the production efficiency on converting rutin and epimedin C into minor flavonoids, a novel GH family 78 α-l-rhamnosidase PodoRha from the Paenibacillus odorifer was cloned and heterologous over-expressed in E. coli BL21(DE3). PodoRha exhibited a high catalytic ability in cleaving outer α-1, 2-rhamnopyranosyl moieties of epimedin C and α-1, 6- rhamnopyranosyl of rutin. It displayed the highest activity at 45 °C and pH 6.5, and has great thermostability at 40 °C. Under the optimal transformation condition (40 °C, pH 6.5, 1 h incubation), 10 g/L of Rutin was 99.86% transformed into 6.95 g/L of isoquercitin by PodoRha with a crude productivity of 6.95 g·L-1·h-1; 1.964 g/L icariin was detected after the epimedin C of the total Epimedium flavonoids (10 g/L) were 99.98% converted by PodoRha. Moreover, by using a two-stage conversion system with a crude icariside II productivity of 2.081 g·L-1·h-1, 5 g/L epimedin C was 99.85% converted into 3.122 g/L of icariside II with 1 h incubation under pH 6.5 at 40 °C after addition of 5.5 U/mL PodoRha; then with 30 min incubation under pH 6.5 at 90 °C after addition of 0.8 U/mL IagBgl1.

Enhanced Enzymatic Hydrolysis and Structure Properties of Bamboo by Moderate Two-Step Pretreatment.

A moderate two-step pretreatment method was investigated to improve the enzymatic saccharification of bamboo residues. SEM and FTIR were employed to characterize the structure changes. Fed-batch enzymatic saccharification was performed to obtain high concentration of fermentable sugar. Bamboo was impregnated at low severity of conditions (room temperature, 2% H2SO4 or 2% NaOH, 48 h) to initially alter the structure of bamboo, and then further pretreated by steam explosion at 1.0 MPa for 6 min. The highest delignification of 51% and the highest enzymatic hydrolysis of 47.1% were reached at 2% NaOH impregnation followed by steam explosion. The changes in the structural characteristics showed beneficial effects on the enzymatic hydrolysis. When a mixer of cellulase (30 FPU) and ß-glucosidase (10 CBU) was further used, the maximum enzymatic hydrolysis of 78.9% and total glucose yield of 68.2% were obtained. The maximum sugar release from the holocellulose was 500 mg/g bamboo, approximately 83.3% conversion efficiency based on monomeric sugar recovery. With fed-batch saccharification, a final substrate loading of 30% brought 107.7 g/L glucose, 35.81 g/L xylose, and 7.82 g/L arabinose release, respectively. This study provided an effective strategy for potential utilization of bamboo residues.

Screening of Cucumber Fusarium Wilt Bio-Inhibitor: High Sporulation Trichoderma harzianum Mutant Cultured on Moso Bamboo Medium.

Cucumber fusarium wilt is a soil-borne disease which causes serious production decrease in cucumber cultivation world widely. Extensive using of chemical pesticides has caused serious environmental pollution and economic losses, therefore, it is particularly urgent to develop efficient, safe and pollution-free biopesticide. In this study, a mutant strain of Trichoderma harzianum cultivated in moso bamboo medium was proved to be an efficient bio-inhibitor of the disease. The mutant strain T. harzianum T334, was obtained by three microwave mutagenesis cycles with an irradiation power of 600 W and irradiation time of 40 s. In contrast to the original strain, the inhibition rate on cucumber fusarium wilt of the strain T334 increased from 63 to 78%. In this work, disk milling pretreatment of moso bamboo has shown significant beneficial effects on both biotransformation and sporulation of T334. Its sporulation reached 3.7 × 109 cfu/g in mushroom bags with 90% bamboo stem powder (pretreated by disk milli), 9.5% bamboo leaf powder and 0.5% wheat bran when the ratio of solid to liquid was 4:6, the inoculum amount was 10%, and the culture temperature was 28°C. These results provide an alternative bioinhibitor for the control of cucumber fusarium wilt, and a potential usage of moso bamboo in the production of microbial pesticide.

Characterization of a novel thermostable glucose-tolerant GH1 ß-glucosidase from the hyperthermophile Ignisphaera aggregans and its application in the efficient production of baohuoside I from icariin and total epimedium flavonoids.

The minor flavonoid baohuoside I from Herba epimedii has better bioactivities than its precursor compounds icariin and other major epimedium flavonoids. In this study, a novel ß-glucosidase gene (Igag_0940) was cloned and expressed to improve the conversion efficiency in the process of baohuoside I production. For the first time, the recombinant IagBgl1 was purified and then identified uniquely as a trimer in GH 1 family protein from Archaea. The maximum activity of recombinant IagBgl1 was exhibited at 95 °C, pH 6.5, and it retained more than 70% after incubation at 90 °C for 4 h. IagBgl1 had a high catalytic activity towards icariin with a Kcat/Km ratio of 488.19 mM-1·s-1. Under optimized conditions (65 °C, pH 6.5, 0.8 U/mL enzyme, and 90 min), 10 g/L icariin was transformed into 7.564 g/L baohuoside I with a molar conversion of 99.48%. Meanwhile, 2.434 g/L baohuoside I was obtained from 10 g/L total epimedium flavonoids by a two-step conversion system built with IagBgl1 and two other thermostable enzymes. This is the first report of enzymatic conversion for producing baohuoside I by thermostable enzymes.

Itaconic acid production from undetoxified enzymatic hydrolysate of bamboo residues using Aspergillus terreus.

Itaconic acid (IA) production by fermentation of undetoxified hydrolysate of bamboo residues by Aspergillus terreus was demonstrated. Monosaccharides were obtained by pretreatment and enzymatic hydrolysis of bamboo residues. A. terreus could not grow and synthesize IA in the hydrolysate. The buffer was confirmed to be an inhibitor, and was successfully replaced by deionized water as the suspension, to release equivalent sugar and eliminate the inhibition. Corn steep liquor significantly improved the adaptability of A. terreus to the hydrolysate at 2.0 g/L. The IA titer obtained (19.35 g/L IA) was the highest to be reported for IA production from lignocellulose without detoxification. Simultaneous saccharification and fermentation and fed-batch fermentation increased the titer to 22.43 g/L and 41.54 g/L, respectively. Meanwhile, economic assessment proved that bamboo residues were potential substrates for IA production with economic effectiveness.

Effects of Liquid Hot Water Combined with 1, 4-Butanediol on Chemical Composition and Structure of Moso Bamboo.

The effects of liquid hot water combined with 1, 4-butanediol (LHW-BDO) on the chemical composition and structure of moso bamboo were investigated. The structure changes of moso bamboo fibers were characterized by infrared spectroscopy, X-ray diffraction, and electronic scanning electron microscopy. The results showed that the delignification rates of 1, 4-butanediol (BDO) and LHW-BDO pretreatment methods were at the same level (91.42-93.08%). However, compared with BDO pretreatment, the cellulose content in solid residue after LHW-BDO pretreatment was increased by 17.06% with a recovery rate of 75.68%, while the hemicellulose removal rate increased by 115.33% and reached 50.34%. After LHW-BDO pretreatment, the intramolecular hydrogen bonds, intermolecular hydrogen bonds, methylene bonds, and aromatic ether bonds of the fibers were broken, which contributed to the depolymerization and separation of cellulose, hemicellulose, and lignin molecules. However, LHW-BDO pretreatment does not destroy the ß-glycoside bond which links the glucose molecule inside the fiber molecule, which was also beneficial to the separation of cellulose. In addition, the amorphous zone of bamboo fibers was destroyed by the above treatments, and the fiber structure of bamboo samples mostly exists in crystalline form. The crystallinity of bamboo pretreated with LHW-BDO was increased by 32.15%. It can be found by scanning electron microscopy that the surface of the pretreated bamboo samples showed uniformly distributed bubbly protuberance.

Cloning, overexpression and characterization of a thermostable ß-xylosidase from Thermotoga petrophila and cooperated transformation of ginsenoside extract to ginsenoside 20(S)-Rg3 with a ß-glucosidase.

A thermostable ß-xylosidase gene Tpexyl3 from Thermotoga petrophila DSM 13,995 was cloned and overexpressed by Escherichia coli. Recombinant Tpexyl3 was purified, and its molecular weight was approximately 86.7 kDa. Its optimal activity was exhibited at pH 6.0 and 90 °C. It had broad specificity to xylopyranosyl, arabinopyranosyl, arabinofuranosyl and glucopyranosyl moieties. The ß-xylosidase activity of the recombinant Tpexyl3 was 6.81 U/mL in the LB medium and 151.4 U/mL in a 7.5 L bio-reactor. It was applied to transform ginsenoside extract into the pharmacologically active minor ginsenoside 20(S)-Rg3, which was combined with thermostable ß-glucosidase Tpebgl3. After transforming under optimal condition, the 20 g/L of ginsenoside extract was transformed into 6.28 g/L of Rg3 within 90 min, with a corresponding molar conversion of 95.0% and Rg3 productivity of 1793.49 mg/L/h, respectively. This study is the highest report of a GH3 family glycosidase with arabinopyranosidase activity and also the first report on the high substrate concentration bioconversion of ginsenoside extract to ginsenoside 20(S)-Rg3 by using two thermostable glycosidases.

Citric Acid Production from Acorn Starch by Tannin Tolerance Mutant Aspergillus niger AA120.

In this study, acorn starch was investigated as a new material for fermenting production of citric acid by using a tannin tolerance mutant strain Aspergillus niger AA120. The mutant A. niger AA120 was obtained by initially atmospheric pressure plasma at room temperature (ARTP) mutagenesis and then tannin gradient domestication. ARTP experiments showed that a "double-saddle" shape of survival rate curve was achieved, and a positive mutation rate of 63.6% was reached by setting the implantation time of mutagenesis to 100 s. In contrast to the original stain at the presence of 20.0 g/L tannin in the medium, the selected mutant A. niger AA120 exhibits an increase of biomass by 43.76% to 32.9 g/L, and citric acid production capacity by 20.34% to 130.8 g/L, with 8% (w/w) of inoculation quantity, an initial pH of 6.2 and shaking speed of 250 r/min. In this work, we present a referable method for the mutagenesis screening of the A. niger, and the application of acorn starch as a new raw material for the development of the citric acid industry.

High-level expression of recombinant thermostable ß-glucosidase in Escherichia coli by regulating acetic acid.

In the fermentation progress, fermentation parameters including the feed rate, induction temperature, and induction pH evidently regulate the accumulation of acetic acid generated by recombinant E. coli in the medium. The production of thermostable ß-glucosidase (Tpebgl3) was increased by optimizing the parameters mentioned step by step. The optimal conditions were obtained with the highest enzyme expression (560.4U/mL) and the maximum DCW (65g/L) at the pre-induction specific growth rate of 0.2h-1 followed by a post-induction specific growth rate (0.18h-1); induction temperature is 39°C; the pH is 7.2; the concentration of acetic acid was maintained all along below 0.9g/L. Results show it is necessary for the synthesis of Tpebgl3 to regulate the accumulation of acetic acid at the premise of feeding to meet the normal growth of E. coli. The production of Tpebgl3 by recombinant E. coli is the highest reported to date.

Overexpression and characterization of a Ca(2+) activated thermostable ß-glucosidase with high ginsenoside Rb1 to ginsenoside 20(S)-Rg3 bioconversion productivity.

The thermostable ß-glucosidase gene from Thermotoga petrophila DSM 13995 was cloned and overexpressed in Escherichia coli. The activity of the recombinant ß-glucosidase was 21 U/mL in the LB medium. Recombinant ß-glucosidase was purified, and its molecular weight was approximately 81 kDa. The optimal activity was at pH 5.0 and 90 °C, and the thermostability of the enzyme was improved by Ca(2+). The ß-glucosidase had high selectivity for cleaving the outer and inner glucopyranosyl moieties at the C-20 carbon of ginsenoside Rb1, which produced the pharmacologically active minor ginsenoside 20(S)-Rg3. In a reaction at 90 °C and pH 5.0, 10 g/L of ginsenoside Rb1 was transformed into 6.93 g/L of Rg3 within 90 min, with a corresponding molar conversion of 97.9%, and Rg3 productivity of 4620 mg/L/h. This study is the first report of a GH3-family enzyme that used Ca(2+) to improve its thermostability, and it is the first report on the high substrate concentration bioconversion of ginsenoside Rb1 to ginsenoside 20(S)-Rg3 by using thermostable ß-glucosidase under high temperature.

Improvement of the optimum pH of Aspergillus niger xylanase towards an alkaline pH by site-directed mutagenesis.

In an attempt to shift the optimal pH of the xylanase B (XynB) from Aspergillus niger towards alkalinity, target mutation sites were selected by alignment between Aspergillus niger xylanase B and other xylanases that have alkalophilic pH optima that highlight charged residues in the eight-residues-longer loop in the alkalophilic xylanase. Multiple engineered XynB mutants were created by site-directed mutagenesis with substitutions Q164K and Q164K+D117N. The variant XynB-117 had the highest optimum pH (at 5.5), which corresponded to a basic 0.5 pH unit shift when compared with the wild-type enzyme. However, the optimal pH of the XynB- 164 mutation was not changed, similar to the wild type. These results suggest that the residues at positions 164 and 117 in the eight-residues-longer loop and the cleft's edge are important in determining the pH optima of XynB from Aspergillus niger.

Comparison of two laccases from Trametes versicolor for application in the decolorization of dyes.

It has been previously demonstrated that laccases exhibit great potential for use in several industrial and environmental applications. In this paper, two laccase isoenzyme genes, lccB and lccC, were cloned and expressed in Pichia pastoris GS115. The sequence analysis indicated that the lccB and lccC genes consisted of 1,563 and 1,584 bp, and their open reading frames encoded 520 and 527 amino acids, respectively. They had 72.7% degree of identity in nucleotides and 86.7% in amino acids. The expression levels of LccB and LccC were up to 32,479 and 34,231 U/l, respectively. The recombinant laccases were purified by ultrafiltration and (NH4)2SO4 precipitation, showing a single band on SDS-PAGE, which had a molecular mass of 58 kDa. The optimal pH and temperature for LccB were 2.0 and 55°C with 2,2'-azino-bis-[3-ethylbenzthiazolinesulfonic acid (ABTS) as a substrate, whereas LccC exhibited optimal pH and temperature at 3.0 and 60°C. The apparent kinetic parameters of LccB were 0.43 mM for ABTS with a Vmax value of 51.28 U/mg, and the Km and Vmax values for LccC were 0.29 mM and 62.89 U/mg. The recombinant laccases were able to decolorize five types of dyes. Acid Violet 43 (100 g/ml) was completely decolorized by LccB or LccC (2 U/ml), and the decolorization of Reactive Blue KN-R (100 g/ml) was 91.6% by LccC (2 U/ml). Thus, the study characterizes useful laccase isoenzymes from T. versicolor that have the capability of being incorporated into the treatment of similar azo and anthraquinone dyes from dyeing industries.

Enzymatic properties of Thermoanaerobacterium thermosaccharolyticum ß-glucosidase fused to Clostridium cellulovorans cellulose binding domain and its application in hydrolysis of microcrystalline cellulose.

BACKGROUND: The complete degradation of the cellulose requires the synergistic action of endo-ß-glucanase, exo-ß-glucanase, and ß-glucosidase. But endo-ß-glucanase and exo-ß-glucanase can be recovered by solid-liquid separation in cellulose hydrolysis by their cellulose binding domain (CBD), however, the ß-glucosidases cannot be recovered because of most ß-glucosidases without the CBD, so additional ß-glucosidases are necessary for the next cellulose degradation. This will increase the cost of cellulose degradation. RESULTS: The glucose-tolerant ß-glucosidase (BGL) from Thermoanaerobacterium thermosaccharolyticum DSM 571 was fused with cellulose binding domain (CBD) of Clostridium cellulovorans cellulosome anchoring protein by a peptide linker. The fusion enzyme (BGL-CBD) gene was overexpressed in Escherichia coli with the maximum ß-glucosidase activity of 17 U/mL. Recombinant BGL-CBD was purified by heat treatment and following by Ni-NTA affinity. The enzymatic characteristics of the BGL-CBD showed optimal activities at pH 6.0 and 65°C. The fusion of CBD structure enhanced the hydrolytic efficiency of the BGL-CBD against cellobiose, which displayed a 6-fold increase in Vmax/Km in comparison with the BGL. A gram of cellulose was found to absorb 643 U of the fusion enzyme (BGL-CBD) in pH 6.0 at 50°C for 25 min with a high immobilization efficiency of 90%. Using the BGL-CBD as the catalyst, the yield of glucose reached a maximum of 90% from 100 g/L cellobiose and the BGL-CBD could retain over 85% activity after five batches with the yield of glucose all above 70%. The performance of the BGL-CBD on microcrystalline cellulose was also studied. The yield of the glucose was increased from 47% to 58% by adding the BGL-CBD to the cellulase, instead of adding the Novozyme 188. CONCLUSIONS: The hydrolytic activity of BGL-CBD is greater than that of the Novozyme 188 in cellulose degradation. The article provides a prospect to decrease significantly the operational cost of the hydrolysis process.