Frontiers of Chemical Science and Engineering

ISSN 2095-0179

ISSN 2095-0187(Online)

CN 11-5981/TQ

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Strengthening mechanisms in carbon nanotube reinforced bioglass composites
Jing ZHANG, Chengchang JIA, Zhizhong JIA, Jillian LADEGARD, Yanhong GU, Junhui NIE
Front Chem Sci Eng. 2012, 6 (2): 126-131.

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Carbon nanotube reinforced bioglass composites have been successfully synthesized by two comparative sintering techniques, i.e., spark plasma sintering (SPS) and conventional compaction and sinteirng. The composites show improved mechanical properties, with SPS technique substantially better than conventional compact and sintering approach. Using SPS, compared with the 45S5Bioglass matrix, the maximum flexural strength and fracture toughness increased by 159% and 105%, respectively. Enhanced strength and toughness are attributed to the interfacial bonding and bridging effects between the carbon nanotubes and bioglass powders during crack propagations.

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Uptake and accumulation of multiwalled carbon nanotubes change the morphometric and biochemical characteristics of Onobrychis arenaria seedlings
Front Chem Sci Eng. 2012, 6 (2): 132-138.

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We have studied the effect of the engineered nanomaterial Taunit, containing multiwalled carbon nanotubes (MWCNTs), on the growth of Onobrychis arenaria seedlings and investigated whether affected plants uptake and accumulate MWCNTs. We found that 100 μg/mL and 1000 μg/mL of Taunit stimulated the growth of roots and stems, and enhanced the peroxidase activity in these parts of plants. Microscopy studies showed the presence of MWCNTs in the root and leaf tissues of seedlings exposed to Taunit, suggesting that MWCNTs have a capacity to penetrate the cell walls, accumulate in roots and translocate to the leaves. Thus the stimulating effect of MWCNTs on seedlings of O. arenaria may be associated with the primary uptake and accumulation of MWCNTs by plant roots followed by translocation to the other plant tissues.

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Direct ethanol production from rice straw by coculture with two high-performing fungi
Front Chem Sci Eng. 2012, 6 (2): 139-145.

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To develop efficient and economical direct ethanol production from fine rice straw crashed mechanically, two high-performing fungi, which can secret hyperactive cellulases and/or ferment effectively various sugars, were selected from some strains belong to Mucor circinelloides preserved in our laboratory. The simultaneous saccharification and fermentation (SSF) by coculture with these fungi was investigated. The screening of high-performing fungi resulted in the selection of NBRC 4572 as an ethanol-producing fungus and NBRC 5398 as a cellulase-secreting fungus. The strain 4572 produced ethanol aerobically from glucose and xylose in high yields of 0.420 g/g at 36 h and 0.478 g/g at 60 h, respectively, but secreted fairly low cellulases. On the other hand, the strain 5398 also produced ethanol from glucose in yield of 0.340 g/g though it had a little growth in xylose culture. However, it secreted hyperactive cellulases that are essential for hydrolysis of rice straw in culture and the maximum activities of endo-β-glucanase and β-glucosidase were 2.11 U/L and 1.47 U/L, respectively. In SSF of rice straw by coculture with two fungi selected, the ethanol production reached 1.28 g/L after 96 h when the inoculation ratio of the strain 5398 to the strain 4572 was 9.

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Biological pretreatment of corn stover by solid state fermentation of Phanerochaete chrysosporium
Jian ZHANG, Xin REN, Wenqun CHEN, Jie BAO
Front Chem Sci Eng. 2012, 6 (2): 146-151.

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Biological pretreatment is a promising way to overcome the biorecalcitrance of cleaving the supermolecular structure of lignocellulose by lignin degrading enzymes from microorganisms. Solid state fermentation of corn stover with the white-rot fungus Phanerochaete chrysosporium was carried out and the efficiency of this pretreatment was evaluated. The enzymatic hydrolysis yield reached a maximum when the corn stover was biologically pretreated for nine days, and the hydrolysis yield decreased sharply if the solid state fermentation was carried out for more than nine days. A possible explanation for this sharp decrease is that not only the lignin degrading enzymes (LiP and MnP) were secreted, but also other metabolites, which were toxic or fatal to the hydrolysis enzymes resulting in the lower hydrolysis yield were generated during the prolonged period of biopretreatment. These results are useful to help determine the optimal timing and to understand the lignin structure and degradation mechanism in biological pretreatment processes.

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The rpoS deficiency suppresses acetate accumulation in glucose-enriched culture of Escherichia coli under an aerobic condition
Prayoga SURYADARMA, Yoshihiro OJIMA, Yuto FUKUDA, Naohiro AKAMATSU, Masahito TAYA
Front Chem Sci Eng. 2012, 6 (2): 152-157.

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The role of Escherichiacoli rpoS on the central carbon metabolism was investigated through analyzing the deficiency of this regulon gene under aerobic and glucose-enriched culture conditions. The experimental results showed that while the wild type cells exhibited an overflow metabolism effect, the rpoS-deleting mutation alleviated this effect with the significant suppression of acetate accumulation under a high glucose condition. This gene deletion also induced the twofold upregulation of gltA and one-tenth downregulation of poxB, respectively. The overflow metabolism effect was confirmed to be recovered by re-introducing rpoS gene into the mutant. These results demonstrated rpoS changed the central carbon metabolism toward acetate overflow through dehydrogenation of pyruvate and reduction of TCA cycle activity.

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Effects of aroP gene disruption on L-tryptophan fermentation
Qian LIU, Yongsong CHENG, Qingyang XU, Xixian XIE, Ning CHEN
Front Chem Sci Eng. 2012, 6 (2): 158-162.

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The production of L-tryptophan through chemical synthesis, direct fermentation, bioconversion and enzymatic conversion has been reported. However, the role of the transport system for the aromatic amino acids in L-tryptophan producing strains has not been fully explored. In this study, the aroP gene of the L-tryptophan producing Escherichia coli TRTH strain was disrupted using Red recombination technology and an aroP mutant E. coli TRTH ΔaroP was constructed. Fed-batch fermentation of E. coli TRTH ΔaroP was carried out in 30-L fermentor to investigate the L-tryptophan production. Compared with E. coli TRTH, the aroP mutant was able to maintain a higher growth rate during the exponential phase of the fermentation and the L-tryptophan production increased by 13.3%.

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Screening of potential aquatic probiotics from the major microflora of guppies (Poecilia reticulata)
Front Chem Sci Eng. 2012, 6 (2): 163-173.

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The fish (Poecilia reticulata) was used as the source for probiotics. 46 bacterial isolates were obtained from the skin, gills, guts and intestines of the guppy, Poecilia reticulata (collected from a government model fish farm in Kottayam, India). Of the above isolated strains, four isolates were selected based on their inhibitory spectrum against five indicator strains, Aeromonas hydrophila 1739, Vibrio cholerae 3906, Flavobacterium 2495, Acinetobacter 1271 and Alcaligenes 1424 (standard cultures collected from Microbial Type Culture Collection (MTCC) Chandigarh, India). Among the resulting isolates, two were gram-positive cocci, namely MBTU-PB2 and MBTU-PB3 and belong to the genus Staphylococcus. The other two were gram-negative rods, namely MBTU-PB1 and MBTU-PB4, of the genera Enterobacter and Acinetobacter, respectively. The basic probiotic characteristics of these isolates such as the production of bacteriocin like inhibitory substances (BLIS), antibiotic sensitivities and growth profiles were also determined. The above four isolated strains exhibited different antagonisms than the five indicator strains. During incubation, the antibacterial activity gradually increased in the inhibition zone and was influenced by the lag period (λ) and doubling time. The lag periods for most of the four selected strains were shorter than those of the indicator strains and the isolates had different growth rates (μ) than the indicator strains. All four isolates produced BLIS, however, the strains had different BLIS activities against the indicator strains. Treatment of the neutralized cell free supernatants of the selected isolates with proteases eliminated or reduced the BLIS activity, suggesting a proteinaceous nature of the inhibitory compounds. Further, the optimum BLIS activity was observed at neutral pH after 18 h of incubation. The antibiotic sensitivity assay revealed that the isolates were susceptible to routinely used antibiotics, whereas the plasmid profiles showed that the plasmids had no role in the antagonistic properties of the four isolated strains. The results showed that the isolates could be a promising source for biocontrol agents in aquacultures.

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Evolutionary engineering of Phaffia rhodozyma for astaxanthin-overproducing strain
Jixian GONG, Nan DUAN, Xueming ZHAO
Front Chem Sci Eng. 2012, 6 (2): 174-178.

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Evolutionary engineering is a novel whole-genome wide engineering strategy inspired by natural evolution for strain improvement. Astaxanthin has been widely used in cosmetics, pharmaceutical and health care food due to its capability of quenching active oxygen. Strain improvement of Phaffia rhodozyma, one of the main sources for natural astaxanthin, is of commercial interest for astaxanthin production. In this study a selection procedure was developed for adaptive evolution of P. rhodozyma strains under endogenetic selective pressure induced by additive in environmental niches. Six agents, which can induce active oxygen in cells, were added to the culture medium respectively to produce selective pressure in process of evolution. The initial strain, P. rhodozyma AS2-1557, was mutagenized to acquire the initial strain population, which was then cultivated for 550 h at selective pressure and the culture was transferred every 48h. Finally, six evolved strains were selected after 150 generations of evolution. The evolved strains produced up to 48.2% more astaxanthin than the initial strain. Our procedure may provide a promising alternative for improvement of high-production strain.

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Mutagenesis and selective breeding of a high producing ?-poly-L-lysine strain
Tian WANG, Shiru JIA, Zhilei TAN, Yujie DAI, Shuai SONG, Guoliang WANG
Front Chem Sci Eng. 2012, 6 (2): 179-183.

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?-Poly-L-lysine (?-PL) is an L-lysine linear homopolymer, which is produced by bacteria belonging to the Streptomycetaceae family and by ergot fungi. However, the production of ?-PL by the wild bacteria strain is very low, which limits its utilization. In most bacteria including the Streptomyces genus, L-lysine is a precursor of ?-PL and is biosynthesized by the L-aspartate pathway. Aspartokinase (Ask) is the first key enzyme in this pathway and is subject to complex regulation such as the feedback inhibition by the end product amino acids. In addition, phosphoenolpyruvate carboxykinase is feedback-regulated by L-aspartate. To reduce these feedback inhibitions and to improve ?-PL productivity, resistant mutants were produced using sulfaguanidine (SG) + glycine+ L-lysine+ DL-3-hydroxynorvaline (AHV) as selective markers. Using the interaction between ?-PL and the charged dye in the solid culture medium, hundreds of colonies were simultaneously screened in a quick and effective manner. Finally, one ?-PL-producing strain, Streptomyces diastatochromogenes L9, was selected. The productivity of this strain during flask fermentation was 0.77 g/L, which was 15% higher than that of the original strain. Moreover, its fermentation performance and genetic characteristics were very stable.

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Preparation and characterization of asymmetric ultrafiltration membrane for effective recovery of proteases from surimi wash water
Nora’aini ALI, Fadhilati HASSAN, Sofiah HAMZAH
Front Chem Sci Eng. 2012, 6 (2): 184-191.

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The wash water generated from the surimi processing industry contains a large amount of proteases which are widely used in the food and biotechnology industries. Asymmetric polysulfone and polyethersulfone ultrafiltration (PSf-UF and PES-UF) membranes with three different polymer concentrations were screened for their abilities to recover proteases from surimi wash water. In-house fabricated membranes were prepared via a simple dry/wet phase inversion technique and were characterized in terms of permeability coefficient, membrane morphology and molecular weight cut-off (MWCO). The ability of the UF membranes to remove commercial proteases was tested at various pressures (up to 10 bars). The membrane with the best performance, 15 wt-% PSf-UF, was further tested with actual surimi wash water. The effect of the pH of the feed solution (4 to 8) in the pre-treatment stage was also evaluated to recover the highest amount of proteases. The highest retention of protease was 96% with a flux of 25.6 L/(m2·h) which was achieved with the 15 wt-% PSf-UF membrane.

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Mercury removal and recovery by immobilized Bacillus megaterium MB1
Meifang CHIEN, Ryo NAKAHATA, Tetsuya ONO, Keisuke MIYAUCHI, Ginro ENDO
Front Chem Sci Eng. 2012, 6 (2): 192-197.

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From several mercury removing microorganisms, we selected Bacillus megaterium MB1, which is non-pathogenic, broad-spectrum mercury resistant, mercuric ion reducing, heat tolerant, and spore-forming, as a useful bacterium for bioremediation of mercury pollution. In this study, mercury removal performance of the immobilized B. megaterium MB1 was investigated to develop safe, efficient and stable catalytic bio-agent for mercury bioremediation. The results showed that the alginate gel immobilized B. megaterium MB1 cells efficiently removed 80% of mercury from the solution containing 10 mg/L mercuric chloride within 24 h. These cells still had high activity of mercury removal even after mercuric ion loading was repeated for nine times. The analysis of mercury contents of the alginate beads with and without immobilized B. megaterium MB1 suggested that a large portion of reduced metallic mercury was trapped in the gel beads. It was concluded that the alginate gel immobilized B. megaterium MB1 cells have potential to remove and recover mercury from mercury-containing water.

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Biosorption of mercury and lead by aqueous Streptomyces VITSVK9 sp. isolated from marine sediments from the bay of Bengal, India
Front Chem Sci Eng. 2012, 6 (2): 198-202.

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Toxic heavy metals are increasingly accumulating in the environment worldwide and are considered to be life threatening contaminants. The biosorption of mercury and lead by marine actinomycetes isolated from marine sediment collected from the Bay of Bengal coast of Puducherry, India, was evaluated. The maximum tolerance concentration (MTC) of Streptomyces sp. was determined by a well diffusion method and a broth dilution method. The effects of the initial metal ion concentration, the pH and the biomass dosage on the biosorption of mercury and lead ions were investigated. The MTC of the isolate to metals was 200 mg·L-1 for mercury and 1800 mg·L-1 for lead. At neutral pH, the isolate had a maximum biosorption of metal ions of 200 mg·L-1 and 150 mg·L-1 for mercury and lead respectively. Fourier transform infrared (FTIR) absorption spectra showed the chemical interactions between the functional groups in the biomass such as hydroxyl (-OH), amine (-NH2), carboxyl (-COOH) and the metal ions. The isolate was further characterized by molecular taxonomy and identified as a member of the genus Streptomyces. Based on the phenotypic and phylogenetic analysis, the strain was classified as a new species of the genus Streptomyces and designated as Streptomyces VITSVK9 sp. (HM137310). A blast search of the 16S rDNA sequence of the strain showed the most similarity (95%) with Streptomyces sp. A515 Ydz-FQ (EU384279). Based on the results, it can be concluded that this marine Streptomyces could be used as a biosorbent for the removal of heavy metal ions from aqueous environments.

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Antifungal and antibacterial functions of medicinal leech recombinant destabilase-lysozyme and its heated-up derivative
Front Chem Sci Eng. 2012, 6 (2): 203-209.

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Antifungal activity of recombinant medicinal leech destabilase-lysozyme (rec.Dest-Lys) was investigated by using fungi: Botrytis cinerea, and Verticillium lateriticum, including yeasts Candida guillermoudii and Shizosaccharomyces pombe. Its antibacterial activity was investigated on gram-negative bacteria Pseudomonas fluorescens. These activities were assessed by radial agar diffusion assay, and scanning and transmission electron microscopy. Therefore, destabilase-lysozyme not only is endo-isopeptidase and lysozyme, but also has antifungal and antibacterial activities. Muramidase activity of rec.Dest-Lys disappeared after heat-treating at 90°C for 50 min without the loss of its antimicrobial activity. Furthermore we showed for the first time that the heated-up derivative of rec.Dest-Lys exhibited more potent activities against the above enumerated fungi and gram-negative bacteria than original protein.

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Optimization of pretreatment of Jatropha oil with high free fatty acids for biodiesel production
Front Chem Sci Eng. 2012, 6 (2): 210-215.

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A central composite rotatable design and response surface methodology were used in order to investigate the individual and combined effects of the ethanol-to-oil ratio, H2SO4 concentration, temperature and time of reaction on the reduction of free fatty acid (FFA) in jatropha oil. A quadratic polynomial model relating the reaction variables with FFA reduction was developed, presenting a good coefficient of determination (R2= 0.893). For reducing FFA to less than 1%, the optimal combination was found to be 0.62 v·v-1 ethanol-to-oil ratio (14.9 v·v-1 ethanol-to-FFA ratio), 1.7% v·v-1 H2SO4 concentration, and 79 min reaction time at a reaction temperature of 54°C. These results are of great relevance to maximize methyl esters formation by transesterification using an alkaline catalyst.

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Production of a polyclonal antibody to the VP26 nucleocapsid protein of white spot syndrome virus (wssv) and its use as a biosensor
Front Chem Sci Eng. 2012, 6 (2): 216-223.

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White spot syndrome virus (WSSV) is a major cause of high mortality in cultured shrimp all over the world. VP26 is one of the structural proteins of WSSV that is assumed to assist in recognizing its host and assists the viral nucleocapsid to move toward the nucleus of the host cell. The objective of this work was to produce a polyclonal antibody against VP26 and use it as a biosensor. The recombinant VP26 protein (rVP26) was produced in E. coli (BL21), purified and used for immunizing rabbits to obtain a polyclonal antibody. Western blot analysis confirmed that the antiserum had a specific immunoreactivity to the VP26 of WSSV. This VP26 antiserum was immobilized onto a gold electrode for use as the sensing surface to detect WSSV under a flow injection system. The impedance change in the presence of VP26 was monitored in real time. The sensitivity of the biosensor was in the linear range of 160–160000 copies of WSSV, indicating that it is good and sensitive for analysis of WSSV. The specificity of the biosensor was supported by the observation that no impedance change was detected even at high concentrations when using Yellow Head Virus (YHV). This biosensor may be applied to monitor the amount of WSSV in water during shrimp cultivation.

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Preparation of hemicellulolic oligosaccharides from Chamaecyparis obtuse (Hinoki) slurry using commercial enzymes
Yuya KUMAGAI, Hirokazu USUKI, Yukihiro YAMAMOTO, Akihiro YAMASATO, Takafumi MUKAIHARA, Tadashi HATANAKA
Front Chem Sci Eng. 2012, 6 (2): 224-231.

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Wood biomass is anticipated to serve as a substitute for carbon source, which has no feedstock competition with foods. Biomass is commonly used for the production of bio-ethanol by a series of processes such as pretreatment, enzymatic degradation, and fermentation. Hemicellulose, constituting 20 wt-% – 40 wt-% of biomass materials, contains various kinds of saccharides known to be bioactive substrates. Practical usage of hemicellulose is generally limited to its conversion to bio-ethanol. Here, we aimed to prepare hemicellulolic oligosaccharides, more valuable products other than ethanol. Therefore, the Hinoki slurry was treated with lime at room temperature for 3 h, and then neutralized with HCl. The resulting sample was treated with 13 types of commercial enzymes, and the saccharides produced in the supernatant were evaluated. The result showed that the commercial enzyme Cellulase SS (Nagase & Co., LTD.) effectively degraded the slurry to produce disaccharides and trisaccharides. Analysis of sugar components by liquid chromatography/mass spectrography (LC/MS) after the derivation with ethyl 4-aminobenzoate (ABEE) showed that mannobiose, mannotriose, and cellobiose were the major oligosaccharides. These results indicate valuable oligosaccharides can be successfully produced from Hinoki softwood slurry.

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Mechanisms of connective tissue formation and blocks of mitogen activated protein kinase
Front Chem Sci Eng. 2012, 6 (2): 232-237.

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Ninety male Wistar rats were selected under the “Guide for the Care and Use of Laboratory Animals” for skin-muscle wound models. Three groups of animals were examined respectively for inoculation of inhibitor of p38 MAPK (mitogen activated protein kinase) SB 203580 and JNK inhibitor SP 600125, and a control. Light microscopy, immunohistochemistry, and tensometry revealed that the inhibition of p38 or JNK cascades have modified the formation of the connective tissue scar. The degree of connective tissue growth in the area of surgical wound had been significantly reduced by the end of observation (30 d) as the SB 203580 was applied (% volume of collagen 43.60 (41.05 – 60.15) vs. 73.54 (66.87 – 78.01) in control, p = 0.002). Conversely, when we have applied the JNK blocker, the density of collagen in scar tissue increased (78.14 (72.77 – 81.14), p = 0.022 vs. control). SB203580 inhibits the expression of p38, c-Jun and c-Fos. When we have used the JNK blocker, the expression of c-Fos and c-Jun decreased, but the expression of p38 increased. This determines the high functional activity of fibroblasts after using SP 600125. Obtained results show the importance of studying regulators of cell differentiation as potential drugs, which significantly affect the outcome of the pathological processes.

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18 articles