Biochemical Engineering Journal (v.71, #C)
BEJ Keywords (II).
Editorial Board (CO2).
Two-stage oxygen supply strategy for enhanced lipase production by Bacillus subtilis based on metabolic flux analysis by Ping Song; Chen Chen; Qianqian Tian; Ming Lin; He Huang; Shuang Li (1-10).
► A detailed network model for Bacillus subtilis metabolism was constructed. ► Metabolic flux analysis (MFA) was used to investigate lipase production. ► Lipase production needs: high flux of tributyrin, TCA, and ATP; less biomass flux. ► TOS strategy was carried out with a 51% increase of lipase production based on MFA.Lipase production by Bacillus subtilis CICC20034 was assessed by metabolic flux distribution analysis. Lipase production was tested under various oxygen supply conditions in a synthetic medium to obtain the optimal oxygen supply profile. Based on the metabolic flux analysis, a two-stage oxygen supply strategy (TOS) that maintained high oxygen supply conditions during early fermentation phase, and then step-wisely reduced aeration to keep a stable, smooth, and adequate changing dissolved oxygen (DO) level profile throughout the production phases was carried out. With the proposed control strategy, the final lipase activity in batch fermentation significantly increased and reached a high level at 0.56 U/ml, corresponding to a 51% increase. The relevant metabolic flux analysis verified the effectiveness of the proposed control strategy. By applying TOS in composite medium, the final lipase activity reached 5.0 U/ml.
Keywords: Bacillus subtilis; Metabolic flux analysis; Lipase; Dissolved oxygen; Aeration; Fermentation;
Construction of a pilot plant for producing fine linen fibers for textiles by A.G. Valladares Juárez; G. Rost; U. Heitmann; E. Heger; R. Müller (11-18).
Display Omitted► A pilot plant for producing fine flax fibers with a new bioprocess was constructed. ► The plant was operated for one year and 140 kg of fine fibers were produced. ► The process is reliable, easy to scale-up and the equipment needed is simple. ► All process liquors could be reused several times producing high quality fibers. ► The new process avoids weather-related risks of traditional fiber production methods.A newly built 200-L-pilot plant was used for testing a novel chemo-enzymatic process for producing fine flax fibers without the weather-associated risks of dew retting. Raw, green and decorticated flax fibers were placed inside trays in the tempered main tank of the pilot plant, where a vertically acting mechanism gently moved the parallel fiber bundles. The fibers were incubated in an alkaline bath, in a pectinolytic culture of Geobacillus thermoglucosidasius PB94A and in a peroxide-softener bath. Finally the fibers were dried, combed and hackled into a sliver that is ready for wet-spinning of linen yarns. A total of 140 kg of raw fibers were treated in 40 different experiments in the pilot plant. The resolution of the raw fibers improved from 7.3 to 2.7 ± 0.3 after the treatment. The fineness was enhanced from 37.4 dtex to 11.1 ± 1.2 dtex. The proposed pilot-plant process produced constant-quality fibers and could be easily up-scaled.
Keywords: Flax; Retting; Pilot plant; Alkaline pectinases; Geobacillus thermoglucosidasius; Textiles;
Bacterial heavy metal transporter MerC increases mercury accumulation in Arabidopsis thaliana by Masako Kiyono; Yumiko Oka; Yuka Sone; Ryosuke Nakamura; Masa H. Sato; Kou Sakabe; Hidemitsu Pan-Hou (19-24).
► This study showed that transgenic MerC-SNARE plants may be useful for mercury phytoremediation. ► MerC is a bacterial heavy metal transporter and SNARE is used as an organelle-targeting marker to direct MerC to specific membranes. ► Transgenic plants were more resistant to mercury and accumulated more mercury. ► MerC can promote the transport and accumulation of mercury in transgenic plants.This study evaluated the feasibility of transgenic Arabidopsis engineered to express the bacterial heavy metal transporter MerC for the phytoremediation of mercury pollution. MerC, MerC–SYP121, or MerC–AtVAM3 proteins were found to be expressed in leaf segments of transgenic plants using an anti-MerC antibody immunostaining method. By sucrose density gradient centrifugation and immunoblotting analyses, MerC, MerC–SYP121, and MerC–AtVAM3 were found to localized in the Golgi apparatus, plasma membrane, and vacuole membrane, respectively. Transgenic Arabidopsis plants that expressed merC–SYP121 were more resistant to mercury and accumulated significantly more of this metal than wild-type Arabidopsis. These results demonstrated that expression of the bacterial heavy metal transporter MerC promoted the transport and accumulation of mercury in transgenic Arabidopsis, which may be a useful method for improving plants for the phytoremediation of mercury pollution.
Keywords: AtVAM3; Bacterial heavy metal transport; MerC; Mercury; Phytoremediation; SYP121;
Cholinium carboxylate ionic liquids for pretreatment of lignocellulosic materials to enhance subsequent enzymatic saccharification by Kazuaki Ninomiya; Takashi Yamauchi; Masafumi Kobayashi; Chiaki Ogino; Nobuaki Shimizu; Kenji Takahashi (25-29).
► Cholinium carboxylate ionic liquids (ILs) were used to pretreat lignocellulose. ► Especially, choline acetate ([Ch][OAc]) was found to be promising cholinium IL. ► [Ch][OAc] was compared with 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]). ► [Ch][OAc] was more biocompatible than [Emim][OAc]. ► [Ch][OAc] could pretreat lignocellulosic biomass as [Emim][OAc] did.The present study is the first report demonstrating that ionic liquids consisting of cholinium cations and linear carboxylate anions ([Ch][CA] ILs) can be used for pretreatment of lignocellulosic materials to enhance subsequent enzymatic saccharification. Six variants of [Ch][CA] ILs were systematically prepared by combining cholinium cations with linear monocarboxylate anions ([C n H2n+1–COO]−, n = 0–2) or dicarboxylate anions ([HOOC–C n H2n+1–COO]−, n = 0–2). These [Ch][CA] ILs were analyzed for their toxicity to yeast cell growth and their ability to pretreat kenaf powder for subsequent enzymatic saccharification. When assayed against yeast growth, the EC50 for choline acetate ([Ch][OAc]) was 510 mM, almost one order of magnitude higher than that for 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]). The cellulose saccharification ratio after pretreatment at 110 °C for 16 h with [Ch][OAc] (100.6%) was almost comparable with that after pretreatment with [Emim][OAc]. Therefore, [Ch][OAc] is a biocompatible alternative to [Emim][OAc] for lignocellulosic material pretreatment.
Keywords: Ionic liquid; Pretreatment; Lignin; Cellulose; Cellulase; Yeast;
Development of electrochemical sulfite biosensor based on SOX/PBNPs/PPY modified Au electrode by Rachna Rawal; C.S. Pundir (30-37).
► Development of sulfite biosensor based on SOX/PBNPs/PPY/Au electrode. ► Biosensor showed optimum response within 2 s, at 20 mV s−1, pH 8.0 and 30 °C. ► Linear range and detection limit were 0.5–1000 μM and 0.1 μM. ► Biosensor measured sulfite in red, rose and white wine samples. ► Electrode used 300 times over a period of 120 days when stored at 4 °C.A sulfite oxidase (SOX) (EC 126.96.36.199) purified from Syzygium cumini leaves was immobilized onto Prussian blue nanoparticles/polypyrrole (PBNPs/PPY) nanocomposite film electrodeposited onto the surface of gold (Au) electrode. An electrochemical sulfite biosensor was fabricated using SOX/PBNPs/PPY/Au electrode as working electrode, Ag/AgCl as standard electrode and Pt wire as auxiliary electrode connected through a potentiostat. The working electrode was characterized by Fourier Transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) at different stages of its construction. The biosensor showed optimum response within 2 s, when operated at 20 mV s−1 in 0.1 M Tris–HCl buffer, pH 8.0 and at 30 °C. Linear range and minimum detection limit were 0.5–1000 μM and 0.1 μM (S/N = 3) respectively. The sensor was evaluated with 95.0% recovery of added sulfite in red wine samples and 1.9% and 3.3% within and between batch coefficients of variation respectively. There was a good correlation (r = 0.96) between red wine samples sulfite value by standard DTNB method and the present method. The sensor was employed for determination of sulfite level in red, white and rose wine samples. The enzyme electrode was used 300 times over a period of 4 months, when stored at 4 °C.
Keywords: Sulfite; Sulfite biosensor; Prussian blue nanoparticles; Polypyrrole;
High cell density co-culture for production of recombinant hydrolases by M.R. Silva; M.G. Severo; P.S. Delabona; R. Ruller; J.G.C. Pradella; V.M. Gonçalves; S. Freitas (38-46).
► We showed that the concept of co-culture could be applied to produce more than one recombinant enzyme. ► We showed the successful application of high cell density cultivation to produce recombinant enzymes by co-culture. ► We developed a simple method to evaluate clone distribution during co-culture based on an enzymatic panel.Sugarcane bagasse is a residue with great potential as a feedstock for second-generation ethanol production. One of the approaches studied for making use of this material is the utilization of enzymes to hydrolyze the cell wall carbohydrates and generate fermentable sugars. These enzymes can be produced by cultivation of filamentous fungi or bacteria; however, the high production cost still represents a bottleneck to second-generation ethanol production. Expression of recombinant hydrolases through a co-culture strategy could be an interesting alternative for producing a recombinant cocktail at high levels of productivity that is tailor-made for each material to be hydrolyzed. In this study we evaluate the production of hydrolases by co-culturing two recombinant Escherichia coli, each expressing a specific hydrolase, β-1,3-1,4-glucanase or β-1,4-xylanase, both isolated from Bacillus subtilis. The cultures were conducted in bioreactors in batch and fed-batch mode in order to reach high cell densities. Co-culture in batch cultivation reached a dry cell weight of 10.4 g/L and volumetric activities of 31.96 U/mL and 11.89 U/mL for xylanase and endoglucanase, respectively. Fed-batch cultivation reached a dry cell weight of 60 g/L and the volumetric activities of xylanase and endoglucanase were respectively up to 5 and 1.3 times higher than those in batch mode. A competition assay indicates that no clone predominates over the other during cultivation. These results suggest that co-culture is a potential technique for producing recombinant hydrolase cocktails at lower cost than those associated with the production of a single culture.
Keywords: Co-culture; Escherichia coli; Recombinant cocktail; Hydrolases; Supplementation; High cell density;
Robust near-infra-red spectroscopic probe for dynamic monitoring of critical nutrient ratio in microbial fermentation processes by Sanjay Tiwari; G.K. Suraishkumar; Arun Chandavarkar (47-56).
► Optimal critical nutrient ratio (CNR) improves lipstatin yield from Streptomyces toxitricini. ► A near infra-red spectroscopy (NIRS) soft-probe for CNR was developed. ► High accuracy at atypically low concentrations indicates robustness of the probe. ► CNR probe is an alternative to expensive, arduous and hourly conventional analysis. ► The CNR probe was developed to improve bioprocess monitoring and control.Near infra-red spectroscopy (NIRS) measurements for bioprocess monitoring and control, are integral to process analytical technology (PAT) initiatives by EMEA and US-FDA. Yet, NIRS is not widely practiced in challenging microbial fermentation processes. We present a practical approach to develop NIRS models for linoleic acid (LA), oleic acid (OA) and ammonia which are critical nutrients in lipstatin fermentation by Streptomyces toxitricini. The lipstatin productivity was enhanced and steadied by dynamic monitoring and control of critical nutrient ratio (CNR) of LA to ammonia. The NIRS models were used to develop a novel, soft probe for CNR as an alternative to laborious, hourly, off-line analyses. The calibration was designed with typical data for four industrially useful microbes. The approach enabled direct use of spectra for a generally applicable model with distinct wave number optima of 6250–5555 cm−1 (LA), 6666–5882 cm−1 (OA), 6800–6300 cm−1 (ammonia). The standard errors of calibration and prediction were 1.5 × 10−3 g L−1, 1.6 × 10−3 g L−1, 1.1 ppm, and 8.9 × 10−4 g L−1, 1.8 × 10−2 g L−1, 3.6 ppm, respectively, for the respective nutrients. The robustness of probe is evident from the low mean percentage error of 2.3% for prediction of CNR at low concentration ranges of 0.02–0.24 g L−1 and 0.21–0.56 g g−1 for LA and CNR, respectively.
Keywords: Bioprocess monitoring; Control; Modeling; Fed-batch culture; Near infra-red spectroscopy; Critical nutrient ratio;
Electricity generation from dissolved organic matter in polluted lake water using a microbial fuel cell (MFC) by Yan-Rong He; Xiang Xiao; Wen-Wei Li; Pei-Jie Cai; Shi-Jie Yuan; Fang-Fang Yan; Meng-Xing He; Guo-Ping Sheng; Zhong-Hua Tong; Han-Qing Yu (57-61).
► MFC utilizes DOMs in lake water for electricity generation. ► Protein-like substances were substantially degraded by MFC treatment. ► Genotoxic agents in polluted lake water were almost completely removed. ► A potential pretreatment technology for sustainable remediation of lake water.A microbial fuel cell (MFC) was explored as a pretreatment method to remove dissolved organic matter (DOM) from polluted lake water and simultaneously generate electricity. After the MFC treatment, the total organic carbon concentration in the raw lake water was reduced by 50%, the physicochemical nature of DOMs was substantially altered. Protein-like substances in lake water were utilized as a major substrate for the MFC, while humic-like substances were refractory to the biodegradation. A further investigation into the bovine serum albumin utilization in an MFC confirms that the electricity generation was closely associated with the removal of protein-like substrates. Toxicity assessment by Salmonella typhimurium Sal94 indicates that the genotoxic agents in the polluted lake water were almost completely removed after the MFC treatment. This approach of coupling microbially-catalyzed electricity generation with DOM removal may offer a potential avenue for energy-efficient bioremediation of lake water.
Keywords: Lake water; Microbial fuel cell (MFC); Bioremediation; Biodegradation; Protein; Microbial growth;
Unstructured models for suspension cultures of Taxus media cells in a bioreactor under substrate-sufficient conditions by Chang-Yin Zhang; Yan-Shan Dong; Ya-Li Li; Chun-Hua Fu; Chun-Fang Zhao; Long-Jiang Yu (62-71).
► We study Taxus cell cultures in a bioreactor under substrate-sufficient conditions. ► We study the systematic kinetics of Taxus cell cultures in a bioreactor. ► We constitute kinetic unstructured models which incorporated energy spilling. ► Models include models of cell growth, biochemical reactions and rheology. ► We propose an optimized operation strategy of decreasing energy spilling.For a better understanding of the simulation, optimization, and process control in cell cultures, good kinetic models are necessary for large scale plant cell culture. In this paper, the systematic kinetics of taxol production by Taxus media cell suspension cultures in a stirred 15-L bioreactor under substrate-sufficient conditions and the absence of inducer intervention were studied. A kinetic model of cell growth was established by logistic equation, and kinetic unstructured models of substrate consumption, product synthesis and rheological behavior were constituted, which incorporated energy spilling. These models were verified by comparing the simulation results with those obtained experimentally. These results showed that energy spilling was a key factor that must be considered in constructing unstructured kinetic models of Taxus media cell suspension cultures in a stirred bioreactor under substrate-sufficient conditions. Besides, an optimized operation measure of decreasing energy spilling was proposed. An increase of 17.64% in cell biomass and 14.88% in taxol concentration were obtained when the strategy of limiting added carbon several times was experimentally implemented in a 15-L bioreactor. Results demonstrated that these established models should be helpful in the process prediction and operation optimization to guide the production and amplification of Taxus media cell suspension cultures in a bioreactor.
Keywords: Taxus media; Bioreactors; Large scale cultivation; Modeling; Kinetic parameters; Energy spilling;
Development of a structured dynamic model for the production of polyhydroxybutyrate (PHB) in Azohydromonas lata cultures by Christos Chatzidoukas; Giannis Penloglou; Costas Kiparissides (72-80).
► Dynamic model for the effect of culture conditions on the culture growth. ► Dynamic model for the effect of culture conditions on the PHB production mechanism. ► Transition from biomass-growth dominant phase to PHB-accumulation dominant phase. ► PHB inhibition effect on the biomass growth. ► Model-based scaling-up study of the PHB fermentative production in Azohydromonas lata cultures.The development of an accurate model representation of the fermentative production of polyhydroxybutyrate (PHB) is a prerequisite for the optimal operation and control of the microbial process. In the present work, a macroscopic model is developed to quantify the intracellular production of PHB in Azohydromonas lata bacteria. The proposed two-compartment structured model provides an accurate prediction of the metabolic and macroscopic phenomena occurring in A. lata bacterial cultures. Precisely, the proposed dynamic model accounts for biomass growth, polymer accumulation, carbon and nitrogen sources utilization and oxygen mass transfer rates. It is shown that the model can closely describe the time evolution of the bacterial culture via its direct comparison with experiments performed in flasks or/and a bioreactor. Moreover, it is shown that the model can be used as a simulation tool for process optimization and scaling-up studies of the PHB fermentative production in A. lata cultures.
Keywords: Biopolymers; Fermentation; Mathematical modelling; PHB; Structured macroscopic model; Scaling-up of bioprocesses;
Growth behavior of Aβ protofibrils on liposome membranes and their membrane perturbation effect by Toshinori Shimanouchi; Keiichi Nishiyama; Azusa Hiroiwa; Huong Thi Vu; Nachi Kitaura; Hiroshi Umakoshi; Ryoichi Kuboi (81-88).
The protofibrils of amyloid fibrils have recently drawn an attention due to their cytotoxicity although the physicochemical properties of the protofibrils as an intermediate of fibrillation process have still remained unclear. We investigated the growth behavior of the protofibrils of amyloid β protein with 40 amino acid residues in the presence of various liposomes and the membrane perturbation (calcein leakage). The growth behavior of protofibrils was apparently correlated with the protofibrils-induced calcein leakage. From the binding experiment using a hydrophobic fluorescence probe and the quartz crystal microbalance method combined with the planar lipid membrane, it is suggested that the apparent correlation between the growth behavior of protofibrils and their membrane perturbation resulted from the physicochemical properties of protofibrils such as hydrophobicity and the stability of hydrogen bonds. The protofibrils were found to show the highest hydrophobicity and the highest instability of hydrogen bonds of the proteins used in this study (monomer, protofibrils, matured fibrils, and other three typical proteins). It is anticipated that such properties of protofibrils were advantageous both for the binding of protofibrils with monomer (growth behavior) and for the binding of lipid bilayer membranes (membrane perturbation).
Keywords: Protofibril; Amyloid; Liposome; Hydrophobicity; Hydrogen bonds;
Kinetic model of lipase-catalyzed conversion of ascorbic acid and oleic acid to liposoluble vitamin C ester by Dejan Bezbradica; Marija Stojanović; Dušan Veličković; Aleksandra Dimitrijević; Milica Carević; Mladen Mihailović; Nenad Milosavić (89-96).
► Ping–pong model with ascorbic acid inhibition was obtained for ester synthesis. ► Kinetic study was performed at optimum values of reaction factors obtained by RSM. ► Model for whole reaction reach comprising ester hydrolysis term was developed. ► Dynamic simulation of the model fitted progress curve with high accuracy.The kinetics of l-ascorbyl oleate synthesis catalyzed by immobilized lipase from Candida antarctica in acetone was investigated. Significant inhibition of synthesis with an excess of ascorbic acid was observed. Experimental data were successfully fitted with a ping–pong bi–bi kinetic model with substrate inhibition, and related kinetic constants were determined. The kinetic study was performed at optimum experimental factors (temperature, initial water content, and enzyme concentration), which were determined using response surface methodology. Then, a model for predicting product–time progress curves was developed by expanding the obtained ping–pong model with terms describing ester hydrolysis. Kinetic constants of the reverse reaction were determined, and good congruence between the model and experimental data was achieved. Calculated kinetic constants revealed that lipase has the highest affinity for ascorbyl oleate, slightly lower activity with ascorbic acid, and the lowest activity with oleic acid. The obtained results are valuable for elucidating the reaction mechanism and represent an important contribution for reaction optimization and creating strategies to increase the productivity of vitamin C ester synthesis.
Keywords: Ascorbyl oleate; Lipase; Candida antarctica; Kinetic parameters; Substrate inhibition; Production kinetics;
An o-aminobenzoic acid film-based immunoelectrode for detection of the cardiac troponin T in human serum by Alessandra B. Mattos; Tatianny A. Freitas; Lauro T. Kubota; Rosa F. Dutra (97-104).
Display Omitted► An immunosensor based on polymer film was developed for cardiac troponin T (cTnT). ► Anti-cTnT was immobilized on o-aminobenzoic acid film. ► A detection limit of 16.0 pg mL−1 troponin T was achieved. ► It was analyzed the troponin T in human serum.An amperometric immunosensor for cardiac troponin T detection in human serum troponin T, a marker considered as “gold standard” for acute myocardial infarction diagnosis, is described. A stable carboxylic film to covalently bind antibodies against cTnT onto electrode surface was achieved with electropolymerization of the o-aminobenzoic acid. A fractional factorial study was performed to optimize the electropolymerization parameters. Cyclic voltammetry assays were carried out for characterize steps of the modified electrode surface. The obtained calibration curve at −0.05 V by amperometry presented a good linear response range from 0.05 to 5.0 ng mL−1 cTnT with a correlation coefficient of 0.992 (n = 6) and 0.016 ng mL−1 detection limit. The electrodes showed a good stability upon the analytical responses retaining 91.6% of its initial response after 18 days. This sensor showed outgoing results regarding sensitivity allowing reliable measurements of the cTnT at levels of clinical significance for acute myocardial infarctions diagnosis.
Keywords: Immunosensor; Poly(o-aminobenzoic acid); Acute myocardial infarction; Cardiac troponin T;
Efficient production of skimmin and 6′-succinylskimmin from umbelliferone by organic solvent-tolerant Bacillus licheniformis ZSP01 using nitrogen sources regulation strategy by Sen Zhang; Zhi Zhou; Zhong Yao; Bingfang He (105-110).
An efficient production of skimmin and a novel compound 6′-succinylskimmin, catalyzed by organic solvent-tolerant Bacillus licheniformis ZSP01, was successfully achieved using regulation strategy of nitrogen sources in media.Display Omitted► An organic solvent-tolerant bacteria Bacillus licheniformis ZSP01 was isolated. ► This is the first report on coumarin derivatives biotransformation by bacteria. ► One of the products 6′-succinylskimmin is a novel compound. ► Nitrogen sources regulation strategy was used to achieve efficient production. ► Cheap sugar donor was used and substrate specificity was investigated.An organic solvent-tolerant Bacillus licheniformis ZSP01 was newly isolated and utilized as a whole-cell biocatalyst for efficient production of skimmin and 6′-succinylskimmin from umbelliferone. Strikingly, the production of skimmin and 6′-succinylskimmin was significantly increased in the reaction media added with 10% dimethylsulfoxide (DMSO), and was separately regulated by adjusting the nitrogen sources in the fermentation medium. Efficient production of skimmin with a molar yield of 81% by resting cells of strain ZSP01 was achieved by using tryptone as nitrogen source for fermentation. Furthermore, efficient production of the novel compound, 6′-succinylskimmin, with a molar yield of 90% was obtained by using tryptone and yeast extract as a composite nitrogen source for fermentation. The glucosylation catalyzed by strain ZSP01 demonstrated an exquisite regioselectivity for a hydroxyl group at C-7 of the coumarin sheleton without neighboring substituents.
Keywords: Biocatalysis; Solvent-stable; Microbial growth; Optimization; Separation; Bacillus licheniformis;
Bioreactor leaching of uranium from a low grade Indian silicate ore by Abhilash; B.D. Pandey (111-117).
Display Omitted► This study for bioreactor leaching of uranium from silicate ore is the first attempt with such low tenor material. ► With bacterial species, 98.3% uranium is recovered in 14 days against 40 days in shake-flask. ► With bacteria and biogenic Fe(III), 87.6% uranium leaching is observed in 10 h at same conditions. ► Studies prove the worth of bioreactors in better mixing of slurry that improves the kinetics.Bio-leaching studies were carried out in a 2 L bioreactor- BIOSTAT-B® equipped with a PLC based controller at 20–40% (w/v) pulp density using enriched culture of A.ferrooxidans for Turamdih uranium ore (Jharkhand, India). With the enriched culture of A.ferrooxidans adapted on Fe(II) at pH 2.0, 35 °C and 20% (w/v) pulp density, a 98.3% uranium recovery was recorded in 14 days. The leaching of uranium in the bioreactor improved the dissolution rate by reducing the time from 40 days in shake flask as per our earlier studies to 14 days. While investigating the importance of biogenic Fe(III) in the bio-leaching process a maximum recovery of 84.7% U3O8 was observed at pH 2.0 and 20% (w/v) pulp density in 10 h as compared to the uranium leaching of 38.3% in the control experiments. On raising the pulp density to 30%, uranium bio-recovery increased to 87.6% in 10 h at pH 2.0 with <76 μm size material. This showed a distinct advantage because of better mixing of slurry in the bioreactor with auto-controlled conditions that improved the kinetics.
Keywords: Low-grade ore; Uranium; Mesophiles; Bioreactors; Fed-batch culture; Mixing; Biogenic Fe(III);
Effect of liposome membranes on disaggregation of amyloid β fibrils by dopamine by Huong Thi Vu; Toshinori Shimanouchi; Daisuke Ishikawa; Tadaharu Matsumoto; Hisashi Yagi; Yuji Goto; Hiroshi Umakoshi; Ryoichi Kuboi (118-126).
► The addition of liposome could accelerate the fibril disaggregation by catecholamine. ► Oxidized and negatively charged liposome showed the definite accelerated effect. ► Fibril disaggregation has relation with the bound water to liposome membranes.The inhibition of fibril formation of amyloid β (Aβ) and the disaggregation of Aβ fibrils are the promising approaches for a medical treatment of Alzheimer's disease (AD) therapy. In this study, we investigated the effects of liposomes on dopamine-induced disaggregation of Aβ fibrils by using the variety of liposomes. The used liposomes were normal liposomes, raft-forming liposomes, charged liposomes and oxidized liposomes. Those liposome could accelerate the disaggregation rate of fibrils. From the comparison of normal and charged liposomes, a certain contribution of dopamine via an electrostatic interaction to the disaggregation was confirmed. From raft-forming and oxidized liposomes, we revealed a significant contribution of bound water to liposomes, which could assist the formation of the quinine-form of dopamine by a removal of its proton. It is, therefore, concluded that the membrane surface of liposomes is considered to be an adequate environment for the dopamine-induced disaggregation of fibrils.
Keywords: Alzheimer's disease; Amyloid beta fibrils; Catecholamines; Liposome; Disaggregation;
Search for optimum conditions of wheat straw hemicelluloses cold alkaline extraction process by Juan C. García; M.J. Díaz; M.T. Garcia; M.J. Feria; D.M. Gómez; F. López (127-133).
► A method for the selective extraction of cold alkaline extraction. ► The method for extraction was optimized by using a 2 n factor. ► With this method allows 39.4% of all hemicellulose present in the raw material.A method for the selective extraction of hemicellulose from wheat straw involving cold alkaline extraction and subsequent separation by precipitation with ethanol is proposed. Wheat straw affords selective separation of the hemicellulose fraction from the cellulose and lignin fractions with the proposed method. The hemicellulose yield was optimized by using a 2n factor design to examine the influence of temperatures (temperature was designed between 20 and 40 °C), operation times (operation time was designed between 30 and 60 min) and alkali concentrations (alkali concentration was designed between 80 and 120 g L−1). These conditions allowed 56.1% of all hemicellulose initially present in the raw material, and 59.1% of the lignin, to be extracted. Subsequent separation of hemicellulose in the liquid phase from the cold alkaline extraction by precipitation with ethanol provided a fraction containing 39.4% of all hemicellulose (45.2% hemicellulose in extract/total extract) and only 12% of all lignin in the raw material.
Keywords: Wheat straw; Cold alkaline extraction; Hemicelluloses; Xylan;
Laccase production by newly isolated white rot fungus Funalia trogii: Effect of immobilization matrix on laccase production by Emre Birhanli; Selim Erdogan; Ozfer Yesilada; Yunus Onal (134-139).
► We prepared the low-cost activated adsorbents from apricot stone. ► The Cu–AC was firstly used for immobilization of pellets and for laccase production. ► The fungus immobilized on Cu–AC produced high levels of laccase. ► The crude laccase from immobilized culture decolorized the textile dyes.The laccase production performance of newly isolated Funalia trogii (F. trogii) immobilized on low-cost activated adsorbents prepared from apricot stone was investigated in inexpensive molasses medium and compared with free pellets. The adsorbents were apricot stone-based activated carbon (AC), Cu-impregnated apricot stone-based activated carbon (Cu–AC) and Fe-impregnated apricot stone-based activated carbon (Fe–AC). Cu–AC and Fe–AC were prepared by chemical activation. The values of BET surface area (S BET), total pore volume (V t), micropore surface area (S mic) and micropore volume (V mic) which show the pore properties of the activated carbons were 133 m2 g−1, 0.105 cm3 g−1, 108 m2 g−1 and 0.056 cm3 g−1 for Cu–AC and 145 m2 g−1, 0.112 cm3 g−1, 117 m2 g−1 and 0.061 cm3 g−1 for Fe–AC, respectively. F. trogii attached well on all of these adsorbents. However, the fungus immobilized on Cu–AC produced much higher levels of laccase than the others. The laccase activity obtained in 5 g L−1 molasses media after first cycle and mean laccase activity obtained after three cycles with fungus immobilized on Cu–AC were 29.23 U mL−1 and 27.04 U mL−1, respectively. These activities were only 0.25 and 0.39 U mL−1 with free pellets. The crude laccase from immobilized culture could also decolorize the textile dyes.
Keywords: Activated carbon; Enzymes; Enzyme production; Fermentation; Filamentous fungi; Laccase;