Optimization of critical medium components using response surface methodology for lipase production by Rhizopus delemar

The production process of a 1,3-position specific lipase from Rhizopus delemar was optimized by response surface methodology (RSM) and a Box–Behnken experimental design was used to study the interactive effects of fermentation medium components on lipase activity and microorganism growth. Preliminary batch tests were employed to obtain the favorable conditions for lipase activity analysis and found that sucrose, molasses, yeast extract, sunflower oil, tween-80 have significant influences on the lipase production and microorganism growth. The concentrations of five fermentation medium components were optimized. Among five variables, molasses sucrose and yeast extract were identified as less significant variables for lipase production. The optimum fermentation medium composition for lipase production by R. delemar was sucrose concentration 4.19 g/L, molasses sucrose 1.32 g/L, yeast extract 0.53 g/L, sunflower oil 1.11% (v/v), and tween-80 1.80% (v/v). In these conditions, the biomass concentration of 4.52 g/L with a lipolytic activity of 1585 μmol/L min was reached.     

Biocatalytic synthesis of short-chain flavor esters with high substrate loading by a whole-cell lipase from Aspergillus oryzae

A lipase from Aspergillus oryzae WZ007 exhibited high esterification activities toward a series of short-chain acids and alcohols. Moreover, it displayed a strong tolerance for high substrate concentration of up to 2.0 M and presented a highest initial rate of 276 mmol·L^− 1·h^− 1 at this concentration. After a reaction time of 48 h, the conversion rates of acids were higher than 80% for the synthesis of a majority of heptanoic acid esters, some octanoic acid esters and n-propyl hexanoate. These results implied that A. oryzae WZ007 lipase was a promising biocatalyst in the production of flavor esters.     

Optimizing endopectinase production from date pomace by Aspergillus niger PC5 using response surface methodology

In the first stage of experiments, a two-level fractional factorial design was used for screening of the most important factors among concentration of ammonium sulfate, potassium dihydrogen phosphate and date pomace, pH, total spore amount, aeration rate and fermentation time for the production of endopectinase from date pomace by Aspergillus niger PC5. Based on the results of first stage, ammonium sulfate (0.25–0.45%), pH (4.82–6.12) and fermentation time (50–90 h) were selected to be studied further. In the second stage, response surface methodology was used to determine the optimum fermentation conditions for production of the enzyme. Second stage results showed that, fermentation time was the most significant factor on endopectinase activity. After modeling of the fermentation process, maximum amounts of endopectinase (10.88 U ml^?1) predicted to be in the following fermentation conditions: pH of medium 5, ammonium sulfate concentration of 0.3% and fermentation time of 76.05 h.     

Optimization of pretreatment reaction for methyl ester production from chicken fat

In biodiesel production, to use low cost feedstock such as rendered animal fats may reduce the biodiesel cost. One of the low cost animal fats is the chicken fat for biodiesel production. It is extracted from feather meal which is prepared from chicken wastes such as chicken feathers, blood, offal and trims after rendering process. However, chicken fats often contain significant amounts of FFA which cannot be converted to biodiesel using an alkaline catalyst due to the formation of soap. Therefore, the FFA level should be reduced to desired level (below 1%) by using acid catalyst before transesterification. For this aim, sulfuric, hydrochloric and sulfamic (amidosulfonic) acids were used for pretreatment reactions and the variables affecting the FFA level including alcohol molar ratio, acid catalyst amount and reaction time were investigated by using the chicken fat with 13.45% FFA. The optimum pretreatment condition was found to be 20% sulfuric acid and 40:1 methanol molar ratio based on the amount of FFA in the chicken fat for 80 min at 60 °C. After transesterification, the methyl ester yield was 87.4% and the measured fuel properties of the chicken fat methyl ester met EN 14214 and ASTM D6751 biodiesel specifications.     

Antimicrobial activity of n-butyl lactate obtained via enzymatic esterification of lactic acid with n-butanol in supercritical trifluoromethane

The lipase-catalyzed synthesis of n-butyl lactate by esterification was performed in supercritical trifluoromethane. Immobilized lipase B from Candida antarctica (Novozym 435) was used as a biocatalyst. Process conditions (pressure and temperature) were optimized performing experiments in a high-pressure batch stirred-tank reactor. Experiments were carried out in the operative pressure ranges from 7.5 to 30 MPa and at temperatures 35 °C and 55 °C. For this purpose phase behavior for d,l-lactic acid/n-butanol/Novozym 435/supercritical fluid system at temperature 55 °C and different pressures was studied. The highest conversion of lactic acid after 26 h of reaction performance was obtained in supercritical trifluoromethane at 30 MPa and 55 °C.The n-butyl lactate (standard and enzymatically synthesized) and d,l-lactic acid were tested against four food-borne fungi: Saccharomyces cerevisiae, Aspergillus niger, Trichoderma viride and Penicillium cyclopium and three health-damaging bacteria: Escherichia coli, Pseudomonas fluorescens and Bacillus cereus by the agar well diffusion.     

High-pressure phase equilibrium data for the l-lactic acid + (propane + ethanol) and the l-lactic acid + (carbon dioxide + ethanol) systems

Biodegradable polymers have received increased attention due to their potential applications in the medicine and food industries; in particular, poly(l-lactic acid) (PLA) is of primary importance because of its biocompatibility and resorbable features. Recently, the synthesis of this biopolymer through the enzyme-catalyzed ring-opening polymerization of l-lactic acid in a compressed fluid has been considered promising. The aim of this work was to report the phase equilibrium data (cloud points) of the l-lactic acid + (propane + ethanol) and the l-lactic acid + (carbon dioxide + ethanol) systems. The phase equilibrium experiments were conducted in a variable-volume view cell employing the static synthetic method. These experiments were conducted in the temperature range of 323.15–353.15 K and at pressures up to 25 MPa; the mass ratio of ethanol to either CO₂ or propane was maintained at 1:9. The l-lactic acid + (propane + ethanol) system exhibited vapor–liquid, liquid–liquid and vapor–liquid–liquid transitions, whereas the l-lactic acid + (carbon dioxide + ethanol) system only exhibited liquid–liquid type transitions.     

Microwave-enhanced hydrolysis of poultry feather to produce amino acid

Poultry feather was hydrolyzed at relatively mild high temperature ranging from 433 to 473 K and autogenous pressure by intensification of microwave heating. The hydrolysate mainly contains arginine, alanine, threonine, glycine, praline, serine, glutamic acid, aspartic acid, cystine and tyrosine, which corresponds with hydrochloric acid catalytic hydrolysis. Based on the orthogonal experimental result, the total yield of amino acid attains about 54.72% with feather containing about 71.83% keratin at optimum reaction condition of temperature 473 K, time 20 min and weight ratio of water/feather 37.5. The high yield of amino acid and high efficiency of hydrolysis indicate that the microwave has better intensification on hydrolysis comparing with traditional strong acid catalytic or sub-critical hydrolysis. The apparent activation energies (E_a) are 85.12 and 63.00 kJ/mol as to the hydrolysis of feather and the degradation of produced amino acid with consecutive pseudo-first-order reaction kinetic model, and the great decrease of the values comparing with non-microwave heating should be the reason of the enhanced effect of microwave.     

Enzymatic synthesis of sugar fatty acid esters in organic solvent and in supercritical carbon dioxide and their antimicrobial activity

Lipase-catalyzed synthesis of different sugar fatty acid esters was performed in high yields in 2-methyl-2-butanol at atmospheric pressure and in supercritical carbon dioxide (SC CO₂) at 10 MPa. Influence of molecular sieves concentration on conversion in SC CO₂ was studied. Growth inhibitory effect of commercial sucrose fatty acid esters and enzymatically synthesized sucrose and fructose fatty acid esters on Gram-positive and Gram-negative micro-organisms, as well as on yeast was tested. Sucrose laurate inhibited the growth of Bacillus cereus food poisoning bacteria at a concentration of 9.375 mg/ml.     

Aircraft-based operation of an aerosol mass spectrometer: Measurements of tropospheric aerosol composition

The Aerodyne quadrupole aerosol mass spectrometer was deployed on the Falcon twin jet research aircraft operated by Deutsches Zentrum für Luft- und Raumfahrt (DLR). This was the first deployment of an AMS in a jet aircraft. Aerosol mass concentration measurements in the troposphere up to altitudes of about 11 km were performed within two measurement flights on 12 and 14 May 2003 over southern Germany. Background aerosol data were gained up to 6 km, while aircraft exhaust aerosol was be sampled at higher altitudes on 14 May, indicating the presence of sulfuric acid and unburned hydrocarbons in the exhaust particles. The boundary layer aerosol on 12 May was found to be composed of 49% organics, 12% sulfate, 15% ammonium, and 24% nitrate by mass. The upper edge of the boundary layer was marked by a sharp decrease of nitrate and ammonium at an altitude of 3 km, while sulfate and organics decreased to a much lesser degree. On 14 May, the boundary layer aerosol was composed of 23% organics, 20% sulfate, 24% ammonium, and 33% nitrate by mass, and the boundary layer reached up to about 5000 m and had no sharp upper edge. The size distributions indicated internal mixtures of ammonium sulfate and –nitrate in the boundary layer, while the organics were externally mixed. Additionally, a smaller mode consisting only of ammonium sulfate, was detected. This bimodal structure of ammonium sulfate was also detected above the boundary layer in 6 km altitude on 14 May.     

Comparison of red,brown and green seaweeds on enzymatic saccharification process

The production of bioethanol from seaweeds using acid hydrolysis and the enzymatic saccharification was studied. Red seaweed (Gelidium amansii), brown seaweed (Laminaria japonica), and green seaweed (Codium fragile) were selected, and the characteristics of their conversion to bioethanol were analyzed. The optimum conditions of the dilute acid hydrolysis preprocessing for bioethanol production from the seaweed were a reaction temperature of 150 °C, sulfuric acid content of 5.0 wt.%, and reaction time of 60 min. The seaweeds listed in order of bioethanol conversion performance are red seaweed > brown seaweed > green seaweed. The optimum dosage of enzyme was 2.0 mL per 10 g of seaweed. The optimal fermentation conditions for bioethanol production using seaweed included a commercial yeast dosage of 30 wt.% and a fermentation time of 3 days.     

Three phase partitioning coupled with ultrasound for the extraction of ursolic acid and oleanolic acid from Ocimum sanctum

In this study, three phase partitioning (TPP) is coupled with ultrasound for the extraction of ursolic acid (UA) and oleanolic acid (OA) from Ocimum sanctum leaves and process has been optimized to obtain maximum recovery. TPP is a relatively novel bioseparation technique used for the extraction, concentration and purification of enzymes and natural products. The technique of TPP was explored for the extraction of ursolic acid (UA) and oleanolic acid (OA) from O. sanctum leaves. The influence of various process parameters (pH, ammonium sulfate saturation, crude extract to t-butanol ratio, time and feed loading) on the extraction efficiency was investigated to get highest yield. The optimized conditions were found to be as follows: time – 120 min, pH – 7, ammonium sulfate saturation – 50% w/v, crude extract to t-butanol ratio – 1:1 and feed loading – 7.5% w/v. The highest yield obtained for UA and OA was 79.48% and 80.67% respectively under optimized conditions of TPP. Compared with TPP higher yield (83.36% and 85.58%) was obtained by ultrasound assisted TPP (UATPP) at 40 kHz and 180 W power and the time required was only 14 min as compared to 120 min of TPP. The extraction yield obtained was also compared with conventional solvent extraction and TPP-ultrasound was found to be an attractive technique for the extraction of UA and OA from O. sanctum leaves.     

A practical and efficient synthesis of quinoxaline derivatives catalyzed by task-specific ionic liquid

A cheap and recyclable task-specific ionic liquid N, N, N-trimethyl-N-propanesulfic acid ammonium hydrogen sulfate [TMPSA] · HSO₄ was used as the catalyst for the synthesis of quinoxaline derivatives. The reaction could be accomplished in water as well as organic solvent, and the satisfactory results were obtained under the mild conditions. The products could be separated from the catalyst simply by filtration and the catalyst could be recycled and reused for several times without noticeably decreasing the catalytic activity.     

High-performance supercapacitor of manganese oxide/reduced graphene oxide nanocomposite coated on flexible carbon fiber paper

Although supercapacitors have higher power density than batteries, they are still limited by low energy density and low capacity retention. Here we report a high-performance supercapacitor electrode of manganese oxide/reduced graphene oxide nanocomposite coated on flexible carbon fiber paper (MnO₂–rGO/CFP). MnO₂–rGO nanocomposite was produced using a colloidal mixing of rGO nanosheets and 1.8 ± 0.2 nm MnO₂ nanoparticles. MnO₂–rGO nanocomposite was coated on CFP using a spray-coating technique. MnO₂–rGO/CFP exhibited ultrahigh specific capacitance and stability. The specific capacitance of MnO₂–rGO/CFP determined by a galvanostatic charge–discharge method at 0.1 A g⁻¹ is about 393 F g⁻¹, which is 1.6-, 2.2-, 2.5-, and 7.4-fold higher than those of MnO₂–GO/CFP, MnO₂/CFP, rGO/CFP, and GO/CFP, respectively. The capacity retention of MnO₂–rGO/CFP is over 98.5% of the original capacitance after 2000 cycles. This electrode has comparatively 6%, 11%, 13%, and 18% higher stability than MnO₂–GO/CFP, MnO₂/CFP, rGO/CFP, and GO/CFP, respectively. It is believed that the ultrahigh performance of MnO₂–rGO/CFP is possibly due to high conductivity of rGO, high active surface area of tiny MnO₂, and high porosity between each MnO₂–rGO nanosheet coated on porous CFP. An as-fabricated all-solid-state prototype MnO₂–rGO/CFP supercapacitor (2 × 14 cm) can spin up a 3 V motor for about 6 min.     

Design of ionic liquid 1,3-disulfonic acid imidazolium hydrogen sulfate as a dual-catalyst for the one-pot multi-component synthesis of 1,2,4,5-tetrasubstituted imidazoles

Novel ionic liquid 1,3-disulfonic acid imidazolium hydrogen sulfate {[Dsim]HSO₄} efficiently catalyzes the synthesis of 1,2,4,5-tetrasubstituted imidazoles via the one-pot multi-component condensation of benzyl with aldehydes, primary amines and ammonium acetate at 90 °C under solvent-free conditions. Dual hydrogen-bond donors can be used to direct the assembly of this catalyst and the efficiency of it.     

Effect of TS-1 treatment by tetrapropyl ammonium hydroxide on cyclohexanone ammoximation

TS-1 has been treated with different concentrations of tetrapropyl ammonium hydroxide (TPAOH), characterized by a series of techniques, and studied in cyclohexanone ammoximation. The results show that the MFI structure of TS-1 is not destroyed, while mesopores are formed in TS-1 crystals and the pore diameters increase with the TPAOH concentrations; the amount of the framework Ti species decreases slightly at low concentrations of TPAOH, but decreases appreciably at the concentrations of TPAOH above 0.0125 mol/L; the activity and the selectivity of TS-1 are not affected by the treatment, but the catalyst stability is markedly increased after the TPAOH treatment. The increase of the stability is attributed to the mesopore formation. But when the pore diameters are larger than 6.51 nm, the catalyst stability begins decreasing due to the appreciable damage of the framework titanium by TPAOH.     

Biodiesel production from waste tallow

In the present investigation an attempt has been made to use waste tallow as low cost sustainable potential feed stock for biodiesel production. Effect of various process parameters such as amount of catalyst, temperature and time on biodiesel production was investigated. The optimal conditions for processing 5 g of tallow were: temperature, 50 and 60 °C; oil/methanol molar ratio 1:30 and 1:30, amount of H₂SO_4, 1.25 and 2.5 g for chicken and mutton tallow, respectively. Under optimal conditions, chicken and mutton fat methyl esters formation of 99.01 ± 0.71% and 93.21 ± 5.07%, was obtained after 24 h in the presence of acid. The evaluation of transesterification process was followed by gas chromatographic analysis of tallow fatty acid esters. A total of 98.29% and 97.25% fatty acids were identified in chicken and mutton fats, respectively. Both fats were found highly suitable to produce biodiesel with recommended fuel properties.     

Effect of Temperature on Phase and Alumina Extraction Efficiency of the Product from Sintering Coal Fly Ash with Ammonium Sulfate

A new developed technology for extracting alumina from coal fly ash was studied in this paper. In this technology, coal fly ash is first sintered with ammonium sulfate, forming ammonium aluminum sulfate in the resultant product, where alumina can be easily leached without using any strong acid or alkali. The products obtained under different sintering conditions were characterized by X-ray diffractometry. Alumina extraction efficiency of these products was also investigated. The results show that the sintering temperature and time substantially influence the phase composition and alumina extraction efficiency of sintered products, while the heating rate has little influence. The optimal sintering condition is 400 °C for 3 h in air with a heating rate of 6 °C·min^− 1. Under the optimal sintering condition, the alumina extraction efficiency from as-sintered coal fly ash can reach 85% or more.     

Fabrication and application of silicalite-1 and TS-1 hollow fibers with polyethylene imine (PEI) fibers as substrates

Silicalite-1 and titanium containing silicalite-1 (TS-1) hollow fibers were fabricated with polyethylene imine (PEI) fibers as substrates. The acid treated PEI fibers were positively charged and can be effectively coated with silicalite-1 or TS-1 nanocrystals from their colloidal solution. The adsorbed silicalite-1 or TS-1 nanocrystals grew up and became more compact upon two days of vapor phase Ostwald ripening in autoclave. Silicalite-1 and TS-1 hollow fibers were obtained after calcination at 400 °C in air. The shell thickness of the hollow fibers is ～1 μm. Hydroxylation of phenol with H₂O₂ was investigated over TS-1 based catalysts in order to compare influences of nanocrystals composed macrostructure and Al₂O₃ binder on the catalytic activities.     

Mixed micelles from methoxy poly(ethylene glycol)–polylactide and methoxy poly(ethylene glycol)–poly(sebacic anhydride) copolymers as drug carriers

mPEG–PLLA (poly l-lactic acid) is synthesized by ring-opening polymerization of lactide and conjugation with mPEG. Sebacic acid is modified with acetic anhydride and condensed with mPEG to form mPEG–PSA (poly sebacic anhydride). The micelles formed by mPEG–PLLA are characterized by slow degradation and low drug encapsulation efficiency; on the contrary, mPEG–PSA micelles are characterized by rapid degradation but high encapsulation efficiency. They can merge into spherical micelles (Φ = 140 nm) by self-assembly in water. The mixed micelles can successfully encapsulate a typical hydrophobic drug (curcumin), and significantly improve its solubility. Experimental results show that the mixed micelles have the features of high encapsulation efficiency and slow degradation.     

Production of Medium-Chain-Length Poly(3-hydroxyalkanoates) from Crude Fatty Acids Mixture by Pseudomonas putida

Microbial production of medium-chain-length poly(3-hydroxyalkanoates), PHA_MCL from crude fatty acids mixture was investigated. With ammonium as the growth limiting substrate, fatty acids mixture from saponified palm kernel oil (SPKO) supports good growth and PHA_MCL production of Pseudomonas putida PGA1. Growth of this microorganism on ammonium exhibited substrate inhibition kinetics which can be described using Andrews model with the substrate inhibition constant, K_i = 1.2 g L⁻¹. Concentration of SPKO in the aqueous medium should be at 10 g L⁻¹ or less, as higher concentrations can significantly reduced the volumetric oxygen transfer coefficient (K_La), biomass growth and PHA_MCL production. Uptake of SPKO by the organism follows a zero-order kinetics, indicating a mass transfer limitation of the free fatty acids by the P. putida PGA1 cells. In batch and fed-batch fermentations, PHA_MCL accumulation is encouraged under ammonium-limited condition with SPKO as the sole carbon and energy source. The amount of PHA_MCL accumulated and its specific production rate, q_PHA were influenced by the residual ammonium concentration level in the culture medium. It was observed that in both fermentation modes, when the residual ammonium becomes exhausted (<0.05 g L⁻¹), the PHA_MCL accumulation and q_PHA were significantly reduced. However, this effect can be reversed by feeding low amount of ammonium to the culture, resulting in significantly improved PHA_MCL yield and productivity. It is concluded that the feeding of residual ammonium concentration in the culture medium during the PHA_MCL accumulation has a positive effect on sustaining the PHA_MCL biosynthetic capability of the organism.