Wangliang Li

In situ magnetic separation and immobilization of dibenzothiophene-desulfurizing bacteria

In situ cell separation and immobilization of bacterial cells for biodesulfurization were developed by using superparamagnetic Fe(3)O(4) nanoparticles (NPs). The Fe(3)O(4) NPs were synthesized by coprecipitation followed by modification with ammonium oleate. The surface-modified NPs were monodispersed and the particle size was about 13 nm with 50.8 emu/g saturation magnetization. After adding the magnetic fluids to the culture broth, Rhodococcus erythropolis LSSE8-1 cells were immobilized by adsorption and then separated with an externally magnetic field. The maximum amount of cell mass adsorbed was about 530 g dry cell weight/g particles to LSSE8-1 cells. Analysis showed that the nanoparticles were strongly absorbed to the surface and coated the cells. Compared to free cells, the coated cells not only had the same desulfurizing activity but could also be easily separated from fermentation broth by magnetic force. Based on the adsorption isotherms and Zeta potential analysis, it was believed that oleate-modified Fe(3)O(4) NPs adsorbed bacterial cells mainly because of the nano-size effect and hydrophobic interaction.

Partitioning Behavior of Penicillin G in Aqueous Two Phase System Formed by Ionic Liquids and Phosphate

Abstract An aqueous two‐phase system (ATPS) was presented with hydrophilic ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl) and NaH2PO4 aqueous solution in this paper. The partitioning behavior of penicillin G in the ATPS was investigated. Concentrations of NaH2PO4, penicillin G, and [Bmim]Cl were evaluated to determine their effects on the partition coefficient and extraction yield of penicillin G. It was found that both of partition coefficient and extraction yield strongly depended on the concentration of [Bmim]Cl, penicillin and NaH2PO4. A high extraction yield of 93% was achieved with the following parameters: NaH2PO4 · 2H2O 40% (wt%), penicillin 45000∼50000 u/ml, [Bmim]Cl 20∼21% (wt%). The [Bmim]Cl/NaH2PO4 system was also applied in a real filtration of penicillin G fermentation broth and the extraction yield was averaged at 91.5%. It is worthy noting that the working pH value of ATPS was at the range of 5∼6, no emulsification and protein denaturation could be observed.

Efficient conversion of crop stalk wastes into succinic acid production by Actinobacillus succinogenes

Succinic acid is valued as a key platform chemical for use in a variety of synthetic applications. Efficient biosynthesis of succinic acid from renewable biomass resource is reported in this paper. Batch fermentations were carried out to analyze influence of several carbon sources on succinic acid production from feedstock wastes by Actinobacillus succinogenes BE-1. Crop stalk wastes, including corn stalk and cotton stalk, were enzymatically converted into a carbohydrate-rich feedstock, obtaining glucose concentrations approaching 65-80% of the total reducing sugar. For the anaerobic batch cultivation with cotton stalk hydrolysates, the production of succinic acid was 15.8 g l(-1) with a high yield of 1.23 g per g glucose. Glucose and xylose were utilized at same time, while cellubiose was not consumed until glucose and xylose were completely consumed.

High-concentration sugars production from corn stover based on combined pretreatments and fed-batch process.

In this paper, high-concentration sugars were produced from pretreated corn stover. The raw corn stover was pretreated in a process combining steam explosion and alkaline hydrogen-peroxide. The hemicellulose and lignin were removed greatly. The cellulose content increased to 73.2%. Fed-batch enzymatic hydrolysis was initiated with 12% (w/v) solids loading and 20 FPU/g solids. Then, 6% solids were fed consecutively at 12, 36 and 60 h. After 144 h, the final concentrations of reducing sugar, glucose, cellobiose and xylose reached 220, 175, 22 and 20 g/L, respectively. The final total biomass conversion was 60% in fed-batch process.

Reduction of hexavalent chromium by Pannonibacter phragmitetus LSSE-09 stimulated with external electron donors under alkaline conditions.

A novel Cr (VI) resistant bacterial strain LSSE-09, identified as Pannonibacter phragmitetus, was isolated from industrial sludge. It has strong aerobic and anaerobic Cr (VI)-reduction potential under alkaline conditions. At 37 °C and pH 9.0, growing cells of strain LSSE-09 could completely reduce 100 and 1000 mg L(-1) Cr (VI)-Cr (III) within 9 and 24h, respectively under aerobic condition. Resting cells showed higher anaerobic reduction potential with the rate of 1.46 mg g(-1)((dry weight))min(-1), comparing with their aerobic reduction rate, 0.21 mg g(-1)min(-1). External electron donors, such as lactate, acetate, formate, pyruvate, citrate and glucose could highly increase the reduction rate, especially for aerobic reduction. The presence of 3000 mg L(-1) acetate enhanced anaerobic and aerobic Cr (VI)-reduction rates up to 9.47 mg g(-1)min(-1) and 4.42 mg g(-1)min(-1), respectively, which were 5 and 20 times faster than those without it. Strain LSSE-09 retained high activities over six batch cycles and NO(3)(-) and SO(4)(2-) had slightly negative effects on Cr (VI)-reduction rates. The results suggest that strain LSSE-09 has potential application for Cr (VI) detoxification in alkaline wastewater.

Desulfurization of Diesel Fuel by Extraction with Lewis-Acidic Ionic Liquid

Abstract Ionic liquids were found to be highly selective for the extractive removal of aromatic sulfur compounds from fuels at room temperature. The efficiency of ionic liquids for the removal of aromatic sulfur compounds is dependent on the properties and structure of the ionic liquids. In this work, the Lewis-acidic ionic liquid 1-butyl-3-methylimidazolium tetrahalogenoferrate(III) ([BMIM] [FeCl4]) was synthesized and demonstrated to be more effective for the removal of aromatic sulfur compounds from diesel over ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM] [BF4]) because of its Lewis-acidic property. The ionic liquids favorably extracted organic compounds with a higher density of aromatic π-electrons. [BMIM][FeCl4] ionic liquid can be regenerated through reextraction by hexane, and could be used in multiple steps for the removal of sulfur compounds from diesel.

Kinetic evaluation of products inhibition to succinic acid producers Escherichia coli NZN111, AFP111, BL21, and Actinobacillus succinogenes 130Z(T)

Succinic acid is one of the platform compounds and its production via natural feedstocks has drawn worldwide concerns. To evaluate the inhibitory effects of fermentation products on the growth of Actinobacillus succinogenes 130ZT and Escherichia coli NZN111, AFP111, BL21, fermentations with addition of individual products in medium were carried out. The cell growth was inhibited when the concentrations of formate, acetate, lactate, and succinate were at range of 8.8–17.6 g/L, 10–40 g/L, 9–18 g/L, and 10–80 g/L, respectively. For these two species of bacteria, E. coli was more resistant to acid products than A. succinogenes, while both endured succinate rather than by-products. As a result of end product inhibition, succinate production yield by A. succinogenes decreased from 1.11 to 0.49 g/g glucose. Logistic and Monod mathematical models were presented to simulate the inhibition kinetics. The Logistic model was found more suitable for describing the overall synergistic inhibitory effects.

Enhancement of Biodesulfurization in Two-Liquid Systems by Heterogeneous Expression of Vitreoscilla Hemoglobin

ABSTRACT The vgb gene, encoding Vitreoscilla hemoglobin (VHb), was introduced into a specific desulfurization bacterium, Rhodococcus erythropolis LSSE8-1. The VHb-specific spectrum was observed for the recombinant. Compared to the wild type, the strain bearing vgb showed a higher biomass yield and desulfurizing activity.

Bio-regeneration of π-complexation desulfurization adsorbents

The coupling of adsorption desulfurization and biodesulfurization is a new approach to produce clean fuels. Sulfur compounds are firstly adsorbed on adsorbents, and then the adsorbents are regenerated by microbial conversion. п-Complexation adsorbent, Cu(l)-Γ, was obtained by ion exchanging Γ-type zeolite with Cu2+ and then by auto-reduction in helium at 450°C for 3 h. Dibenzothiophene (DBT) was used as a model compound. The effects of cell concentration, volume of oil phase, the ratio of aqueous phase to adsorbent on DBT desorption by a bacterium were studied. The amounts of DBT desorbed and 2-HBP produced can be apparently increased with addition of n-octane. BDS activity can be improved by increasing cell concentration and the ratio of water-to-adsorbent. 89% of DBT desorbed from the adsorbents can be converted to 2-HBP within 6 h and almost 100% within 24 h, when the volume ratio of oil-to-water was 1/5 mL/mL, the cell concentration was 60 g·L-1, and the ratio of adsorbent-to-oil was 0.03 g- mL-1. The amount of 2-HBP produced was strongly dependent on the volume ratio of oil-to-water, cell concentration and amount of adsorbent. Adsorption capacity of the regenerated adsorbent is 95% that of the fresh one after being desorbed with Pseudomonas delafieldii R-8, washed with n-octane, dried at 100°C for 24 h and auto-reduced in He.

Bio‐Regeneration of Desulfurization Adsorbents by Selected P. delafieldii R‐8 Strains

Abstract Adsorption properties of different adsorbents such as reduced NiY, AgY, alumina, 13X, and activated carbon were studied with dibenzothiophene (DBT) and naphthalene as model compounds. The desorption of DBT was carried on thermo gravimetric–differential thermal analysis (TG‐DTA). The interaction of DBT with different adsorbents follows the sequence: activated carbon > reduced NiY > AgY > activated alumina > 13X. The bio‐regeneration of these adsorbents was studied with P. delafieldii R‐8 as desulfurization strains. Adding P. delafieldii R‐8 cells can improve DBT desorption from adsorbent AgY. The desorption of DBT from adsorbents by bio‐regeneration of adsorbents follows the sequence: 13X > alumina > AgY > reduced NiY>activated carbon. The presence of naphthalene can decrease the desorption of sulfur compounds. The adsorption capacity of AgY decreases for the first time recycling and then changes little. The decrease of the adsorption capacity is due to the loss of Ag+ ions.