[Show abstract][Hide abstract] ABSTRACT: Bacillus coagulans IPE22 was used to produce lactic acid (LA) from mixed sugar and wheat straw hydrolysates, respectively. All fermentations were conducted under non-sterilized conditions and sodium hydroxide was used as neutralizing agent to avoid the production of insoluble CaSO4. In order to eliminate the sequential utilization of mixed sugar and feedback inhibition during batch fermentation, membrane integrated repeated batch fermentation (MIRB) was used to improve LA productivity. With MIRB, a high cell density was obtained and the simultaneous fermentation of glucose, xylose and arabinose was successfully realized. The separation of LA from broth by membrane in batch fermentation also decreased feedback inhibition. MIRB was carried out using wheat straw hydrolysates (29.72g/L glucose, 24.69g/L xylose and 5.14g/L arabinose) as carbon source, LA productivity was increased significantly from 1.01g/L/h (batch 1) to 2.35g/L/h (batch 6) by the repeated batch fermentation.
[Show abstract][Hide abstract] ABSTRACT: A thermophilic lactic acid (LA) producer was isolated and identified as Bacillus coagulans strain IPE22. The strain showed remarkable capability to ferment pentose, hexose and cellobiose, and was also resistant to inhibitors from lignocellulosic hydrolysates. Based on the strain's promising features, an efficient process was developed to produce LA from wheat straw. The process consisted of biomass pretreatment by dilute sulfuric acid and subsequent SSCF (simultaneous saccharification and co-fermentation), while the operations of solid-liquid separation and detoxification were avoided. Using this process, 46.12g LA could be produced from 100g dry wheat straw with a supplement of 10g/L corn steep liquid powder at the cellulase loading of 20FPU (filter paper activity units)/g cellulose. The process by B. coagulans IPE22 provides an economical route to produce LA from lignocellulose.
[Show abstract][Hide abstract] ABSTRACT: Production of acetone–butanol–ethanol (ABE) from cassava was investigated with a fermentation–pervaporation (PV) coupled process. ABE products were in situ removed from fermentation broth to alleviate the toxicity of solvent to the Clostridium acetobutylicum DP217. Compared to the batch fermentation without PV, glucose consumption rate and solvent productivity increased by 15% and 21%, respectively, in batch fermentation–PV coupled process, while in continuous fermentation–PV coupled process running for 304 h, the substrate consumption rate, solvent productivity and yield increased by 58%, 81% and 15%, reaching 2.02 g/L h, 0.76 g/L h and 0.38 g/g, respectively. Silicalite-1 filled polydimethylsiloxane (PDMS)/polyacrylonitrile (PAN) membrane modules ensured media recycle without significant fouling, steadily generating a highly concentrated ABE solution containing 201.8 g/L ABE with 122.4 g/L butanol. After phase separation, a final product containing 574.3 g/L ABE with 501.1 g/L butanol was obtained. Therefore, the fermentation–PV coupled process has the potential to decrease the cost in ABE production.
[Show abstract][Hide abstract] ABSTRACT: The pervaporation (PV) performance of a thin-film silicalite-1 filled PDMS/PAN composite membrane was investigated in the continuous acetone–butanol–ethanol (ABE) production by a fermentation–PV coupled process. Results showed that continuous removal of ABE from the broth at three different dilution rates greatly increased both the solvent productivity and the glucose utilization rate, in comparison to the control batch fermentation. The high solvent productivity reduced the acid accumulation in the broths because most acids were reassimilated by cells for ABE production. Therefore, a higher total solvent yield of 0.37 g/g was obtained in the fermentation–PV coupled process, with a highly concentrated condensate containing 89.11–160.00 g/L ABE. During 268 h of the fermentation–PV coupled process, the PV membrane showed a high ABE separation factor of more than 30 and a total flux of 486–710 g/m2h. Membrane fouling was negligible for the three different dilution rates. The solution-diffusion model, especially the mass transfer equation, was proved to be applicable to this coupled process.
[Show abstract][Hide abstract] ABSTRACT: Simultaneous extraction of oil and soy isoflavones from soy sauce residue (SSR) was investigated by means of the two-phase solvent extraction intensified by ultrasonication. A single factor test was first carried out to study the effects of ultrasonic time, ethanol concentration, ratio of ethanol/water phase to raw material, ratio of hexane phase to raw material, and ultrasonic power on the extraction rates of oil and isoflavones, then response surface methodology was applied to further optimize and simulate four key factors. The results showed that the extraction rates of oil and isoflavones of 92.07% and 92.53%, respectively, could be obtained when ethanol concentration was 74.88%, ratio of ethanol/water phase to raw material 15:1, ratio of hexane phase to raw material 8.64:1, extraction time 20 min, and ultrasonic power 160 W. The predictive rates were well matched with the experimental ones. The quality analysis of oil and soy isoflavones from SSR showed that the extracted oil with high acid value could be a potential raw material for biodiesel production instead of cooking. The extracted soy isoflavones existed mainly in aglycones form, which might afford higher bioactivity than that from the other soybean products.
Separation and Purification Technology 01/2014; 128:72–79. · 2.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bacillus coagulans IPE22 was used to produce lactic acid (LA) from mixed sugar and wheat straw hydrolysates, respectively. All fermentations were conducted under non-sterilized conditions and sodium hydroxide was used as neutralizing agent to avoid the production of insoluble CaSO4. In order to eliminate the sequential utilization of mixed sugar and feedback inhibition during batch fermentation, membrane integrated repeated batch fermentation (MIRB) was used to improve LA productivity. With MIRB, a high cell density was obtained and the simultaneous fermentation of glucose, xylose and arabinose was successfully realized. The separation of LA from broth by membrane in batch fermentation also decreased feedback inhibition. MIRB was carried out using wheat straw hydrolysates (29.72 g/L glucose, 24.69 g/L xylose and 5.14 g/L arabinose) as carbon source, LA productivity was increased significantly from 1.01 g/L/h (batch 1) to 2.35 g/L/h (batch 6) by the repeated batch fermentation.
[Show abstract][Hide abstract] ABSTRACT: Soy sauce is a traditional Chinese food condiment, normally containing a high concentration of sodium chloride (NaCl, 18–20%, w/v). To meet people's demand for healthy foods, part of NaCl needs to be removed from the raw soy sauce. In this study, nanofiltration was employed for the removal of salt and the recovery of nutritional components such as amino acid and fragrance from raw soy sauce, using four commercial NF membranes (NF270, NF-, NF90, Desal-5 DL). NF270 was found to be most suitable for the purpose. It was used to further study the effect of operation modes on desalination performance. The combination mode that concentration of the diluted soy sauce to its original volume, followed by diafiltration, was found to be most suitable one in terms of amino nitrogen (AN) and NaCl rejection, water consumption and operating pressure. Moreover, it was found that the rejection of AN was constant under the experimental conditions examined while NaCl rejection showed a linear relation with the concentration ratio of AN to NaCl. Based on mass balance and rejection equations, mathematical models were developed for predicting the concentration of solutes in retentate during desalination process, the simulation results agreed well with the experimental data.
Separation and Purification Technology 04/2013; · 2.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The desalination of model solutions containing iminodiacetic acid (IDA) and NaCl was examined using three commercial nanofiltration (NF) membranes (NF270, Desal-5 DL, Nanomax50). Experimental results showed that with all the three membranes, the rejection of IDA increased with the increase of pH from 8 to 11, and negative rejection of Cl− was found in filtration in a certain range of pH. NF270 was chosen to further investigate the effect of permeate flux, temperature and solutes concentration on the separation of IDA and NaCl. The results showed that IDA rejection decreased with the increase of temperature and salt concentration, and the high concentration of IDA could induce a lower rejection of NaCl. Furthermore, the desalination and recovery were examined with model solution in different operation modes and a laboratory scale test with an industrial fluid was also performed. Under suitable conditions, with NF270, the recovery of IDA could be more than 95% while the NaCl removal was greater than 58%.
Journal of Membrane Science 04/2013; · 4.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Application of combined ultrafiltration (UF) and nanofiltration (NF) was examined to recycle cellulase and concentrate glucose present in lignocellulosic hydrolyzate. With PES10 membrane operated at 25.6 l/m(2) h, 73.9% of cellulase protein present in the hydrolyzate suspension could be recovered while allowing free transmission of glucose. The permeate obtained from UF was then concentrated by NF. With NF270 membrane operated at 13.3 l/m(2) h, the glucose concentration in the ultrafiltered hydrolyzate increased from 30.2 to 110.2 g/l. Recycling cellulase by UF could reduce the hydrolysis cost of lignocellulosic feedstock, while concentrating glucose by NF could improve the fermentation efficiency of lignocellulosic hydrolyzate and lower the separation and purification cost of fermentative product. Therefore, the use of UF and NF for treating lignocellulosic hydrolyzate could be a promising approach in fermentative production of bioproducts and biofuels using lignocellulosic feedstock as substrate.
[Show abstract][Hide abstract] ABSTRACT: Furfural, found in the lignocellulosic prehydrolyzates at high concentration, is a strong inhibitor of growth and ethanol fermentation of Saccharomyces cerevisiae. Removal of furfural and concentration of monosaccharides were investigated by using two commercial nanofiltraton (NF) membranes with synthetic glucose-xylose-furfural solution as model. The effects of main operating parameters such as feed pH, permeation flux, temperature and feed concentration on the rejections of the three solutes, were studied. Results showed that rejections of the three solutes decreased with increasing feed pH and temperature, and increased with increasing permeation flux for both membranes. The concentrations of the three solutes had interaction effect on the rejection of furfural by NF90 membrane and rejections of the three solutes by NF270 membrane. Furthermore, the effects of two filtration modes, concentration and diafiltration, on the separation of furfural from monosaccharides were also investigated. With the two commercial NF membranes, concentration and purification of monosaccharides in the model solution can be accomplished.
[Show abstract][Hide abstract] ABSTRACT: The objective of this research was to investigate cellulase adsorption and recycling during enzymatic hydrolysis of two differently pretreated wheat straws (WS). Dilute acid treated WS showed lower hydrolysis yield of polysaccharides fraction and adsorbed more cellulase with hydrolyzed residue than dilute alkali treated sample. Four methods capable of recovering and recycling the enzyme bound to the residual substrate and the enzyme free in solution were used for three consecutive rounds of hydrolysis to compare their recycling efficiencies. Compared to the absorption recycling method, ultrafiltration recycling method possessed the capacity to retain β-glucosidase, thereby avoiding the supplementation of fresh β-glucosidase in subsequent rounds of hydrolysis. It was found that whatever recycling method was used, better recycling results were obtained for dilute alkali treated substrate than for dilute acid treated substrate. These results suggested that the great difference in the lignin content between acid treated WS and alkali treated WS would significantly affect enzymatic hydrolysis, cellulase adsorption and cellulase recycling efficiencies.
[Show abstract][Hide abstract] ABSTRACT: Antifouling ultrafiltration membranes were prepared by polyacrylonitrile-block-polyethylene glycol (PAN-b-PEG) copolymers through immersion precipitation phase inversion method. The effect of copolymer composition and PEG chain length on the structure and property of the block copolymer membranes were investigated. Compared with PAN membranes, PAN-b-PEG copolymer membranes possessed excellent hydrophilic surface due to the enrichment of PEG segments, which was confirmed by X-ray photoelectronic spectroscopy (XPS) and contact angle measurements. SEM images showed these PAN-b-PEG copolymer membranes had a typical asymmetric structure similar with PAN membranes, but the thinner skin layer was helpful for the membrane resistance reduction. The PAN-b-PEG copolymer membranes exhibited better antifouling ability for BSA than PAN membranes. The BSA absorption amount on the copolymer membrane could reduce 45% than that on the PAN membrane, and its irreversible fouling extent could lower 7 times. The hydrophilicity and antifouling ability of the copolymer membranes increased with increasing PEG content in the copolymer. While the chain length of PEG had little effect on the hydrophilicity and antifouling ability of the copolymer membrane.
[Show abstract][Hide abstract] ABSTRACT: To study the effects of different factors on the separation of acetone, butanol, and ethanol (ABE) from ABE–water solutions by pervaporation with silicalite-1/polydimethylsiloxane (PDMS) hybrid membranes, the adsorption of ABE in the silicalite-1 in acetone–butanol–water solution and ethanol–butanol–water solution was firstly investigated and then the separation of ABE from binary aqueous solutions at different feed concentrations and temperatures was examined. Experimental results showed that butanol could be preferentially adsorbed on silicalite-1 and the permeability of acetone through the membrane was the highest, followed by butanol and ethanol, which was not consistent with the predictions based on the experimental results of adsorption and membrane swelling measurement. This could be explained by Hansen solubility parameters for the component and polymer interactions (δm,c) and for the organic solvent and water interactions (δw,i). In the separation of ABE–water solution by the silicalite-1/PDMS hybrid pervaporation membranes, acetone and ethanol could promote ABE transport through membrane and block water permeation, and the membrane performance could be significantly affected by vacuum pressure in the permeate side.
Separation and Purification Technology - SEP PURIF TECHNOL. 01/2011; 79(3):375-384.
[Show abstract][Hide abstract] ABSTRACT: Pretreating wheat straw (WS) with combined use of varied sulfuric acid concentration (0-3%, w/v) and Tween 20 concentration (0-1%) was investigated in an attempt to enhance the hydrolysis and fermentability of pretreated WS. Enzymatic hydrolysis yield of glucan and xylan and ethanol production by simultaneous saccharification and fermentation (SSF) of water-insoluble solids (WIS) were significantly affected by the amount of Tween 20 added during acid pretreatment. Any further addition of Tween 20 in either hydrolysis stage or fermentation stage only led to small increase in glucan conversion and ethanol production. Determination of adsorption of cellulases during hydrolysis showed that Tween 20-assisted acid treated straw solution contained more free cellulases than individual acid treated straw solution, indicating that modification of lignin surface by Tween 20 added during pretreatment likely occurred. In addition, the effects of pretreatment conditions on overall recovery of glucose and xylose after pretreatment and enzymatic hydrolysis were also investigated.
[Show abstract][Hide abstract] ABSTRACT: The effects of five alternative nitrogen sources, namely, malt sprout (MS), corn steep liquor (CSL), NH4Cl, NH4NO3 and diamine citrate (DC) were investigated on the l-(+)-lactic acid (LA) production by thermophile Lactobacillus plantarum As.1.3. Through the statistical analysis of the results by three steps of response surface methodology (RSM) design, MS and CSL were found to have significant effects on the LA production and their optimal concentrations in the medium should be 16.0 g/L and 12.0 g/L, respectively. The verification of the optimized medium showed that the maximum specific growth rate (μm) was 1.09 h−1, the cell yield coefficient (YX/S) and the l-(+)-lactic acid yield coefficient (YP/S) were 0.233 (OD620/g) and 0.98 (g/g), and the maximum volumetric productivity and the average volumetric productivity were 13.0 g/L h and 3.20 g/L h, respectively. The results indicate that the LA production can also be enhanced with the inexpensive nitrogen source alternatives.
[Show abstract][Hide abstract] ABSTRACT: In preparation of inorganic particles filled polymer membranes, coupling agents can help to improve the compatibility between inorganic filler and polymer matrix. In this paper, surface modification of silicalite-1 was performed by a coupling agent, vinyltrimethoxysilane (VTMS), and hybrid pervaporation membranes were prepared by incorporating the unmodified or VTMS-modified silicalite-1 into polydimethylsiloxane (PDMS). The VTMS-modified silicalite-1 particles and hybrid membranes were characterized by FT-IR, 29Si CP MAS NMR, DSC, TGA, XRD and SEM. The results showed that the coupling agent VTMS was readily grafted on the surface of silicalite-1 by hydrolysis reaction and condensation reaction, and the chemical linking between the –CHCH2 group on the surface-modified silicalite-1 and –Si–H on the PDMS substantially eliminated the nonselective voids inside the membrane. When used to separate acetone, butanol, ethanol (ABE) from aqueous solution, a higher selectivity was obtained with the VTMS-modified silicalite-1/PDMS hybrid membrane. Moreover, the surface modification of silicalite-1 improved its dispersion in PDMS and increased the maximal loading of silicalite-1 in membrane preparation, and thus further enhanced the separation factor of the membrane.
Separation and Purification Technology - SEP PURIF TECHNOL. 01/2010; 75(3):286-294.
[Show abstract][Hide abstract] ABSTRACT: An electro-ultrafiltration process was proposed and developed for concentrating protein solution rapidly by applying an electric field and employing a membrane with a higher nominal molecular weight cut-off (NMWCO) than the molecular weight of protein to be concentrated. In this process, the high NMWCO membrane was used to achieve a high permeate flux while the adoption of an electric field was used to obtain a high rejection of the target protein by manipulating the electrophoretic effect. Bovine serum albumen (BSA) was used as a model protein, and 50 and 100 kDa NMWCO polysulphone (PS) membranes were used for BSA concentration. The effects of membrane NMWCO, electric field strength, feed concentration on permeate flux and protein rejection were examined. The experimental results showed that the concentration time required for a target protein concentration could be significantly shortened when an electric field was applied and a membrane with higher NMWCO was used. When a 3000 V m−1 electric field was applied and the 100 kDa NMWCO polysulphone (PS) membrane was used, the concentration time for concentrating 0.5 g L−1 BSA solution to around 1.0 g L−1 decreased by 80% as compared with the process with a 50 kDa membrane without electric field, suggesting that this electro-ultrafiltration concentration process is a viable alternative to conventional ultrafiltration process and a promising method for concentrating dilute protein solutions.
Separation and Purification Technology 01/2010; 73(2):310-318. · 2.89 Impact Factor