Batch production of biosurfactant with foam fractionation

Methods of producing the biosurfactant surfactin from cultures of Bacillus subtilis (BBK006) have been investigated. A reactor with integrated foam fractionation was designed and used in batch mode, and the performance compared with that of the same culture in shaken flasks. In the batch reactor, significant foaming occurred between 12.5 h and 14.5 h of culture time. During this period, the foam was routed through the foam fractionation column to a mechanical foam breaker, and a biosurfactant‐enriched foamate was collected. Concentration of surfactin in the foamate product was around 50 times greater than that in the culture medium. Using the integrated reactor, 136 mg L^?1 of surfactin was produced, significantly more than was achieved in shaken flasks (92 mg L^?1). The foam fractionation method allowed a real‐time measurement of the rate of surfactin production during growth. This showed that the maximum rate of production occurred at the interphase between log and stationary modes of growth, in contrast to previous work showing that surfactin is exclusively a secondary metabolite. The high value of surfactin yield in relation to biomass (Y_P/x = 0.262) indicated that surfactin was produced very efficiently by Bacillus subtilis (BBK006) in this integrated bioreactor. Copyright © 2006 Society of Chemical Industry     

Continuous production of biosurfactant with foam fractionation

A glucose‐limited chemostat was used to determine the growth parameters of BBK006 for continuous production of the biosurfactant surfactin. The continuous cultivation exhibited low maintenance metabolism (m = 0.39 mmol_glucose g_bacteria^?1 h^?1) and high molar growth yield ( g_bacteria mol_glucose^?1). It was found that the surfactin production rate in continuous culture was not only a function of dilution rate but also varied with the initial concentration of glucose in the feed. A high steady state concentration of surfactin (18 mg L^?1) was maintained in the culture at a dilution rate of 0.2 h^?1 when glucose concentration in the feed was 0.25 g L^?1. This is the first demonstration of continuous surfactin production and recovery using glucose as a carbon source. The production of surfactin is known to be related to the age of the microorganisms and a simple mathematical model has been constructed to show how the age‐related production can be quantified. Copyright © 2006 Society of Chemical Industry     

Foaming properties of surfactin,a lipopeptide biosurfactant fromBacillus subtilis

Foaming properties of surfactin were investigated and compared to those of sodium dodecyl sulfate (SDS) and bovine serum albumin (BSA). Foams were formed by a bubbling technique. Evolution of the foam volume and the liquid in the foam was monitored with optical and conductimetric methods to characterize foam formation and stability. Excellent foaming properties of surfactin were shown by its higher ability to form and stabilize the foam at a concentration as low as 0.05 mg/mL, in comparison with SDS and BSA. Surfactin produced a foam with intermediate maximum density and stabilized the liquid in foam, as well as BSA.     

Removal of trace Cu from aqueous solution by foam fractionation

A system for removal of Cu²⁺ from aqueous solution by foam fractionation is proposed. The effects of pH, gas flow rate, surfactant concentration and froth/solution ratio on the removal rate and the enrichment ratio were studied to optimize the conditions. The results show that the removal rate increased with gas flow rate decreased, surfactant concentration increased and the froth/solution ratio increased, and was higher at pH4.0-5.0 than at other pH value. The optimum separation conditions were pH5.0, 200 mL/min of gas flow rate, 0.15 g/L of surfactant concentration and 1.1 of froth/solution ratio. Under the optimum conditions, the removal rate was 97.2% and the enrichment was 53.0.     

泡沫分离法脱除铜离子色素工艺

在水溶液中,相当一部分色素在一定条件下带正电荷或负电荷,因此文中以水溶液中的铜离子为色素研究体系,十二烷基硫酸钠(SDS)为起泡剂,探索泡沫分离法脱除水溶液中离子色素的工艺。单因素实验研究了铜离子色素脱除率和富集比随pH值、鼓泡气体流量、表面活性剂质量浓度及泡沫塔装液量的变化规律和机理,结果表明,十二烷基硫酸钠对泡沫分离法脱除铜离子色素具有良好的效果。在此基础上通过正交实验得到最佳操作工艺为:pH值5.0,气体流量80 mL/min,表面活性剂质量浓度0.15 g/L,装液量220 mL,此工艺下铜离子色素脱除率为99.4%,富集比为20.8。     

Removal of cadmium and lead from soil using aescin as a biosurfactant

Remediation of a soil contaminated with cadmium or lead was performed by a soil washing process using aescin as a biosurfactant. The removal of cadmium and lead from the soil was evaluated as a function of aescin concentration and pH in a batch process. A 30-mM aescin solution was most effective in the removal of cadmium and lead at pH 6.8. Cadmium and lead migrated from the soil to the aescin-containing aqueous phase, depending on the pH value. We found that 41% of cadmium (pH 7.8) and 25% of lead (pH 2.8) in the soil matrix migrated into a 30-mM aescin solution. Also, the complexation of aescin with cadmium and lead ions was confirmed by Fourier transform infrared spectroscopy and electrical conductivity measurements. As a result, the maximal complexation capacity of aescin with metal ions was approximately aescin/cadmium=2∶1 and aescin/lead=3∶1 on a molar basis. It was suggested that aescin may sequester cadmium and lead ions by the carboxylic and saccharide moieties. Then, the complex of aescin with cadmium or lead may migrate to the aqueous phase as the result of dispersion.     

间歇式泡沫分离法回收海水中硼的研究

采用间歇式泡沫分离法研究了海水中硼的回收工艺。主要考察了表面活性剂种类及用量、溶液pH、气体流量等因素对海水中硼的分离性能的影响。实验结果表明：十二烷基三甲基氯化铵（DTAC）、十四烷基三甲基氯化铵（TTAC）、十六烷基三甲基氯化铵（CTAC）以及十八烷基三甲基氯化铵（OTAC） 4种表面活性剂中CTAC对海水中硼的分离效果最好;随溶液pH的增加,硼的回收率和富集比均先增大后减小;随CTAC用量的增加,硼的回收率逐渐增大并趋于稳定,而富集比先增大后减小;随气体流量的增加,硼的回收率先增大后减小,而富集比则逐渐减小。在实验条件范围内,当CTAC质量浓度为0.2 g/L、溶液pH为9、气体流量为200 mL/min时,硼的回收率达到90%,富集比达到8。     

On the drift‐flux analysis of flotation and foam fractionation processes

Drift‐flux analyses are a common way of estimating the phase fractions and fluxes in vertical multiphase flows. However their use has had scant impact on the flotation and foam fractionation communities despite the publication of a number of such analyses over the past two decades. By recognizing that the physics that underpin the hydrodynamics of the froth are dissimilar to those that pertain to the bubbly liquid beneath, we present a drift‐flux analysis with two characteristic curves. A method for obtaining the characteristic curve for the froth from experimental data for the drainage of stationary foams is presented.     

Synthesis of brushite particles in reverse microemulsions of the biosurfactant surfactin

In this study the "green chemistry" use of the biosurfactant surfactin for the synthesis of calcium phosphate using the reverse microemulsion technique was demonstrated. Calcium phosphates are bioactive materials that are a major constituent of human teeth and bone tissue. A reverse microemulsion technique with surfactin was used to produce nanocrystalline brushite particles. Structural diversity (analyzed by SEM and TEM) resulted from different water to surfactin ratios (W/S; 250, 500, 1000 and 40,000). The particle sizes were found to be in the 16-200 nm range. Morphological variety was observed in the as-synthesized microemulsions, which consisted of nanospheres (~16 nm in diameter) and needle-like (8-14 nm in diameter and 80-100 nm in length) noncalcinated particles. However, the calcinated products included nanospheres (50-200 nm in diameter), oval (~300 nm in diameter) and nanorod (200-400 nm in length) particles. FTIR and XRD analysis confirmed the formation of brushite nanoparticles in the as-synthesized products, while calcium pyrophosphate was produced after calcination. These results indicate that the reverse microemulsion technique using surfactin is a green process suitable for the synthesis of nanoparticles.     

Removal of inorganic mercury from mine waste water by ion exchange

The present study has been undertaken to investigate a process that might remove inorganic mercury from mine waste water streams by use an ion exchange resin system. A number of commercial resins have been evaluated as ion exchangers and the mercury content of the waste water, ranging from 70 to 90 ppm, is reduced to a permitted level of 34 ppb. Dowex XZS‐1, a strong cationic ion exchanger in a gel Form, has the most pronounced selectivity for mercury. The loaded resin was regenerated efficiently using HCl solutions, due to increased competition between Hg and hydronium ions and formation of an HgCl ₄ ²⁻ ionic complex. © 2000 Society of Chemical Industry     

大豆蛋白废水中乳清蛋白的泡沫分离实验

采用泡沫分离法回收大豆蛋白废水中蛋白,考察了pH值、气体的流速、进料浓度、液柱和泡沫层高度等因素对分离效果的影响.低进气速度、高泡沫层高度、适当的pH值以及低进料浓度有利于较好的分离.结果表明:当进料浓度为0.54 g/L、pH值为5、泡沫层与液池高度比4∶1,通气量为15.0 L/h 时,富集比可以达到3.25;当进料浓度为0.54 g/L、pH值为5、泡沫层与液池高度比3∶1,通气量为15.0 L/h,此时脱除率可以达到48.5%.     

负载氧化镧泡沫玻璃脱除水中氟离子

饮用水中过量的氟会对人体造成危害,因此发展成本低、高效率除氟材料对于高氟地区饮用水安全和含氟废水处理很有必要。以泡沫玻璃为载体,采用浸渍法制备了泡沫玻璃负载氧化镧的复合材料。对复合材料组成、表面形貌、镧的溶出率和除氟效果做了表征。结果表明：负载氧化镧7%（质量分数）的泡沫玻璃除氟效果最佳,用100 g的该材料就可以将600 mL废水中的氟离子质量浓度从32 mg/L降至1 mg/L以下,达到了饮用水标准。使用过的复合材料通过草酸溶液处理,于600 ℃下热解,可以使复合材料再生。     

Removal and recovery of mercury from chloride solutions by contact deposition on iron felt

This paper deals with the use of iron felt as a reducing agent for the removal of mercury from aqueous dilute solutions containing chloride ions. The kinetic behavior of the mercuric ion reduction was analyzed and its diffusion coefficient was determined with the use of a rotating disk electrode. Experimental results of the removal of mercury from aqueous sodium chloride solutions containing 100 ppm mercury by contact with iron felt are reported. The mercury concentration was decreased to values lower than 0·1 ppm. The recovery of metallic mercury by chemical attack of the residual iron felt was also analyzed.     

双硫腙接枝聚氨酯泡塑吸附材料的制备及其除汞性能的研究

研究了双硫腙(H2D2)接枝聚氨酯泡塑(PU Foam)吸附材料的制备,考察了螯合泡塑的合成及从含汞废水中除汞的最佳条件。结果表明,该吸附材料对Hg2+具有良好的螯合吸附作用,且除汞效果明显,对8 mg/L含Hg2+废水,在pH为6,固液比为1∶100,温度15℃条件下螯合反应4 h,汞去除率可高达99.99%以上,一次处理后溶液中Hg2+含量低于0.000 8 mg/L,达到了国家饮水标准。且由吸附等温线可知,该过程属于Langmuir单分子层吸附过程,饱和吸附量为2.17 mg/g,可对水中痕量Hg2+进行深度吸附处理。由此,获得了一种新型的、合成工艺简单、成本低廉的含汞废水处理材料。     

KBr和KI改性黏土脱除模拟烟气中的单质汞

黏土是一种非常廉价的天然矿物,为了考察溴和碘改性黏土（膨润土）脱除烟气中单质汞的特性,采用浸渍法分别制备了KBr和KI改性黏土（KBr-clay和KI-clay）。在固定床吸附实验台上进行了脱除Hg⁰的实验研究,考察不同的负载量、吸附温度以及烟气中SO₂和水蒸气等对KI-clay和KBr-clay脱除单质汞的影响。研究结果表明：改性后黏土的比表面积、孔隙结构未发生显著的改变,表面官能团也没有发生本质的变化。KI-clay和KBr-clay脱汞能力大大提高,在同等实验条件下,KI-clay脱汞性能优于KBr-clay。研究表明单质汞在改性黏土表面产生了化学吸附,烟气中低浓度SO₂的存在对汞脱除有一定的促进作用,在相同的实验条件下,SO₂ 对KBr-clay促进作用更加明显,但水蒸气在低温下对脱汞具有很强的抑制作用,提高吸附温度可以消弱水蒸气的负面影响。     

Heavy metal removal from water using the metallogelation properties of a new glycolipid biosurfactant

Water pollution by heavy metals is a problem in both western and developing countries. Heavy metal pollution can be associated with human activity, such as wastewaters from processing of ore mining, but also to simple contamination from metal-rich soils. Whichever the case, chemical and physical methods are generally employed to depollute water. Since most chemicals are themselves polluting agents, there is an increasing interest in finding biobased and biodegradable alternative chemicals, both efficient in removing metals and benign to the environment. Biosurfactants are green chemicals produced by fermentation of yeasts and bacteria and with a good environmental score. Among many applications, this class of compounds has been used to remove heavy metals from contaminated soils. Within this framework, we propose a new mechanism of depolluting water using a glucolipid biosurfactant, G-C18:1, composed of glucose (G) and a C18:1 fatty acid (oleic acid). This compound is able to form a metallogel by complexing cations in water, thus trapping heavy metals (Cu²⁺, Ni²⁺, Cr²⁺, and Co²⁺) in the gel phase. This mechanism allows to remove up to 95% for cobalt and 88 ± 10%, 80 ± 3%, and 59 ± 6% for Cu²⁺, Ni²⁺, and Cr²⁺, respectively. A dedicated structural study shows that this is possible because positively charged species induce gelation of G-C18:1 through a micelle-to-wormlike phase transition, most likely driven by a charge neutralization process. This work shows that wise control of the nanoscale properties of green chemicals can strongly benefit to develop a sustainable future.     

Process intensification of foam fractionation by successive contraction and expansion

Enrichment in foam fractionation is enhanced by reducing the liquid flux while maintaining the flux of bubble surfaces. We show that it is possible to do so in a continuous foam fractionation column by inserting a plate into the foam layer and forcing the foam through a narrower tube (foam riser) mounted at the centre of the plate. A 35% reduction in liquid flux was observed by using a single plate-foam riser assembly in a foam stabilised by 0.52 g/L sodium dodecyl sulphate solution, and the liquid rejected from the foam due to the presence of the foam riser had the same concentration as the feed solution. However, due to the nature of the adsorption isotherm of SDS, the enrichment enhancement measured in the experiments hererin was modest. The mechanism of the foam riser plate was explained by invoking recent theoretical studies on pneumatic foam. It was demonstrated that the reduction in liquid flux was affected by sudden expansion of the flow area causing a rejection of interstitial liquid to the top of the plate and extracted, whence it was recycled back to the feed. Preliminary experiments on the effect of liquid pool depth and foam height on interfacial adsorption were also carried out to demonstrate that the insertion of the plate does not affect the adsorption of the target substance to the bubble surface in the current system. It was found that equilibrium could be achieved within 0.2 m of liquid pool depth or foam height, however the equilibrium surface excess on a rising bubble in the liquid pool is roughly 51% of the equilibrium value on a quiescent interface, while that in the foam layer is roughly 73% of the equilibrium value on a quiescent interface.     

基于甘草配伍黄芩同时泡沫分离甘草酸和黄芩苷

为了同时分离甘草中有表面活性的甘草酸和黄芩中无表面活性的黄芩苷,开发了甘草配伍黄芩泡沫分离工艺。通过荧光光谱、紫外吸收光谱和红外吸收光谱分析表明,甘草酸与黄芩苷存在相互作用,并且甘草黄芩配伍强化了甘草酸和黄芩苷的提取。以甘草酸和黄芩苷的富集比和回收率为评价指标,当温度为40℃、气体体积流量为100 ml·min^-1、甘草酸初始浓度为0.2 g·L^-1、甘草黄芩质量比为3：1时,获得甘草酸的富集比和回收率分别为11.0和73.5%,黄芩苷的富集比和回收率分别为5.8和38.5%。通过甘草与黄芩配伍,利用泡沫分离获得黄芩中的黄芩苷。同时,与单独泡沫分离甘草中甘草酸相比,甘草酸的富集比提高了194.9%,回收率提高了23.3%。因此,甘草配伍黄芩能有效泡沫分离甘草酸和黄芩苷。     

Removal of cellulose from sunflower meal by fractionation

The dependence of sunflower meal fractionation on the following factors was investigated: quality of original meals, 37.5%, 40.0% and 42.5% crude protein; screen hole size, 1.5 mm, 2.0 mm, 2.5 mm and 3.0 mm; and single-phase and two-phase fractionation. The following conclusions were drawn. The increased protein levels in original meals (from 37.5% to 42.5% crude protein) had considerably greater effects on the quality than on the yield of the protein fractions. Increased screen hole size (from 1.5 mm to 2.5 mm) increased the yield of the protein fractions by 16.4–22.3%, but reduced the protein level in these fractions by 2.3–2.8%. Two-phase fractionation of the original meals with 40.0% and 42.5% crude protein increased the protein yield in the resulting protein fractions by 15.5–22.8%. The most efficient fractionation procedures rendered high yields of attractive protein fractions that contained 44.0–47.5% crude protein. The protein fractions were analyzed for physico-functional constants and amino acid composition. The most efficient and applicable fractionation procedures, those that may be successfully used in oil refineries, were selected.