Separation Of Lactic Acid Research Articles

Influences of exopolysaccharide producing cultures on the quality of plain set type yogurt

Different strains of yogurt starter cultures and different incubation temperatures were investigated in the production of plain, unflavored set type yogurt. Milk samples were inoculated with 2% CH-1 (non-filant type which does not produce any ropy like substances) and B-3 (filant type which produces ropy like substances), and then incubated at 35 and 45 °C until the pH reached 4.7. Total solids, fat content, pH, viscosity, consistency, whey separation, organoleptic evaluation and content of lactic acid, acetaldehyde, volatile fatty acids and tyrosine were measured as quality criteria on the yogurt samples at Days 1 and 14 of storage. Lactic acid content and pH values of samples were more significantly affected by starter culture strain than by incubation temperature ( P<0.01). Among these treatments, use of different culture strains affected tyrosine and acetaldehyde contents of yogurts. Yogurt samples made from milk inoculated with CH-1 culture and incubated at 35 °C had the highest acetaldehyde content. Consistency and viscosity of yogurts increased when made from milk inoculated with exopolysaccharide producing culture (B3) and incubated at 35 °C. Whey separation was decreased more with B-3 yogurt produced at 35 °C than with yogurt made with CH-1 at the same incubation temperature. During the 14-day storage, the rheological properties of all yogurts were scored higher, and the content of lactic acid, volatile fatty acids, and tyrosine increased while pH values and amount of acetaldehyde were decreased.

Electrodialysis as a useful technique for lactic acid separation from a model solution and a fermentation broth

A two-stage electrodialysis (ED) method was used for lactic acid recovery. In the first step sodium lactate was concentrated with desalting electrodialysis using ion exchange membranes Ralex (Mega, Czech Republic). The second step was the electroconversion of sodium lactate to lactic acid by electrodialysis with bipolar membranes (EDBM) Neosepta (Tokuyama Corp., Japan). The lactic acid was recovered from model solutions and from real fermentation broth as well. The trials with model solutions were focused on determination of the suitable conditions for electrodialysis experiments and on investigation of the time course under different conditions. The fermentation broth from lactic acid fermentation had to be pretreated before electrodialysis experiments. The pretreatment consisted of ultrafiltration, decolourisation and removing of multivalent metal ions. In the first ED step the final lactate concentration of 175 g/l was obtained and afterwards the final lactic acid concentration of 151 g/l was reached in the second ED step.

A hollow-fiber membrane extraction process for recovery and separation of lactic acid from aqueous solution.

An energy-efficient hollow-fiber membrane extraction process was successfully developed to separate and recover lactic acid produced in fermentation. Although many fermentation processes have been developed for lactic acid production, an economical method for lactic acid recovery from the fermentation broth is still needed. Continuous extraction of lactic acid from a simulated aqueous stream was achieved by using Alamine 336 in 2-octanol contained in a hollow-fiber membrane extractor. In this process, the extractant was simultaneously regenerated by stripping with NaOH in a second membrane extractor, and the final product is a concentrated lactate salt solution. The extraction rate increased linearly with an increase in the Alamine 336 content in the solvent (from 5 to 40%). Increasing the concentration of the undissociated lactic acid in the feed solution by either increasing the lactate concentration (from 5 to 40 g/L) or decreasing the solution pH (from 5.0 to 4.0) also increased the extraction rate. Based on these observations, a reactive extraction model with a first-order reaction mechanism for both lactic acid and amine concentrations was proposed. The extraction rate also increased with an increase in the feed flow rate, but not the flow rates of solvent and the stripping solution, suggesting that the process was not limited by diffusion in the liquid films or membrane pores. A mathematical model considering both diffusion and chemical reaction in the extractor and back extractor was developed to simulate the process. The model fits the experimental data well and can be used in scale up design of the process.

Production of lactic acid from paper sludge by simultaneous saccharification and fermentation.

Production of lactic acid from paper sludge has been performed by simultaneous saccharification and fermentation (SSF). The SSF process design was based on experimental data obtained from cellulose hydrolysis and fermentation. The SSF process was employed to avoid an excessively dense solution when the sludge content of the feed was higher than 15%; this is one of several benefits of SSF. The enzyme system used for hydrolysis of paper sludge for production of glucose was optimized. CMCase and beta-glucosidase with activities of 2.5 and 10 U mL(-1), respectively, were found to be optimum for hydrolyzing 5% sludge. In batch SSF 16 g L(-1) lactic acid was produced from 5% paper sludge with an yield of 80%. Paper sludge which served as a feed seemed to have a buffering effect during SSF, probably because of the inorganic ash component in the sludge. The final product concentration by SSF was observed to be limited by the cellulose content of the system, which can probably be resolved by intermittent feeding of the paper sludge. SSF of paper sludge fed in batch mode, with intermittent feeding, produced lactic acid at 162 g L(-1), with a yield of 74% and a productivity of 1.4 g L(-1) h(-1). The lactic acid production performance of the modified bioreactor improved after removal of indigestible solid materials from the upper compartment, which enabled the feed of paper sludge to be increased. A mathematical model is described which predicts glucose and subsequent lactic acid production on the basis of the rate expressions of each step of the SSF process. Saccharification kinetics were determined by experiments on enzymatic cellulose hydrolysis, by use of a Michaelis-Menten equation; growth kinetics of L. rhamnosus were determined by use of a Monod expression which incorporated lactic acid inhibition. The kinetic model is expected to predict the performance of the SSF process. For further use of the lactic acid, i.e. polylactic acid, it must be recovered and purified. Results from application of the simulated moving-bed (SMB) process for separation of lactic acid and acetic acid are given, as are several methods of lactic acid purification.

Recovery of l-(+)-lactic acid by anion exchange resin Amberlite IRA-400

Amberlite IRA-400 anion exchange resin was applied for the recovery of l-(+)-lactic acid from fermentation broth. Adsorption isotherm and breakthrough curves for the separation of l-(+)-lactic acid were obtained at pH 5.0 and 2.0, respectively. Different types of adsorption isotherms were found at pH above and below the p K a (3.86) of lactic acid. The isotherm was found to be a Langmuir type at pH 5.0, whereas the isotherm was type II (multilayer adsorption) at pH 2.0. At pH 5.0, the maximum adsorption capacity of the resin, q m and dissociation constant, K d were 222.46 mg/g wet resin and 60.7 mg/ml, respectively. Breakthrough curve for the separation of lactic acid from fermentation broth was also obtained. The maximum adsorption capacity (197.09 mg/g wet resin) at pH 5.0 was much higher than that at pH 2.0 (106 mg/g wet resin). Proper elution and washing conditions were sought by using H 2SO 4, methanol, ammonia or their mixtures as eluant. When column separation was performed at pH 5.0 by using 50% (v/v) methanol as washing solvent and 1.0 M H 2SO 4 as eluant, the total yield was 86.21%. However, the total yield was 92.11% when the column separation was performed at pH 2.0 and water was used as eluant.

Resin Selection and Single-Step Production and Recovery of Lactic Acid from Pretreated Wood

Four ion-exchange resins (Amberlite IRA 900, IRA 400, IRA 96, and IRA 67) were employed for lactic acid recovery from simultaneous saccharification and fermentation (SSF) media. The best resins (Amberlite IRA 900 and IRA 400) were assayed for capacity, regenerant consumption, percentage of lactic acid recovery, and product concentration. Almost quantitative lactic acid recoveries at constant capacities were achieved in four sequential loading/regeneration cycles. A strong-base resin (Amberlite IRA 400) was selected for intermittent lactic acid separation in a typical SSF process, in which pretreated wood was saccharified by cellulases in the presence of Lactobacillus delbrueckii. The dynamics of lactic acid generation and lactic acid recovery were established.

Separation characteristics of lactic acid in reactive extraction and stripping

Lactic acid has recently been drawing much interest as a raw material for biodegradable polymer. Various extractants for lactic acid separation were tested and TOA (trioctylamine) was found the most effective one. Lactic acid was separated by reactive extraction with TOA dissolved in various diluents. The effect of temperature on the extraction efficiency was smaller than that of composition for the system studied in this work.

Direct chiral resolution of lactic acid in food products by capillary electrophoresis

Chiral resolution of native dl-lactic acid was performed by capillary electrophoresis using 2-hydroxypropyl-β-cyclodextrin as a chiral selector. Various factors affecting chiral resolution, migration time, and peak area of lactic acid were studied. The running conditions for optimum separation of lactic acid were found to be 90 m M phosphate buffer (pH 6.0) containing 240 m M 2-hydroxypropyl-β-cyclodextrin with an effective voltage of −30 kV at 16°C, using direct detection at 200 nm. In order to enhance the sensitivity, sample injection was done under a pressure of 50 mbar for 200 s. On-line sample concentration was accomplished by sample stacking. With this system, d- and l-lactic acids in food products were analyzed successfully.

Separation of lactic acid from fermented broth by reactive extraction.

The separation of lactic acid from complex fermentation broth was examined. Liquid-liquid extraction using reversible chemical complexation for reactive extraction was chosen to be the separation method. Over 50% yield of lactic acid was obtained from fermented broth in a single extraction step, when using the tertiary amine as the extractant, 1-dekanol as the diluent and trimethylamine (TMA) as the stripping solution. The effect of complex media on the extraction behaviour has hardly been examined previously.

Comparative study of lactic acid and polylactides using static headspace, gas chromatography and high-performance liquid chromatography

This work investigates the use of analytical methodology to determine lactic acids and/or polylactides. This paper reports three methods that have been successfully developed. Firstly, static headspace gas chromatography (GC) was investigated. The results show precision values of 4–5% RSD and linearity correlation coefficients of between 0.990 and 0.999 in the concentration range 300–700 μg/ml lactic acid. The method is specific for lactic acid. Secondly, an on-column GC method is presented which minimises sample preparation and separation of lactic acid from the polylactides. Finally, an ion-exclusion high-performance liquid chromatography (HPLC) method was developed. The instrumental precision was 0.1%, and linearity correlation coefficients >0.9999 were obtained in the concentration range between 50 and 200 μg/ml lactic acid. A basic hydrolysis is used to convert the polylactides to lactic acid. Collectively, these methods form a successful approach for the determination of lactic acid in consumer healthcare products.

Separation of lactic acid using polymeric membrane containing a mobile carrier

A cellulose triacetate (CTA) membrane containing trioctylmethyl ammonium chloride (TOMAC) as a carrier and o-nitrophenyloctyl ether (NPOE) as a plasticizer was developed for the in situ separation of fermented lactic acid. The separation characteristics of the CTA-TOMAC-NPOE membrane were investigated. The permeation rate of lactate through the CTA-TOMAC-NPOE membrane was comparable to that through a supported liquid membrane. TOMAC played the role of a mobile carrier in lactate transport. It was found that the CTA-NPOE membrane containing TOMAC has the advantages of allowing a high flux of lactate and having a low solubility of TOMAC in aqueous solution.

MATHEMATICAL MODEL OF L-LACTIC ACID FERMENTATION IN A RDC COUPLED WITH PRODUCT SEPARATION BY ION EXCHANGE

A Rotating Disk Contactor (RDC) was designed to perform the L-lactic acid fermentation with a filamentous fungus, Rhizopus oryzae, which was immobilized on the surface of rotating disks. The bioreactor was operated in repeated batch or continuous modes. The growth rate of the fungi was about 1 mm/day perpendicular to the disks' surface. A weak-base anionic resin, D354, was selected which was high in selectivity for lactic acid separation. Even at low concentration, the ion exchange capability was about 0.5 g Lac/g dry resin. A coupled process of L-lactic acid fermentation and ion-exchange separation was evaluated experimentally. The results indicated that the pH value of the fermentation broth could be maintained at pH 3.5 without any addition of alkali. The conversion ratio of glucose to L-lactic acid was about 0.7 g/g and the fermentation rate was able to reach as high as 62.5g glucose per hour per square meter of the disk surface area. A mathematical model was proposed to describe the simultaneous process of L-lactic acid fermentation and separation by ion exchange, in which the thickness increase of mycelia as well as the substrate and product inhibitions were included. The model simulation was in good agreement with the experimental data.

Separation of Fermentation Products by Membrane Techniques. I. Separation of Lactic Acid/Lactates by Diffusion Dialysis

The results of the separation of lactic acid from sodium lactate by diffusion dialysis are presented in this paper. Neosepta AFN-7 and Selemion DSV membranes were used for the separation. The dialytic separation factor for lactic acid/sodium lactate was found to be ∼20 for Neosepta AFN-7 and ∼30 for Selemion DSV membranes. The fluxes inherent in the separation were up to ∼1 mol/m2·h for the acid and only up to ∼0.07 mol/m2·h for the salt. The effects that enable the separation, i.e., the differences in solubility and diffusivity of the acid and the salt, were estimated (single solute experiments). The partition coefficients for lactic acid were found close to or above unity whereas those for sodium lactate were much lower. On the contrary, the apparent diffusion coefficients of both solutes were comparable, being of the order of 10−11 m2/s. It results that the separation of the weak acid and salt is based on differences in solubilities rather than in diffusivities, i.e., the phenomenon is different from those which enable separation of strong acids and salts. The results prove the diffusion dialysis technique is effective for separating lactic acid from lactates.

Control of Swelling in Liquid Emulsion Membranes Employed for Lactic Acid Separation

Control of the swelling of two different liquid emulsion membrane systems for separation of lactic acid was examined. The major disadvantages of swelling are dilution of the separated product and emulsion breakage. Several additives including liquid paraffin, cyclohexanone and n-decanol were investigated with respect to both emulsion swelling and lactic acid separation rate. If swelling is a function of surfactant concentration, the swelling increases with the quantity of the hydrophilic part in the surfactant. Therefore, a surfactant with a low hydrophilic/lipophilic balance (HLB) value should be used to reduce the swelling. The use of Span 85 (HLB = 1·8) as co-surfactant achieved the objective in the case of a tri-n-octylamine/Span 80 system.

Separation and Purification of Lactic Acid; Thermal Catalytic Depolymerization of Poly-Lactic Acid into Lactide.

発酵乳酸の分離精製法として, ポリ乳酸の接触熱解重合法を利用してラクチドに転化して精製する方法は有効な方法である.この観点から, 本研究ではポリ乳酸をラクチドへ転化するための実用的な熱解重合触媒を探索した.鉄系触媒, 特に金属鉄, 酸化第一鉄, 乳酸第一鉄は, 従来使用されているオクチル酸錫や酸化アンチモンとほぼ同じ触媒活性を示し, ほぼ同じ熱解重合物組成を与えることを確認した.さらに酸化第一鉄触媒を発酵未精製乳酸より合成した粗乳酸ポリマーの熱解重合に適用した.純物質から合成したポリマーの熱解重合と比較して触媒活性, 熱解重合物組成もほぼ同じであることが確認され, かつこれらは毒性の心配がないことや安価であることから, 実用触媒として利用可能と判断された.また, 原料としての乳酸ポリマー性状を検討した結果, 熱解重合性と熱解重合物組成から判断して重量平均分子量Mw=5,000-10,000のポリマーが望ましいことが分かった.

5510526 Lactic acid production, separation and/or recovery process

5510526 Lactic acid production, separation and/or recovery process

Separation and purification of lactic acid: Fundamental studies on the reverse osmosis down-stream process

The physico-chemical properties and effects of lactic acid and lactates in the reverse osmosis process were investigated using a polyamide composite membrane. The membrane was found to swell at pH 2.2, yet has no detectable solute-membrane affinity. The decrease in flux and increase in the solute reduction factor of lactic acid (0.66 m 3.m −2.d −1; 5.8), ammonium lactate (0.30 m 3.m −2.d −2.d −1; 18.3) and sodium lactate (0.18 m 3.m −2.d −1; > 80) were found to be related to the concentration of ions dissociated into solution as affected by the pH of the feed. The effects of operating parameters such as pressure, feed concentration and stirring speed were also discussed. Optimum operating conditions were found to be 7 MPa and 900 rpm.

Enhanced Acid Extraction Using Amine-Loaded Compressed Carbon Dioxide

Compressed carbon dioxide, doped with secondary and tertiary amine entrainers, was used for the separation of acetic and lactic acid. The solubility of the amines in liquid and supercritical CO 2 was tested, and the partition of the acids between the aqueous and the amine-loaded gas phase was investigated. A model for the description of the phase equilibria based on the acid loading of the amine in the carbon dioxide phase was used. By performing semi-batch experiments, the rate determining step of the separation was found to be the interphase reaction. The applicability of this separation process was tested and found to be feasible in a continuously operated countercurrent lab-scale extraction plant

Comparison of the Production of Lactic Acid by Three Different Lactobacilli and its Recovery by Extraction and Electrodialysis

D(−)-Lactic acid was produced by Lactobacillus delbrueckii DSM 20072 (ATCC 9649) (LD), L (+)-lactic acid by Lactobacillus casei subsp. rhamnosus DSM 20021 (ATCC 7469) (LC) and by Lactobacillus salivarius subsp. salivarius DSM 20492 (ATCC 11742) (LS) on MRS medium and glucose substrate homofermentatively in batch cultures. LS exhibited the highest specific growth rate (μ = 1·41 h −1 ) and the highest specific productivity (π = 5·45 h −1 ). Acetate and citrate stimulated its growth. Substrate inhibition occurred at 30 g litre −1 glucose for LD, 26 g litre −1 glucose fo LC, and no inhibition was observed up to 100 g litre −1 glucose for LS. 60 g litre −1 lactate solution at pH 6 caused only slight product inhibition of LS. The product was extracted by four different amine carriers (Amberlite LA2, Hoe F2562, Hostarex A327 and Alamin 366) in the presence of modifiers (long-chain alcohols, alkylphosphates and acidic organic compounds) in kerosene and butylacetate, and a phosphinoxide (Cyanex 923). When using Hostarex A327 in oleylic alcohol or Cyanex 923 (phosphinoxide carrier) in kerosene or in oleylic alcohol, no modifier was necessary. The extent of lactic acid extraction was evaluated and the separation of lactic acid from citric and acetic acids was investigated. The re-extraction of the free acid under different conditions was not very successful. A maximum lactic acid yield of 72% was obtained. Except for kerosene and oleyl alcohol, the biocompatibility of the other chemicals was unsatisfactory. Their application for in situ extraction cannot be recommended. Recovery of the free lactic acid by electrodialysis and bipolar membrane is very promising. In situ recovery is possible.

Comparison of the Production of Lactic Acid by Three Different Lactobacilli and its Recovery by Extraction and Electrodialysis

D(−)-Lactic acid was produced by Lactobacillus delbrueckii DSM 20072 (ATCC 9649) (LD), L(+)-lactic acid by Lactobacillus casei subsp. rhamnosus DSM 20021 (ATCC 7469) (LC) and by Lactobacillus salivarius subsp. salivarius DSM 20492 (ATCC 11742) (LS) on MRS medium and glucose substrate homofermentatively in batch cultures. LS exhibited the highest specific growth rate (μ = 1·41 h −1) and the highest specific productivity (π = 5·45 h −1). Acetate and citrate stimulated its growth. Substrate inhibition occurred at 30 g litre −1 glucose for LD, 26 g litre −1 glucose fo LC, and no inhibition was observed up to 100 g litre −1 glucose for LS. 60 g litre −1 lactate solution at pH 6 caused only slight product inhibition of LS. The product was extracted by four different amine carriers (Amberlite LA2, Hoe F2562, Hostarex A327 and Alamin 366) in the presence of modifiers (long-chain alcohols, alkylphosphates and acidic organic compounds) in kerosene and butylacetate, and a phosphinoxide (Cyanex 923). When using Hostarex A327 in oleylic alcohol or Cyanex 923 (phosphinoxide carrier) in kerosene or in oleylic alcohol, no modifier was necessary. The extent of lactic acid extraction was evaluated and the separation of lactic acid from citric and acetic acids was investigated. The re-extraction of the free acid under different conditions was not very successful. A maximum lactic acid yield of 72% was obtained. Except for kerosene and oleyl alcohol, the biocompatibility of the other chemicals was unsatisfactory. Their application for in situ extraction cannot be recommended. Recovery of the free lactic acid by electrodialysis and bipolar membrane is very promising. In situ recovery is possible.