Nonconventional techniques for separation of biosynthetic amino acids.

Amino acids can be obtained by biosynthesis, by protein hydrolysis or by extraction from natural sources. The most efficient methods are the first two, but the separation of amino acids from fermentation broths or protein hydrolysates is rather difficult. Amino acids dissociate in aqueous solutions, forming characteristic ionic species depending on the solution pH-value. These properties make amino acids to be hydrophilic at any pH-value. This paper presents a review of the separation studies of some amino acids by nonconventional methods, namely individual or selective reactive extraction. Separation of some amino acids from their mixture obtained either by fermentation or protein hydrolysis by reactive extraction with different extractants indicated the possibility of the amino acids selective separation as a function of the pH-value of aqueous solution correlated with the acidic or basic character of each amino acid.

[Influences of internal diffusion on the lipids bio-degradation with immobilized Bacillus sp. cells in fixed bed of basket type]. / Implicatiile difuziei interne în biodegradarea lipidelor cu celulie imobilizate de Bacillus sp. dispuse in strat fix tip "basket".

AIM: This paper develops the previous studies on the transfer processes and biochemical reaction kinetics involved in the lipids biodegradation. MATERIAL AND METHODS: The experiments were carried out in 10 1(8 1 working volume) laboratory bioreactor with computer-controlled and recorded Parameters. The basket was placed centered around the stirrer and was filed with Bacillus sp. cells immobilized in alginate. The optimum impellers combination was found to be of two Rushton turbines, the superior one placed outside the basket and the other inside the basket at its inferior extremity. RESULTS: In the investigated case, the influences of the substrate internal diffusion on physical and biochemical processes have been quantified by means of the Biot number, Thiele modulus and reduction factor lambda. Compared to the system with free bacterial cells, biochemical processes rate is reduced inside the biocatalyst particle for about 150 - 200 times, this effect being more important than in the case of the bioreactor with mobile bed of immobilized yeast cells. CONCLUSIONS: The utilisation of immobilized biocatalysts offers many advantages, but allows the unfolding of the internal diffusion of substrate or product, with negative effect on the overall biochemical process evolution.

[Succinic acid production using mobile bed of immobilized Actinobacillus succinogenes in alginate]. / Obtinerea acidului succinic prin fermentatie cu strat mobil de Actinobacillus succininogenes.

UNLABELLED: This work investigates the production of succinic acid by immobilized A. succinogenes cells, using a bioreactor with stirred/mobile bed of biocatalysts. MATERIAL AND METHOD: The experiments have been carried out for different sizes of biocatalysts particle, under substrate and product inhibitory effects. RESULTS: The results indicated that the inhibitory effects could be diminished by cells immobilization, the substrate consumption rate increasing with the increase of biocatalyst particle size. Moreover, the biocatalysts can be used for many fermentation cycles.

[Improving the efficacy of synergetically facilitated pertraction of p-aminobenzoic acid by increasing the reextraction rate]. / Marirea eficientei pertractiei facilitate sinergetice a acidului p-aminobenzoic prin cresterea vitezei de reextractie din membrana lichida.

The studies on facilitated pertraction of PABA with Amberlite LA-2 and 1-octanol as phase modifier indicated the increase of the process efficiency and, implicitly, of the transport capacity of the liquid membrane by adding KOH in the stripping phase. Thus, the use of KOH led to the diminution of the kinetic resistance of the reextraction process, with positive effects on the acid final mass flow and permeability factor. Compared to the similar pertraction systems containing NaOH in the stripping phase and in direct correlation with the pertraction parameters (pH-gradient between the feed and stripping phases, carrier and alchohol concentrations inside the liquid membrane), the final mass flow can be accelerated for about 1.9 times, and the permeability through liquid membrane can be enhanced for about 1.5 times in presence of KOH.

[Selective separation of vitamin C and 2-ketogluconic acid by facilitated pertraction]. / Separarea selectiva a vitaminei C din amestec cu acidul 2-cetogluconic prin pertractie facilitata.

The removal of vitamin C from a mixture with 2-ketogluconic acid by using a bulk liquid membrane (BLM) has been investigated. The studies on facilitated pertraction of vitamin C with Amberlite LA-2 indicated the major parameters that affect the separation efficiency: pH gradient between the two aqueous phases, carrier concentration in the liquid membrane and phase mixing intensity. The overall results obtained in this work showed that liquid membrane system can effectively be used to selectively separate vitamin C from its mixture with the fermentation by-product, 2-ketogluconic acid.

[Analysis of oxygen transfer in bioreactors for fungus broths. 2. Suspensions of P. chrysogenum mycelial associations]. / Analiza transferului de oxigen in bioreactoare pentru culturi de fungi. 2. Suspensii de P. chrysogenum asociatii micelare.

Unlike the P. shermanii and S. cerevisiae cultures, the study on the distribution of oxygen transfer in stirred bioreactor for P. chrysogenum pellets broths indicated that this process is controlled mainly by the deposition tendency of the biomass. Similar to the previously studied systems, the analysis of k(1)a distribution indicated its heterogeneity on the bioreactor height, the oxygen transfer rate increasing from position 1 to 4. Contrary to the bacterial and yeasts cultures, the intensification of aeration promoted the initial reduction of k(1)a, which reached a minimum level, followed by its increase, due to the flooding phenomenon.

[Separation of erythromycin by direct pertraction from simulated broths]. / Separarea eritromicinei prin pertractie directa din lichide de fermentatie simulate.

Erythromycin has been separated from simulated broths by free and facilitated pertraction with D2EHPA dissolved in dichloromethane using an U-shaped pertraction cell. The pertraction has been analyzed by means of initial and final mass flows and permeability factor. The main factors which control the pertraction efficiency were identified to be the pH-gradient between the feed and stripping phase, aqueous phases viscosities and mixing intensity.

[Comparative study on separation of p-aminobenzoic and p-hydroxy-benzoic acids by reactive extraction]. / Studiul comparativ al separarii acizilor p-amino- benzoic si p-hidroxibenzoic prin extractie reactiva.

The comparative study on reactive extraction of p-aminobenzoic and p-hydroxybenzoic acid with Amberlite LA-2 and D2EHPA in two solvents with different polarity (n-heptane and dichloromethane) indicated that the nature of the specific substituents, extractant type and solvent polarity control the extraction mechanism. Although the reactive extraction with Amberlite LA-2 of the two acids occurs by means of rather similar interfacial reactions, the extraction with D2EHPA is based on different mechanisms, due to the participation of the two different substituents of aminic and phenolic type. In all cases, the most efficient extractions have been reached for the combination Amberlite LA-2-dichloromethane.

[Selective separation of cinnamic and p-methoxycinnamic acids. The study on reactive extraction from mixture]. / Separarea selectiva a acizilor cinamic si p-metoxicinamic studiul extractiei reactive din amestec.

Cinnamic and p-methoxycinnamic acids have been separated from their mixture by reactive extraction with Amberlite LA-2 dissolved in n-heptane. The efficiency and the selectivity of their separation is controlled by the pH-value and extractant concentration, the optimum conditions being the pH-value of aqueous phase of 2 and the extractant concentration into the organic phase of 10 g/l.

[The extraction and transport of folic acid through liquid membranes]. / Extractia si transportul acidului folic prin membrane lichide.

The study on the extraction and transport of folic acid (vitamin B9) with Amberlite LA-2 underlined the significant influences of the pH-gradient on the aqueous phases, carrier concentration and mixing intensity, in correlation with the extraction mechanism. Thus, for reaching the maximum efficiency of folic acid separation, the pH-value of the initial aqueous phase of 5, the pH-value of the final aqueous solution greater than 11 and the Amberlite LA-2 concentration in solvent layer over 80 g/l are required.

[Separation of vitamins by non-conventional techniques. Facilitated pertraction of vitamin C]. / Separarea vitaminelor prin procedee neconventionale pertractia facilitata a vitaminei C.

Pertraction (permeation through liquid membranes) is one of the new techniques applied for separation and advanced purification of bioactive compounds. The study on the facilitated pertraction of vitamin C with Amberlite LA-2 underlined the significant influences of the pH-gradient between the aqueous phases, carrier concentration and mixing intensity. Thus, for reaching the maximum efficiency of vitamin C pertraction, the pH-value of the initial aqueous phase below 2, the pH-value of the final aqueous solution greater than 11 and the Amberlite LA-2 concentration in solvent layer over 80 g/l are required.

[Methods of advanced purification-the challenge for biosynthetic antibiotics industry]. / Procedee de purificare avansata--provocare pentru industria antibioticelor de biosinteza.

Reactive extraction, permeation through liquid membranes and direct extraction are some of the new techniques applied for separation and advanced purification of biosynthetic antibiotics. Compared with the conventional separation techniques, the main advantages of these extraction methods are: high separation efficiency, the avoidance of antibiotics chemical and thermal inactivation, high purity of obtained antibiotics. Furthermore, using reactive extraction or permeation through liquid membrane, the antibiotics can be selective separated from their biosynthesis precursors or from the secondary biosynthetic compounds. This paper is a review on separation of Penicillins and Erythromycin by means of these extraction techniques, being underlined their advantages, applications and problems concerning the separation process scale-up.