Amino acids recovery

Using the described extraction system, we developed methods of amino acid recovery from pharmaceutical samples and fermentation broth. Amino acids were extracted efficiently from the diluted solution of fermentation broth into [C4Cilm][PFg] in the presence of DC18C6 and may be well back-extracted by the alkaline aqueous solution (pH > 9). These methods served as a basis for the corresponding analytical procedures. 

Additional factors that may affect the reliability of the chemical scoring methods lie with the inherent difficulties of amino acid analysis. The analytical procedure for amino acid analysis can affect both the recovery and reliable quantitation of amino acids. Proteins must first be hydrolyzed to amino acids before analysis. Hydrolysis methods affect the amino acid recovery. Cystine, methionine, tryptophan, threonine, serine, and tyrosinecan bedestroyed during hydrolysis. Valine and isoleucine are released slowly and may not be completely... 

Although GC has been demonstrated to yield accurate results, it is still relatively little used compared to HPLC. This is largely for practical reasons relating to the derivatization procedures necessary for GC. Derivatization kinetics differ from one amino acid to another. Thus, individual amino acid recoveries are highly dependent on the exact reaction time and conditions. Highly experienced analysts are necessary for good precision. 

As a practical matter in the food industry, total amino acid analysis is achieved by the parallel application of several techniques. Then the overall amino acid profile is achieved as a retrospective composite of the results from these techniques. The general acid hydrolysis mentioned earlier yields acceptable results for most of the amino acids. Recoveries for serine, threonine, valine, leucine, and isoleucine tend to be a bit low (85-95%) but are usually tolerable. Glutamine and glutamic acid are determined together as Glx. Similarly, asparagine and aspartic acid are codetermined as Asx. 

There have been many studies for the optimization of conditions for the standard acid hydrolysis, but only a few of the more recent examples (24,27-29) are referenced here. These studies address the influence of various hydrolysis parameters on the accuracy of amino acid recoveries. Topics include acid-to-protein ratio, hydrolysis time, hydrolysis temperature, and the use of sealed tubes vs. open reflux. There is also evidence of a wide variety of techniques for the deaeration (very important ) of the sample, including vacuum, nitrogen purging, freeze/thawing, and combinations thereof. All of these issues have already been thoroughly reviewed in earlier... 

M Rudemo, S Bech-Andersen, VC Mason. Hydrolysate preparation for amino acid determinations in feed constituents. 5. The influence of hydrolysis time on amino acid recovery. Z Tierphysiol Tierernaehr Futtermittelkd 43 27-34, 1980. 

The recoveries of first-cycle residues typically result in sequencing initial yields ranging from 10%-50% of the total amount of sample applied to the Zitex membrane. As observed for amino-terminal sequencing, there is a sample and residue-specific dependency that contribute to the initial thiohydantoin-amino acid recoveries. The proteins are retained on the Zitex membrane after sequencing (and resist extraction) as determined by the amino acid analysis of the membrane-bound samples. 

Liquid membrane systems were first introduced in 1968 (34), and since then they have been evaluated for various chemical and biochemical applications (35). Some of the applications include the selective extraction of hydrocarbons (36), the recovery of rare earths from process streams (37), the extraction of organic contaminants like phenol from water streams (38), and amino acid recovery (39). 

Amino Acid Recovery Using Liquid Emulsion Membranes... 

Hydrolysis and subsequent amino acid analysis can be used to determine the composition of a protein as well as quantify concentration. Essential to the methodology is the initial hydrolysis step during which the peptide bonds are broken under acidic conditions at high temperatures to generate free amino acids. Conventional protein hydrolysis is typically performed with 6 N HCl at 110 °C for 24 h. The first published study on the use of microwave heating for acid hydrolysis of proteins appeared in 1987, ribonuclease A and insulin B being used as substrates. Solutions were heated in a domestic microwave oven for periods of 1 to 7 min. Amino acid recoveries after heating for 3,4, and 5 min corresponded... 

FIGURE 9.4 A comparison of amino acid recoveries after hydrolysis using microwave-mediated hydrolysis and conventional hydrolysis methods for the protein beta-casein. (Reproduced with permission from Sandoval, W. N. Pham, V. C. Lill, J. R. Drug Discov. Today 2008,13, 1075-1081. Copyright Elsevier.)... 

Rodriguez, O., Madeira, P.P. Macedo, E.A. (2007). Amino-acid recovery using ionic liquids Partitioning in water+ionic liquid systems. Proceedings of European Congress of Chemical Engineering (ECCE-6) Copenhagen, 16-20 September 2007. 

When nuclease was incubated with 100 equiv. of BNPS-skatole in 50% acetic acid for 28 hours, cleavage at the tryptophanyl peptide bond occurred in addition to modification. The released COOH-terminal nonapeptide was identified as a single spot on paper electrophoresis and from the amino acid recovery on the analyzer. The yield of cleavage product was estimated as approximately 15%. No additional peptides were released by cleavage at any other site in the sequence on the basis of analysis by electrophoresis. 

Biomolecule Separations. Advances in chemical separation techniques such as capillary zone electrophoresis (cze) and sedimentation field flow fractionation (sfff) allow for the isolation of nanogram quantities of amino acids and proteins, as weU as the characterization of large biomolecules (63—68) (see Biopolymers, analytical techniques). The two aforementioned techniques, as weU as chromatography and centrifugation, ate all based upon the differential migration of materials. Trends in the area of separations are toward the manipulation of smaller sample volumes, more rapid purification and analysis of materials, higher resolution of complex mixtures, milder conditions, and higher recovery (69). 

Ion exchange (electrostatic) Equihbrium Deionization Water softening Rare earth separations Recovery and separation of pharmaceuticals (e.g., amino acids, proteins)... 

Recovery 93% from amino acid test mixture. b Recovery 100.6% from amino acid test mixture. e Recovery 99.2% from amino acid test mixture. d Decarboxylase-CO method (108, 106). 

In this chapter we consider amino acid production by fermentation and by chemo-enzymatic methods. We first consider the stereochemistry of amino adds and the importance of chirality in chemical synthesis. General approaches to amino add fermentation and recovery of amino adds from fermentation broths are then dealt with, followed by a detailed consideration of the production of L-phenylalanine by direct fermentation. Later in this chapter, chemo-enzymatic methods of amino acid... 

For economical reasons the fermentation time should be as short as possible with a high yield of the amino acid at the end. A second reason not to continue the fermentation in the late stationary phase is the appearance of contaminant-products, which are often difficult to get rid off during the recovery stage. In general, a relatively short lag phase helps to achieve this. The lag phase can be shortened by using a higher concentration of seed inoculum. The seed is produced by growing the production strain in flasks and smaller fermenters. The volume of the seed inoculum is limited, as a rule of tumb normally 10% of the fermentation volume, to prevent dilution problems. 

Recovery of the amino acid from the fermentation broth... 

Recent development of the use of reversed micelles (aqueous surfactant aggregates in organic solvents) to solubilize significant quantities of nonpolar materials within their polar cores can be exploited in the development of new concepts for the continuous selective concentration and recovery of heavy metal ions from dilute aqueous streams. The ability of reversed micelle solutions to extract proteins and amino acids selectively from aqueous media has been recently demonstrated the results indicate that strong electrostatic interactions are the primary basis for selectivity. The high charge-to-surface ratio of the valuable heavy metal ions suggests that they too should be extractable from dilute aqueous solutions. 

Granulocyte colony stimulating factor 127 amino acids E. coll Adjunct to cancer chemotherapy Approved for sale By stimulating white blood cell formation, aids recovery... 

---