Native Gelatin Research Articles

Efficient production of artificially designed gelatins with a Bacillus brevis system.

Artificially designed gelatins comprising tandemly repeated 30-amino-acid peptide units derived from human alphaI collagen were successfully produced with a Bacillus brevis system. The DNA encoding the peptide unit was synthesized by taking into consideration the codon usage of the host cells, but no clones having a tandemly repeated gene were obtained through the above-mentioned strategy. Minirepeat genes could be selected in vivo from a mixture of every possible sequence encoding an artificial gelatin by randomly ligating the mixed sequence unit and transforming it into Escherichia coli. Larger repeat genes constructed by connecting minirepeat genes obtained by in vivo selection were also stable in the expression host cells. Gelatins derived from the eight-unit and six-unit repeat genes were extracellularly produced at the level of 0.5 g/liter and easily purified by ammonium sulfate fractionation and anion-exchange chromatography. The purified artificial gelatins had the predicted N-terminal sequences and amino acid compositions and a solgel property similar to that of the native gelatin. These results suggest that the selection of a repeat unit sequence stable in an expression host is a shortcut for the efficient production of repetitive proteins and that it can conveniently be achieved by the in vivo selection method. This study revealed the possible industrial application of artificially designed repetitive proteins.

Bioadhesion of gelatin films crosslinked with glutaraldehyde.

The present study was carried out in an attempt to make a gelatin film strongly bioadhesive by introducing free dangling aldehyde groups. When gelatin films were treated with 0.5M of glutaraldehyde (GA) solution at 60 degrees C, free aldehyde groups (up to 150 micromol/g) were introduced in the film. The bonding strength of GA-crosslinked gelatin films (GA gelatin films) with biological tissue was assessed using porcine skins. It was found that bonding strength increased with increasing aldehyde content in the film. The GA gelatin films had bonding strength as high as 250 gf/cm2 whereas the native gelatin film (before GA treatment) showed bonding strength of 40 gf/cm2. When the aldehyde groups introduced in the gelatin films were quenched with glycine or reduced by NaBH4, the films no longer demonstrated such high bonding strength. These facts suggest that a Schiff base was formed between the free dangling aldehyde in the GA gelatin films and the amino groups of the natural tissue, which strongly contributed to a marked bioadhesion.

Lipase-catalysed stereoselective esterifications using gelatin-based hydrogels

A hydrogel stable in an organic solvent has been developed. This pseudo-solid aqueous gel (PAG) consists of only native gelatin and water, and has been used for immobilization of enzymes. A relatively high amount of gelatin is required in order to obtain stable gels. PAGs containing the enzyme Candida antarctica lipase (SP 525) were successfully used in catalysing the esterification of R/S-(±)-2-octanol and hexanoic acid in hexane. The conversions as well as the enantiomeric excess values of the product, R-(−)-2-octyl hexanoate, were high and comparable to those obtained with microemulsion-based gels. The PAGs containing immobilized lipase gave reproducible results and may be re-used several times. The gels are easy to prepare and use, non-toxic and biocompatible. The PAGs retain their integrity in organic solvents and may be used in preparative-scale synthesis of organic compounds.

Emulsification and Foaming Properties of Hydrophobically Modified Gelatin

Abstract Surface active gelatins were formed by covalent attachment of hydrophobic groups to gelatin molecules by reacting N -hydroxysuccinimide esters of various fatty acids (C 4 –C 16 ) with the lysine groups. The surface activity was evaluated by emulsification and foaming properties, and by adsorption at the oil–water interface. It was found that, in general, the modified gelatins are more surface active than the native gelatin. The increase in hydrophobic chain length and the number of attached alkyl chains per gelatin molecule leads to a decrease in the emulsion droplet's size and to more stable emulsions. Adsorption isotherms, at the o/w interface, show much higher surface concentration, at saturation, of the modified gelatin than the native gelatin. The modified gelatins also have high foaming ability and a high foam stability, while the maximal foam activity is obtained by the C 8 modified gelatin. The foaming properties of the surface-active gelatins were also compared to that of sodium dodecyl sulfate (SDS) and it was found that below the CMC of SDS, both foam activity and stability were higher for the modified gelatins. On the other hand, above the CMC the foam activity of SDS was higher, but the foam stability was lower than for C 8 –C 16 -modified gelatins.

Formation of Surface Active Gelatin by Covalent Attachment of Hydrophobic Chains

Surface active gelatin was formed by covalent attachment of hydrophobic groups to gelatin molecules. The modification was carried out at various degrees of attachment and with various chain lengths. These modified gelatins (MGs) were synthesized in dry DMSO by a simple and rapid method. The new method leads to high yields and allows high degrees of modification. The MGs, which have various hydrophobicities, have better surface activity than the native gelatin, as determined by surface tension reduction. The surface tension reduction is correlated to the hydrophobicity of the modified molecule, which was determined by a fluorescent probe. It appears that both the increase in the number of the hydrophobic groups and the increase in the chain lengths lead to decreased surface tension. Copyright 1997 Academic Press. Copyright 1997Academic Press

Investigations on Oxidized Gelatins

AbstractStarting from a native, inert bone gelatine three gelatins differing in the degree of oxidation were prepared. Photographic tests indicated an increase in fog and reduced grain growth restraining power with increasing degree of oxidation. Oxidation does not change the aldehyde concentration, but it reduces the gold-binding capacity and lowers the concentration of methionine and of tyrosine and causes hydroxylation of proline to hydroxyproline. Ornithine has been detected in all gelatins, while cysteine was found absent with the usual analytical methodes. The latter, however, has been found in a hydrolyzate prepared from bones. Addition small amounts of cysteine to an oxidized gelatin restores the properties to values similar to those of the initial native gelatin. Therefore, it is assumed that the native gelatin could contain small, not-detectable traces of cysteine which have been oxidized by the hydrogen peroxide treatment.