P. Dalev

Utilisation of waste feathers from poultry slaughter for production of a protein concentrate

A combined enzyme-alkaline technology for processing waste feathers from poultry slaughterhouses was elaborated. The enzyme, alkaline proteinase, is produced on a large scale and is used in the food industry. Full solubilisation of feathers was achieved after pretreatment with 0·3 m NaOH solution at 80°C, mechanical disintegration and enzyme hydrolysis at 55–60°C. After spray-drying the end-product was a heavy, greyish powder with a protein content of 795 g kg−1 and with a not unpleasant smell. The high protein content defines the product as a ‘protein concentrate’. Amino acid content proved it of high biological value. The preparation method could lead to the possibility of application in a large-scale production.

Biodegradation of chemically modified gelatin films in lake and river waters

Gelatin was chemically modified by crosslinking samples with one of a number of bifunctional reagents as was done earlier in a processing technique used to improve mechanical properties through chain orientation. The effects of this crosslinking on the biodegradability of the resulting films were evaluated in the laboratory by exposing them to lake and river waters for 10 days with or without inoculation with periphyton organisms. Biodegradabilities were assessed by weight losses of the films and by measurements of dehydrogenase activity of biomasses taken from their surfaces. The extent of biodegradation depended on the type of crosslinking agent and the presence or absence of the periphyton. The gelatin films crosslinked with formaldehyde, glyoxal, or glutaraldehyde were the slowest to biodegrade; complete degradation required 8-10 days. In contrast, the most biodegradable was the gelatin crosslinked with hexamethylene diisocyanate, which required only 3-4 days. The uncrosslinked gelatin and the gelatin crosslinked with butadiene diepoxide and diepoxyoctane were intermediate, degrading in 5-7 days. The dehydrogenase activity paralleled the weight losses but rapidly decreased when the amount of gelatin remaining was small.

Enzymic modification of feather keratin hydrolysates with lysine aimed at increasing the biological value

The lysine content of feather protein hydrolysate was modified via activation with alkaline proteinase and trypsin at pH 6·2 and 8·3, respectively. Lysine was used as the hydrochloride and the diacetyl derivative in the first case and as the methyl ester in the trypsin modification. The results indicate a lysine content of 26–35 g kg-1 and 59–64 g kg-1 after alkaline proteinase activation and 52–65 g kg-1 after trypsin activation. Considerable changes in the molecular mass profile of peptides were observed. Thus, enzyme modification is a way to raise the nutritive value of feather protein hydrolysate by increasing its lysine content (the main limiting essential amino acid).

An enzyme-alkaline hydrolysis of feather keratin for obtaining aprotein concentrate for fodder

ConclusionThe considered procedure for obtaining protein concentrate from feather can be applied for the utilization of waste feathers from the poultry industry.

Biodegradation of chemically modified gelatin films in soil

Gelatin films that had been chemically modified (crosslinked with formaldehyde, glyoxal, glutaraldehyde, hexamethylene diisocyanate, butadiene diepoxide, or diepoxyoctane) were tested for their biodegradability by soil burial testing in a laboratory environment under temperature and humidity control. The relationship between weight loss and time of biodegradation showed a linear behavior for all the samples, but the rate of biodegradation showed a dependence on the type of crosslinking agent. The most stable films were those crosslinked with aldehydes, and these biodegraded by the 10th day. The samples crosslinked with hexamethylene diisocyanate and diepoxides completely biodegraded by the fourth and sixth days, respectively. It was shown that the rate of biodegradation depended on the density of crosslinking, which was calculated by a modified Flory–Rehner equation. The biodegraded samples showed considerable changes in the fingerprint region of FTIR spectra, and, thus, these spectra could be used for evaluation of the soil burial biodegradation of chemically modified gelatin samples.

Enzymatic degradation of formaldehyde-crosslinked gelatin

A general method is proposed for characterizing the enzymatic degradability of formaldehyde-crosslinked gelatin which is simple and uses subtilisin as a readily available, commercial alkaline proteinase. Solubilization of gelatin involved dissolution of species not chemically bonded to the crosslinked network, as well as the soluble fractions resulting to the enzymatic degradation. There was a linear relationship between the complete solubilization time of the gelatin and its exposure time to the formaldehyde crosslinking procedure.

An enzyme biotechnology for the total utilization of leather wastes

SummaryThe isolation of protein and fat fractions from a waste of the leather industry is discussed. This represents the main waste of leather production and gives rise to problems of ecological and economical nature. A middle capacity factory deposits about 30 tones of the so called carrion, a source for the production of about 3 t useful products-protein and fat.

SOLUBILIZATION AND BIODEGRADATION OF CROSS-LINKED GELATINS BY ALKALINE PROTEINASE

This investigation involves the chemical modification of gelatin, a biomaterial which has been widely studied because of its environmental friendliness, its ready availability from waste products, and its biodegradability. The focus was on cross-linking because it has been shown that the mechanical properties of gelatin can be improved by a sequence of processing steps involving cross-linking, swelling, orientation, and, finally, drying in the oriented state. Because cross-linking is required in this technique, the present study characterizes its possible effects on gelatin biodegradability, as gauged by the time required to solubilize the material. A series of cross-linking agents having various alkylene sequence lengths was used. The resulting cross-linked gelatins were relatively insoluble in phosphate buffer (pH = 8.2) at room temperature, but at higher temperatures, they became partially soluble. Full solubilization of cross-linked gelatins was successfully obtained, however, by the action of an alkaline proteinase, specifically subtilisin. Both the rate of the partial solubilization in buffer and the full solubilization with alkaline proteinase showed dependences on the type, concentration, and chain lengths of the cross-linking agent.

Biodegradation of Chemically Modified Gelatin Films in a Simulated Natural Environment

ABSTRACT Modified (crosslinked) gelatin films were prepared using various crosslinking agents: formaldehyde, butadiene diepoxide and hexamethylene diisocyanate. They were evaluated for their biodegradability by exposing them to sewage, which was inoculated with periphyton taken from the bottom and walls of municipal sewage systems. Biodegradability was assessed by weight loss of the films and by means of total dehydrogenase activity of the biomass, taken from the surface of the films. Biodegradation was apparent both in uncrosslinked gelatin and in the crosslinked samples. The gelatin crosslinked with hexamethylene diisocyanate degraded fastest (complete degradation in 5 days), followed by uncrosslinked gelatin and gelatin crosslinked with butadiene diepoxide (complete degradation in 10 days). The most stable was the formaldehyde crosslinked gelatin—complete degradation only in 20 days. The dehydrogenase activity increased rapidly up to the 7th day, and then dropped. It paralleled the biodegradation of gelatin and could be used as a measure of biodegradability of crosslinked gelatin, and probably other biodegradable polymers. The periphyton on the surfaces of the films was found to be molds, actinomyces, yeast and bacteria. Various kinds of algae were observed as well, specifically flint algae, brown algae, blue-green algae, and filamentous green algae.

Utilization of waste whey as a protein source for production of iron proteinate: An antianaemic preparation

Abstract Iron proteinates (metalosates) are very effective preparations for the treatment of acute and chronic iron deficiencies in animals. A technology for the production of iron proteinate was elaborated employing waste-whey proteins. The iron content in the preparation could be varied by altering the pH and the amount of precipitating agent (FeSO 4 ). The formation of iron proteinate was proved by infrared spectra. The absorbance of both CN (1520 cm −1 and 1630 cm −1 ) and of CO stretchings (1100 cm −1 ) indicated the presence of chelate bonds typical of an iron-proteinate molecule. The biological activity of the product obtained was tested on piglets. Preliminary results showed a good effect both on the animal body weight and on the blood indices, after oral application.