Aims: The aim of this study was to develop a method for microbial degradation of indigenous keratin wastes and to compare it with a method of alkaline hydrolysis. Methods and Results: Native sheep skin and wool were chosen as a model mixture of collagen and keratin wastes discarded by the leather and fur industries. Suitable conditions were found for hydrolysis of this mixture by four newly isolated thermoactinomycete strains. Another set of experiments was carried out using alkaline hydrolysis of keratin wastes. It was shown that microbial hydrolysates contained predominantly low molecular peptides and amino acids, including essential ones, while the alkaline hydrolysis produced predominantly peptides of higher molecular weight. Conclusion: A simple and a low-cost method was proposed for rapid and effective biodegradation of keratin wastes using Thermoactinomyces strains. Significance and Impact of the Study: The proposed method could find application in agriculture for preparing mixtures containing valuable peptides and amino acids.

The effect of adding alkaline hydrolysate of sheep's wool waste on the chemical and microbiological properties of a park soil (Sofia, Bulgaria) has been assessed in a 9 month laboratory experiment. The waste product contained 75-80% water-soluble materials: peptides, amino acids, salts, dyes, lipids, some carbohydrates, potassium ions, and it seemed likely that the hydrolysate obtained could be used as a harmless and valuable fertilizer in agriculture. It was demonstrated that the organic material positively influenced microbial soil populations and ryegrass growth. As the remaining partially degraded keratin is highly dispersed it should act as a slow release fertilizer thus feeding plants additionally. The results suggest that the wool hydrolysate is beneficial for improving soil characteristics and could successfully be used as alternative biofertilizer. The authors hope that by utilization of the keratin wastes, the environment around leather and fur plants could be influenced positively and that the expense of removing the wastes to controlled landfill sites and part of the expenses for sustaining the latter will be saved.

Suitable conditions were found for hydrolysis of sheep wool by a mixture of potassium hydroxide and some quantities of sodium hydroxide at elevated temperature (120" C) and pressure (2.03 atm). Because of the severe hydrolysis conditions (pH about 12 and high temperature) it is believed that the causes of some related diseases like "mad cow", "swine fever", bovine spongiform encephalopaty, Creutzfeldt-Jakob disease, that are called prions, and are proteins will be destroyed. The hydrolysate obtained is neutralized by orto-phosphoric acid. Beside organic nitrogen, the obtained hydrolysate contains also potassium and phosphate ions and threfore it is proposed this product to be used as fertilizer in the agriculture. Data are supplied showing the positive effect on rye-grass when the soil was additionally enriched with the new fertilizer. The alkaline hydrolysate contains about 75-80% watersoluble materials-peptides, amino acids, salts, dyes, lipids and some carbohydrates. The remaining part consists of insoluble partly degraded keratin. The latter ·is highly dispersed and therefore it is believed that it will be degraded by the soil microorganisms for relatively short time, thus feeding the plants additionally.The authors hope that if this way of utilization of the keratin wastes is used the environment around the leather and fur plants will be influenced positively and that the expenses for carrying away the wastes to controlled dung-hills and part of the expenses for sustaining the latter will be safed.