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 rhamnolipid-biosurfactant produced by Pseudomonas sp. PS-17 on cell surface structures of Pseudomonas aeruginosa NBIMCC 1390 was studied. The results demonstrated that the rhamnolipid at concentrations below and above CMC provoked a multi-component response of the bacterial cells without affecting their growth and viability. Above CMC, the rhamnolipid caused reduction of total cellular LPS content of 22%, which can be associated with an increase in cell hydrophobicity to 31% adherence. The rhamnolipid-biosurfactant at concentration below CMC did not affect the LPS component of the bacterial outer membrane but caused changes in OMP composition of P. aeruginosa. Examination of the OMP profiles revealed that the amount of major proteins (Opr F, Opr D, Opr J and Opr M) markedly decreased. To our knowledge this is the first report on the rhamnolipid-biosurfactant interactions with bacterial cells showing changes in outer membrane proteins of P. aeruginosa. In both concentrations, the biosurfactant caused changes in cell surface morphology. The results indicate that the rhamnolipid-biosurfactant from Pseudomonas sp. PS-17 has a potential application in the relatively new field of biomedicine.

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.

In this study, 24 Antarctic bacteria, isolated from sediment and soil samples from Deception and Galindez Islands, were characterized for their antimicrobial activity and response to 13 antibiotics and seven heavy metals. Multiple antibiotic resistance was observed for 67% of sediment isolates and 92% of soil isolates, suggesting medium anthropogenic impact in these Antarctic regions. The results revealed a varying response of the Antarctic bacteria to the tested heavy metals. All isolates showed multiple metal resistance towards two to six heavy metals, with minimum inhibitory concentrations ranging from 1.0 mM to 23.2 mM. The majority of the strains in both groups were resistant to lead, nickel, copper and zinc. Plasmids were detected in 21% of isolates. A consortium of highly metal-resistant bacteria could be developed with potential application for biological treatment of wastewaters. Strains that are highly sensitive to cadmium would be promising for developing biosensors to detect this highly toxic heavy metal in environmental samples. All Antarctic bacteria were found to inhibit the growth of one to all eight of the tested indicator bacteria, and 87% inhibited the growth of one to all four of the yeast indicator cultures. Promising psychrotolerant strains were detected as a valuable source of new antimicrobial compounds.