Anaerobic digestion, despite its preferable use as a treatment for high organic matter polluted waste streams, is susceptible to inhibitors, salt included. Therefore, two different experiments were conducted to observe the responses of bacterial and archaeal communities to hypersaline environments. In the first experiment, salt was added gradually, while in the second experiment, salt was added rapidly (so-called salt shocks were performed). The results of the gradual addition of salt showed a recovery of methane production after the salt concentration decreased. The NaCl concentration of 28.2 g/L seems to be the limit between stable operation and occurrence inhibition. The specific biogas production varied between 0.490 and 0.562 m³/kg_tCOD during the stepwise salt addition, depending on the salt concentration, while the maximal achieved COD removal was 79.8%. The results of the rapid salt addition showed good recovery of the bacterial community, while a reduction of salt-sensitive species was observed in the archaeal community. The trend of specific biogas production during rapid salt addition was stable with an average value of 0.590 m³/kg_tCOD, and it was observed that higher concentrations of up to 39.4 g/L of NaCl were tolerated. The maximum COD removal achieved during rapid salt addition was 83.1%. In conclusion, certain bacterial and archaeal communities were well-adapted to the hypersaline environment and remained active during the anaerobic digestion of substrates with high salt concentration.

The huge amounts of keratin-rich waste generated daily by various industries, slaughterhouses, and processing plants need to be properly managed. Most keratin degradation-related research focuses on keratin from bird feathers, but a vast minority focuses on keratin from sheep wool, which also presents a serious environmental problem. In this article, we describe the isolation, identification, and characterization of new keratinolytic microorganisms capable of sheep wool degradation from sheep wool and soil enriched with wool keratin. We isolated four bacterial species from the genus Bacillus (B. subtilis, B. altitudinis, B. mycoides, and B. wiedmannii), one streptomycete species Streptomyces coelicoflavus identified by whole genome sequencing, and a fungal species Aphanoascus reticulisporus. In some of the isolated microorganisms, we detected keratinolytic activity for the first time, and for most of them, the ability to degrade sheep wool has not been previously demonstrated. The keratinases of the new isolates are active in a wide range of temperatures (25–85 °C) and pH (6.0–10.0), so all isolates show great potential for further biotechnological use in industry and in various environmental and agricultural applications to reduce and recycle keratin-rich wastes such as sheep wool and waste woollen textiles.

A total of 11 ruminal strains currently assigned to Butyrivibrio fibrisolvens and Pseudobutyrivibrio xylanivorans were cultivated in two different media, rumen fluid containing M2 and short-chain fatty acid (SCFA) containing M330, and their cellular fatty acid methyl esters (FAME) and dimethylacetals (DMA) were analyzed using gas chromatography. A comparison of the FAME/DMA compositions revealed that the difference in SCFA contents in the growth medium induced a pronounced quantitative effect on the cellular branched-chain fatty acid and aldehydes proportions only in the P. xylanivorans strains. This study shows that FAME/DMA analysis is a powerful chemotaxonomic tool in the group of phenotypically similar rumen butyrivibria especially when the influence of the growth medium is evaluated.