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- Potential use of wool-associated Bacillus species for biodegradation of keratinous materialsPublication . Queiroga, A. Catarina; Pintado, Manuela E.; Malcata, F. XavierFive wool-degrading bacterial strains were selected from a set of 115 isolates from a less conventional source, i.e., the wool of Portuguese Merino sheep, based on their promising keratinolytic abilities. All selected strains belong to the genus Bacillus, probably Bacillus subtilis/licheniformis, according to 16S rRNA sequencing. They were able to grow on and hydrolyse feathers and wool (in both native and milled forms), and human hair and nails to a lesser extent. The maximum keratinase activity was recorded on milled chicken feathers. Biodegradation of such keratin-rich matrices increased the amount of soluble proteins in the fermentation broth and implied the action of extracellular enzymes from those adventitious microorganisms. Therefore, such novel strains have a potential for effective use in solid waste management strategies encompassing keratin-rich materials based on submerged fermentation. Concomitantly, the nutritional value of the broth may be improved for eventual formulation of animal feed.
- Use of response surface methodology to optimize protease synthesis by a novel strain of Bacillus sp. isolated from Portuguese sheep woolPublication . Queiroga, A.C.; Pintado, M.E.; Malcata, F.X.Aims: To investigate the influence of yeast extract, peptone, temperature and pH upon protease productivity by Bacillus sp. HTS102 – a novel wild strain isolated from wool of a Portuguese sheep breed (Merino). Methods and Results: A 24 full factorial, central composite design together with response surface methodology was used to carry out the experiments and analyse the results, respectively. Among the individual parameters tested, temperature and peptone concentration produced significant effects upon protease productivity. A high correlation coefficient (R2 = 0Æ994, P < 0Æ01) indicated that the empiric second-order polynomial model postulated was adequate to predict said productivity, with the optimum loci characterized by: temperature of 43 C, peptone content of 1Æ4 g l)1, pH of 5Æ1 and yeast extract concentration of 10Æ0 g l)1. Conclusions: Protease synthesis depends chiefly on temperature and peptone level. The maximum protease activity was more than twice that obtained with the basal medium, so the experimental design and analysis undertaken were effective towards process optimization. Significance and Impact of the Study: Rational choice of processing conditions for maximum protease productivity will be relevant if an economically feasible fermentation process based on Bacillus sp. HTS102 is intended.
- Search for novel proteolytic enzymes aimed at textile and agro-industrial applications: an overview of current and novel approachesPublication . Queiroga, A. Catarina; Pintado, Manuela E.; Malcata, F. XavierThe types and sources of proteolytic enzymes, enzyme assays, strategies for fermentation yield improvement, and novel proteases and their applications in industrial sectors are widely covered in this review. We give a special focus on alkaline proteases for the textile and detergent industries, as well as for the degradation of keratin-rich wastes.
- Wool-associated proteolytic bacteria, isolated from Portuguese Merino breedPublication . Queiroga, A. Catarina; Pintado, Manuela E.; Malcata, F. XavierThe main purpose of this study was to isolate and briefly characterize proteolytic bacteria from a poorly known habitat - raw wool. Fleece samples were accordingly collected from Merino raw wool - a Portuguese ewe breed, at three distinct areas of their body, from animals exhibiting no symptoms or signs of abnormalities: they were then subjected to enumeration and isolation of a total of 158 bacterial strains. Said isolates were screened for protease activity, using the spot technique, on Calcium Caseinate Agar containing 1% (w/v) skim milk. The 36 isolates displaying the highest protease activity underwent a more refined assessment of enzymatic performance - by examining their cell-free supernatant extracts, using casein as substrate. Two Bacillus isolates were eventually chosen owing to their highest proteolytic activities (24.6 and 15.9 U/mL), and identified using molecular biology tools.
- Novel microbial-mediated modifications of wooPublication . Queiroga, A. Catarina; Pintado, M. E.; Malcata, F. XavierA total of 158 microbial strains, previously isolated from raw wool samples of Portuguese Merino breed of sheep, were screened for extracellular protease activity. The 12 isolates with the highest overall activity were further tested via incubation in nutrient broth, and assaying of cell-free supernatants using casein as substrate protein. The cell-free supernatants of the three isolates exhibiting the best performance were finally tested on knitted wool using bursting strength and area shrinkage as quantitative parameters, and microstructure using scanning electron microscopy as qualitative parameter, to conclude on their putative role upon the fiber features. The aforementioned three isolates produced lower weight loss and area shrinkage than those brought about by a commercial reference enzyme under similar operating conditions, without significantly loosing bursting strength.