ABSTRACT
The aim of this study was to characterize keratinolytic bacteria isolated from feather waste. Four isolates were selected after growth on solid medium with feather meal as sole carbon and nitrogen source and screened for proteolytic activity on milk agar plates. Three isolates were Gram-negative (belonged to the genera Burkholderia, Chryseobacterium and Pseudomonas) and one was Gram-positive (Microbacterium sp.). These bacteria grew on diverse keratin wastes such as feather meal, raw feathers, chicken nails, hair and wool. Keratinase activity was detected during growth, but the complete degradation of these substrates was not always achieved. The proteolytic character of crude enzymes was assessed using azokeratin and azocasein as substrates. The keratinases were active on both substrates and were similar in keratin hydrolysis when compared with commercially available microbial peptidases. These novel keratinolytic isolates have potential biotechnological use in processes involving keratin hydrolysis.
O objetivo deste estudo foi caracterizar bactérias queratinolíticas isoladas resíduos de penas. Quatro isolados foram selecionados após crescimento em meio sólido contendo farinha de pena como única fonte de carbono e nitrogênio e avaliados quanto a atividade proteolítica em placas de ágar leite. Foram identificadas três linhagens Gram-negativas (pertencentes aos gêneros Burkholderia, Chryseobacterium e Pseudomonas) e uma Gram-positiva (Microbacterium sp.). Estas bactérias cresceram em vários resíduos queratinosos como farinha de pena, penas de frango, unhas de frango, pelos e lã. A atividade queratinolítica foi observada durante crescimento, mas a degradação completa dos substratos não foi observada em todos os casos. O caráter proteolítico das enzimas foi determinado usando azoqueratina e azocaseína como substratos. As queratinases foram ativas em ambos substratos e apresentaram hidrólise de queratina comparável a peptidases microbianas disponíveis comercialmente. Estes novos isolados queratinolíticos apresentam potencial uso biotecnológico em processos relacionados com hidrólise de queratina.
Subject(s)
Gram-Negative Bacteria/isolation & purification , Gram-Positive Bacteria/isolation & purification , In Vitro Techniques , Keratins , Peptide Hydrolases , Poultry , Clinical Enzyme Tests , MethodsABSTRACT
The strain Chryseobacterium sp. kr6 shown to be useful for biotechnological purposes such as hydrolysis of poultry feathers and de-hairing of bovine pelts. The effect of temperature, initial pH and media composition on protease production by this keratinolytic strain was studied. The enzyme was produced between 25 and 37ºC, with maximum activity and yield at 30ºC. When protease production was tested in media with different initial pH, maximum activity was observed when cultivation was carried out at 30ºC and initial pH ranging from 6.0 to 8.0. Higher activity was observed when feathers or feather meal were used as growth substrates, followed by soybean meal. The addition of carbohydrates or surfactants to feather broth resulted in decrease in keratinolytic activity.