In vitro degradation of keratin by two species of Bacillus.

Abstract

Keratinolytic microbes represent an important component of soil biocenosis where they mineralize a highly resistant proteinaceous substrate "keratin" of vertebrate skin and its adnexes. Most research on the biodegradation of keratin has been carried out with dermatophytic (Deshmukh and Agrawal, 1985;Evans and Hose, 1975;Kunert, 1989) and nondermatophytic (Rajak et al., 1991(Rajak et al., , 1992 fungi and actinomycetes (Kunert, 1989;Noval and Nickerson, 1959), and the work with bacterial species has been little. The results obtained by Noval and Nickerson (1959) and Kunert (1989) with Streptomyces fradiae revealed that the degradation of hard keratins is due not only to extracellular protease (keratinase); it is always accompanied by the denaturation of keratin substrate by direct reduction, proteolysis, and finally by the marked alkalinization of the medium. The biochemical mechanism of keratin degradation by bacteria also centers on three interlinked processes: denaturation of the substrate, proteolysis, and deamination. The more important bacteria involved in the degradation of wool and other animal fibers include Bacillus putrificus, B. subtilis, B. cereus, and B. mesentericus.In the present paper, an in vitro degradation of keratin substrates by a strain of B. subtilis and two strains of Bacillus licheniformis has been studied. Materials and MethodsMicroorganisms. B. subtilis S1 (MTCC 2616) and B. licheniformis S21 (MTCC 2617) and S23 (MTCC 2618) were recovered from the soils of gelatin factory campus, Jabalpur, and were maintained on glucosepeptone-agar slants at 28Ϯ1°C.Substrate sterilization. Child's scalp hair, cow horn, cow hooves, and human nails were sterilized by the procedure described by Evans and Hose (1975). Inoculum. A loopful from 10-day-old culture of test organism was added to sterilized distilled water, and 1 ml of this inoculum was aseptically transferred to sterile basal salt medium divided into three sets.( i ) Keratin control: 200 mg of keratin substrate ϩ50 ml of medium. (ii) Bacterial control: 1 ml of inoculumϩ50 ml of medium. (iii) Test samples: 200 mg of keratin substrate ϩ50 ml of mediumϩ1 ml of inoculum. All flasks were incubated under stationary conditions at 28Ϯ1°C for 28 days in triplicates.Analysis. Aliquots were removed at the end of each incubation period through preweighed Whatman filter paper No. 42. The culture filtrate was centrifuged at 3,000 rpm for 5 min, and the supernatant was subjected to various biochemical tests.( i ) Determination of pH: Changes in the alkalinity of the culture filtrate was recorded weekly (7, 14, 21, 28 days) (Received May 17, 1999; Accepted November 12, 1999) The ability of two species of Bacillus to degrade child's scalp hair, cow horn, cow hooves, and human nails in vitro under static conditions was studied by the determination of soluble sulphhydryl compounds as cysteine, disulphides as cystine, and release of extracellular keratinase along with changes in alkalinity of the culture filtrate. Child's scalp hair was found to be the most ...

Purification and Characterisation of Keratinase from a Thermotolerant Feather-degrading Bacterium

“…However, the induction of keratinolytic enzyme produced by the species of Bacillus with feather powder, human hair and nails, and cow horn and hooves was reported (Cheng et al 1995;Lal et al 1999). The keratinase production from B. licheniformis FK 14 reached a maximum in the late logarithmic growth phase similar to those reported by Lin et al (1992), Sangali & Brandelli (2000b) and Kim et al (2001).…”

“…Bacillus species have been reported to produce keratinolytic protease (Lin et al 1992;Altalo & Gashe 1993;Cheng et al 1995;Lal et al 1999;Lin et al 1999;Kim et al 2001;Lee et al 2002). However, this strain isolated from Thai soil grew and degraded feather well at elevated temperatures.…”

Purification and characterization of keratinase from a new Bacillus subtilis strain

“…Accompanied by feather degradation and keratinase production, the pH value of the culture increased to about 8.5. B. subtilis strains had been widely utilized for enzyme production, including the keratinases (Lal et al, 1999;Suh and Lee, 2001;Kim et al, 2001;Macedo et al, 2005). Other Bacillus species including B. licheniformis, B. pumilis, B. cereus, B. halodurans and B. pseudofirmus (Williams et al, 1990;Takami et al, 1999;Rozs et al, 2001;Kim et al, 2001;Gessesse et al, 2003;El-Refai et al, 2005) had also been reported for their keratinolytic activity.…”

Biodegradation of Hard Keratins by Two Bacillus Strains

“…Moreover, maximum keratinase production was recorded after eight days of culture. Likewise, one of the strains inquired by Lal et al (19), B. licheniformis S23, exhibited great capability of human hair decomposition, especially in prolonged cultures. Maximum keratinase activity was obtained after one month of cultivation and the amount of reduced thiols reached nearly 0.3 mM, proving strains keratinolytic action against hair, in contrast to cow hoove or horn and human nail material.…”