Feather Hydrolysis Research Articles

Isolation of Bacillus Strains with Keratinolitic Activity

Environmental safety and economic feasibility determine the search for new ways of processing waste in poultry farms. Most of this waste is down and feathers, which are 90% β-keratin. Feathers can be a valuable source of amino acids and peptones when properly processed. The most effective is enzymatic treatment of feather keratin. The search for new strains producing keratinolytic enzymes seems to be a promising direction. On the territory of the poultry farm, 4 strains were isolated from the places of accumulation of feathers. They are able to use chicken feathers as their sole source of organic matter. Based on morphological, genomic, and proteomic analyzes, the isolated strains were identified as Bacillus sp. It was found that the strains secrete proteolytic enzymes that hydrolyze collagen, casein, β-keratin and do not hydrolyze bovine serum albumin. Feather hydrolysis experiments showed that the Bacillus sp. A5.3 possesses maximum keratinolytic activity, and on the second day, the destruction of the second order barbs is observed. The keratinase activity of the strain on azokeratin after an hour of incubation on feather medium was 27.4 U/ml. The optimal conditions for the complex of secreted proteolytic enzymes are pH 7.0-8.0 and temperature 35-40 °C. The isolated Bacillus sp. A5.3 strain is a promising source of proteases and keratinases.

Microbial degradation of poultry feather biomass in a constructed bioreactor and application of hydrolysate as bioenhancer to vegetable crops.

Bioconversion of recalcitrant keratinous biomass is one of the greatest ways to utilize products of feather hydrolysis and recycle them into bionetwork. Present study revealed 87% degradation of poultry feathers within 48 h in a constructed bioreactor using Chryseobacterium sp. RBT. The resulting feather hydrolysate (FH) was rich in soluble protein (3.56 ± 0.18 mg/ml), amino acids (3.83 ± 0.20 mg/ml), and macro and micro nutrients like N (8.0302%), P (0.3876%), K (0.5532%), Cu (0.0684%), Mg (0.8078%), Mn (0.2001%), Ca (0.4832%), Zn (0.0442%), and Fe (0.0330%). HPTLC analysis of FH revealed presence of tryptophan, cysteine, methionine, phenylalanine, glycine, valine, tyrosine, lysine, leucine, and serine as the primary amino acids. Field studies were conducted to apply FH as the bioenhancer to commercially important crops like brinjal and chilli through root drenching (20%, v/v). FH showed positive impact on the growth and development of plants along with early flowering and improved crop yield. In addition, nutritional quality of brinjal and chilli in terms of protein, amino acids, reducing sugars, phenolics, flavonoids, and antioxidant was elevated. Therefore, promotion and utility of by-products generated in feather degradation would be an effective strategy focusing on sustainable agricultural practices and problems associated with the waste management.

Chicken feather and wheat straw hydrolysate for direct utilization in biobutanol production

Lignocellulosic material possesses a source of fermentable saccharides for biofuel production, however it must be supplemented with other nutrients for microbial growth. We have investigated the use of chicken feather as a source of amino acids and peptides. Alkaline hydrolysis of feather under mild conditions (80 °C, 0.6% NaOH) provided a highly solubilized preparation of assimilable nitrogen. Similar conditions were applicable for pre-treatment of wheat straw. The concentration of lignocellulose-derived inhibitors was low so washing or detoxification steps were unnecessary. Therefore, hydrolysis of both materials was carried out simultaneously, resulting in a cultivation medium that was suitable for direct use in biobutanol production. Thirteen strains of solventogenic clostridia were tested for their ability to produce butanol on this mixed hydrolysate; strains of Clostridium beijerinckii and Clostridium saccharoperbutylacetonicum produced the highest butanol concentrations. The proposed process of simultaneous hydrolysis followed by direct inoculation was then demonstrated by experimental production of butanol in a laboratory bioreactor, using C. beijerinckii strain NCIMB 8052 and producing 4.6 g/L of butanol. Although process optimization is still required, we have shown that feather and wheat straw could be co-processed, forming a convenient mixed substrate for biobutanol production.

In vitro pepsin digestibility and amino acid composition in soluble and residual fractions of hydrolyzed chicken feathers

ABSTRACTBeta-keratin in poultry feathers is a structural protein that is resistant to degradation due to disulfide and hydrogen bonds. Feather meal can be a valuable feed compound if the digestibility can be increased. The objective of the present study was to analyze the effects of chemical, enzymatic, and pressure-thermic treatments for chicken feathers on solubility, in vitro protein digestibility (IVPD), and amino acid composition of solubilized and residual fractions. Two experiments were conducted. In experiment 1, models for solubility and IVPD were developed including the above factors applying a central composite face-centered design. Addition of sodium hydroxide (NaOH) and sodium sulfite (Na2SO3), and autoclaving time affected solubility and IVPD of the feather hydrolysates, but not addition of keratinolytic enzyme. In experiment 2, 7 combinations of the hydrolysis factors NaOH, Na2SO3, and autoclaving time with a predicted IVPD of 900 g/kg of DM, calculated for the sum of solubilized and residual feather fractions, were included to measure effects on IVPD and amino acid composition in each fraction. The IVPD values were higher for solubilized than residual fractions when treated with NaOH and autoclaving, but no differences were found when treated with Na2SO3 and autoclaving. Losses of cystine were substantial for all treatments, but lower for Na2SO3 than for NaOH. Furthermore, use of lower Na2SO3 concentration and longer autoclaving time reduced losses of cystine. Compared with NaOH treatments, Na2SO3 gave lower losses of threonine, arginine, serine, and tyrosine. With reference to the ideal protein profile for Atlantic salmon (Salmo salar L.), the treatments with 60 or 90 min autoclaving and 0.36 or 0.21% Na2SO3 had the highest chemical scores. The scores were generally higher for amino acids in residual than solubilized fractions, but with 90 min autoclaving and 0.21% Na2SO3 differences were small. In conclusion, hydrolysis of chicken feathers with low concentrations of Na2SO3 combined with autoclaving results in feather meal with high nutritional value for Atlantic salmon; separation of solubilized and residual fractions is not necessary.

Chicken feather valorization by thermal alkaline pretreatment followed by enzymatic hydrolysis for protein-rich hydrolysate production

A huge amount of feathers is generated as a waste every year. Feathers can be a protein source if it is treated with an appropriate method. The present study investigates feasibility of autoclave alkaline and microwave alkaline pretreatments to be combined with enzymatic treatment for feather solubilization and protein production. Hydrolysis of chicken feather by autoclave alkaline pretreatment followed by an enzymatic method (AAS) or microwave alkaline pretreatment followed by an enzymatic method (MAS) was optimized by response surface methodology. Various NaOH concentrations for autoclave alkaline pretreatment (0.01–0.1 M) and microwave-alkaline pretreatment (0.01–0.05 M) were applied. The holding time for both pretreatments ranged from 1 to 10 min. The pretreated feathers were subjected to enzymatic hydrolysis using a commercial enzyme prior to analysis of protein content, feather solubilization, functional groups, and elemental composition (carbon, hydrogen, nitrogen and sulfur) of the treated feathers. The results revealed that both autoclave alkaline pretreatment and microwave alkaline pretreatment under optimized conditions of 0.068 M NaOH, 2 min holding time, 105 °C and 450 W, 0.05 M NaOH for 10 min, respectively, enhanced the subsequent Savinase hydrolysis of chicken feathers to achieve more than 80% degradation and more than 70% protein recovery. Fourier transform infrared spectroscopy results showed that both thermal-alkaline pretreatments weakened the structure of the feather. Reduction of carbon, nitrogen, and sulfur occurred in both thermal-alkaline pretreatments of feathers indicating degradation of the feather as well as protein release. Thermal-alkaline pretreatment may be a promising method for enhancing the enzymatic hydrolysis of chicken feathers and for producing a protein-rich hydrolysate.

Diseño de Mezclas para la Fabricación de Productos de Mampostería en la Industria Cerámica

En la presente investigación se llevó a cabo la ejecución del ensayo de hidrometría a cinco muestras de arcilla de diferentes tipos de una de las empresas dedicadas a la fabricación de bloques H-10 en la región nortesantandereana con los que se determinaron los porcentajes de arenas, limos y arcillas; los cuales fueron ubicados en el diagrama de Winkler para identificar los tipos de arcillas existentes según su textura y el tipo de producto que se puede fabricar para poder formular una mezcla experimental de material cerámico utilizando el software Statgraphics Centurion XV. Los resultados obtenidos demuestran que las arcillas utilizadas actualmente por la empresa se encuentran en los índices mínimos para la elaboración de bloques H-10 con granulometrías superiores a 2 milímetros de diámetro. Con esta investigación se espera poder pronosticar el comportamiento de las mezcla en las etapas del procesos producto con la condiciones tecnológicas de empresa, con lo que evidentemente se mejoraran los recursos ambientales y económicos de la empresa.

PROTEASE FROM Bacillus sp. AS A DEGRADING CHICKEN FEATHER FOR PRODUCING FEATHER MEAL

Chicken feathers are a significant source of protein for livestock because ofhigh protein content and contain large amounts of cystine, glycine, arginine, and phenylalanine. Chicken feathers are not hydrolyzed, it is very difficult to digest by nonruminant animals because they contain high keratin. Hydrolyzed chicken feathers are not very difficult to digest by nonruminant animals because they contain high keratin. Raw chicken feathers must be hydrolyzed to be used as a feed ingredient for nonruminant species. Processing through bio-fermentation of chicken feathers would lead to overhaul the structure of the network, termination of disulfide bonds,hydrogen bonds and decreased levels of keratin. One of the processing of chicken feathers into feather meal is to utilize the specific proteases that degrade keratin. Bacillus sp. which has been isolated from Kawah Putih crater, Ciwidey, Bandung is a protease-producing bacterium. Fermentation using a medium containing: 2.8% (w/ v) glucose, 0.5% (w / v) urea and 0.005% (w / v) yeast extract with the conditions of the process carried out at pH 7.5; temperature 37 0C; shaker incubator 150 rpm will produce protease with the activity of 121 U / ml and prote in content 6.65 mg /ml in 36 hours. Hydrolysis of chicken feather needs to be pepsin digestibility tested to ensure that it has been processed correctly. Chicken feathers was obtained from slaughterhouses in Bogor. Pepsin digestibility of feather meal after hydrolyzed by proteases from Bacillus sp. is 67.4%.Keywords: feather meal, protease, fermentation, Bacillus sp.

Kinetic study of sulphuric acid hydrolysis of protein feathers.

Poultry feather keratin is the most important by-product from the poultry industry due to its abundance. Different methods have been still applied to process this by-product such as enzymatic hydrolysis which is expensive and inapplicable at the industrial level. This paper presents a study of acid hydrolysis of poultry feathers using different types of acids, sulphuric acid concentration, different temperatures and solid to liquid ratio to obtain a liquid product rich in peptides. The feathers analysis revealed a crude protein content of 88.83%. A maximum peptides production of 676mg/g was reached using sulphuric acid, 1 molar acid concentration and 50g/l solid to liquid ratio at a temperature of 90 °C after 300min. A reaction scheme for protein aggregation and decomposition to polypeptides and amino acids was proposed and a kinetic model for peptides production was developed. The proposed kinetic model proved to be well adapted to the experimental data with R 2=0.99.

Inclusion of exogenous enzymes to feathers during processing on the digestible energy content of feather meal for adult dogs

This study was conducted to determine the coefficient of total tract apparent digestibility (CTTAD) of nutrients and gross energy (GE), metabolizable energy (ME), coefficient of metabolizability of gross energy (CM of GE), and fecal characteristics of dogs fed diets with two levels of feather meal, with or without addition of an enzyme blend containing lipase and protease activity. Ten adult Beagle dogs (aged between 1 and 2 years and weighing 10.2±1.4 kg) were arranged in a 5 × 3 incomplete Latin square design with five treatments and three periods. The extruded basal diet was provided in equal amounts to all dogs (220 g/d), and 7.5 and 15% of hydrolyzed feather meal without enzymes (HFM) or HFM processed with addition of the enzyme blend (HFM EB) was added on top of the basal diet just before feeding. The contrast analysis showed that inclusion of 7.5 or 15% feather meal negatively affected CTTAD of crude protein (CP), GE, and ME of the diets with no apparent effect of the enzyme treatment. However, when both feather meal samples were evaluated, the HFM EB resulted in better CTTAD of GE and CM of GE (0.774 vs. 0.666) than HFM without enzymes (0.670 vs. 0.567), respectively. There was no effect of either feather meal on fecal score. Regression analysis showed that the enzymes added to the feathers during the digestion process increased digestible energy by 600 kcal/kg of dry matter in the diet containing HFM EB. High-performance liquid chromatography (HPLC) analysis demonstrated that feather meal had a low molecular weight, with about 95% of the molecules below 10,000 Da. Addition of enzymes during the feather hydrolysis process may improve the energy content of the feather meal when included in diets for adult dogs.

Feather hydrolysate from Streptomyces sampsonii GS 1322: A potential low cost soil amendment

Process parameters for obtaining hydrolysate from hen feathers, i.e., initial pH (5.0-9.0) and incubation period (1-6 day), were set and studied, using Streptomyces sampsonii GS 1322 in submerged and solid state conditions. Under submerged conditions, complete hydrolysis of feathers was observed on fifth day [initial pH 8.0, 28±2°C, shaking (150rpm)] with release of soluble protein (2985μgml(-1)) and amino acids (2407μgml(-1)). Cell free hydrolysate showed hydrolysis of casein (18mm), gelatin (26mm), collagen (31mm), hemoglobin (23mm) and Tween 80 (35mm) while 445U keratinase activity. Total soluble protein reached 5mgml(-1) in solid state conditions. During Pot experimentation using barren agriculture soil the effect of feather hydrolysate on wheat crop were recorded. Significant increase (p<0.01) in wheat seed germination was observed in treated soils as compared to untreated. Treatment significantly increased plant height from 30 to 60 days and 30-90 days (p<0.001). Treated soil showed an increase in total microbial count, proteolytic activity, phosphate solubilizing bacteria and ammonifying bacteria, whereas pathogenic fungi load was reduced. S.sampsonii GS 1322 can be used for bio-processing of poultry wastes yielding feather hydrolysate rich in proteins and amino acids for development of low-cost organic amendment to accelerate wheat crop growth in barren agricultural land.

Isolation, Identification, and Characterization of a Keratin-degrading Bacterium Chryseobacterium sp. P1-3

In this study, a keratin-degrading bacterium was isolated from soil contaminated with feather waste. The isolated strain was identified as Chryseobacterium sp. P1-3 on the basis of the 16S rRNA gene sequence alignment. Chryseobacterium sp. P1-3 is currently used in various biotechnological applications (e.g., in the hydrolysis of poultry feathers). It hydrolyzed the feather meal within 2 days and possesses a high level of keratinase activity (98 U/mL). The keratinase, partially purified from this strain, prefers casein as a substrate and shows optimal activity at a temperature of 30°C and at a pH of 8.0.

Microwave-enhanced hydrolysis of poultry feather to produce amino acid

Poultry feather was hydrolyzed at relatively mild high temperature ranging from 433 to 473K and autogenous pressure by intensification of microwave heating. The hydrolysate mainly contains arginine, alanine, threonine, glycine, praline, serine, glutamic acid, aspartic acid, cystine and tyrosine, which corresponds with hydrochloric acid catalytic hydrolysis. Based on the orthogonal experimental result, the total yield of amino acid attains about 54.72% with feather containing about 71.83% keratin at optimum reaction condition of temperature 473K, time 20min and weight ratio of water/feather 37.5. The high yield of amino acid and high efficiency of hydrolysis indicate that the microwave has better intensification on hydrolysis comparing with traditional strong acid catalytic or sub-critical hydrolysis. The apparent activation energies (Ea) are 85.12 and 63.00kJ/mol as to the hydrolysis of feather and the degradation of produced amino acid with consecutive pseudo-first-order reaction kinetic model, and the great decrease of the values comparing with non-microwave heating should be the reason of the enhanced effect of microwave.

Influence of the applied pressure of processing upon bioactive components of diets made of feathers

The feathers gained by slaughtering fattening chickens can be processed into protein meal for feeding certain animals, as indicated by its chemical characteristics. However, raw feather proteins (keratin) are faintly digestible (cca. 19%), even inert in digestive tract. Digestion of feather proteins could be improved by hydrolysis (alkaline, enzymatic, microbiological or hydrothermal). Practically, hydrothermal processing of raw feathers is mostly applied. The influence of hydrothermal processing under the pressures of 3.0, 3.5 or 4.0 bar on the nutritive value of the resulting meal is presented in this paper. For the hydrolysis of raw feathers, semi continuous procedure was applied. Semi continuous procedure of feathers processing comprise hydrolysis of raw wet feathers followed by partial drying of hydrolyzed mass that has to be done in a hydrolyser with indirect heating. Continuous tubular dryer with recycled air was used during the final process of drying. Protein nitrogen decreased by 3.46% and 4.80% in comparison with total protein nitrogen content in raw feathers under the pressure of 3.0 and 3.5 bar, respectively. The highest applied hydrolysis pressure caused the greatest loss of protein nitrogen up to 9.52%. Hydrothermal hydrolysis under pressure has increased in vitro protein digestibility significantly. Under pressure of 3.0, 3.5 and 4.0 bar digestibility of proteins increasing from 19.01 to 76.39, 81.71 and 87.03%, respectively. Under pressure of 3.0, 3.5 and 4.0 bar cysteine content decreased from 6.44 to 4.17% (loss 35.25%), 3.94 (loss 38.825%) and to 3.75% (loss 41.77%), respectively. These decreases are statistically significant. It can be concluded that the hydrolysis carried out under the pressure of 3.5 bar, during the period of 25 minutes, and with the content of water in raw feathers of cca. 61% is the optimal technological process for converting raw feathers into diets for certain animal diets.

Biodegradation of keratinous waste by Chryseobacterium sp. RBT isolated from soil contaminated with poultry waste

In the present study, a feather degrading bacterial strain was isolated from poultry waste disposal site, Kolhapur, India. The bacterium was identified as Chryseobacterium sp. RBT using 16S rRNA gene sequence analysis. Chryseobacterium sp. RBT showed rapid hydrolysis of native feathers within 30 h and produced the highest level of keratinase activity (98.3 U/ml). Keratin containing wastes viz. silk, human hair, wool and chicken feathers were tested for keratin degrading ability of the bacterium. Amongst the tested substrates, the Chryseobacterium sp. RBT showed more specificity towards chicken feathers (98.6% degradation) with maximum keratinase activity (98.3 U/ml) and solubilized protein concentration (3.84 mg/ml). Effect of various physico-chemical parameters (temperature, pH, carbon and nitrogen sources) on keratinase production was monitored. The maximum keratinase activity was observed at pH (8.6) and temperature (50 °C). Molasses (1.0% w/v) acted as an inducer and enhanced the keratinolytic activity by two fold, while starch worked as an inhibitor. The goat skin when treated with crude keratinase enzyme (2% v/v), showed complete dehairing within 12 h. Hence, Chryseobacterium sp. RBT shows potential as a candidate for treating the keratinous waste in an ecofriendly manner.

Biodegradation of feather waste by extracellular keratinases and gelatinases from Bacillus spp.

In this study, three feather degrading bacterial strains were isolated from agroindustrial residues from a Brazilian poultry farm. Three Gram-positive, spore-forming, rod-shaped bacteria and were identified as B. subtilis 1271, B. licheniformis 1269 and B. cereus 1268 using biochemical, physiologic and molecular methods. These Bacillus spp. strains grew and produced keratinases and peptidases using chicken feather as the sole source of nitrogen and carbon. B. subtilis 1271 degraded feathers completely after 7days at room temperature and produced the highest levels of keratinase (446Uml(-1)). Feather hydrolysis resulted in the production of serine, glycine, glutamic acid, valine and leucine as the major amino acids. Enzymography and zymography analyses demonstrated that enzymatic extracts from the Bacillus spp. effectively degraded keratin and gelatin substrates as well as, casein, hemoglobin and bovine serum albumin. Zymography showed that B. subtilis 1271 and B. licheniformis 1269 produced peptidases and keratinases in the 15-140kDa range, and B. cereus produced a keratinase of ~200kDa using feathers as the carbon and nitrogen source in culture medium. All peptidases and keratinases observed were inhibited by the serine specific peptidase inhibitor phenylmethylsulfonyl fluoride (PMSF). The optimum assay conditions of temperature and pH for keratinase activity were 40-50°C and pH 10.0 for all strains. For gelatinases the best temperature and pH ranges were 50-70°C and pH 7.0-11. These isolates have potential for the biodegradation of feather wastes and production of proteolytic enzymes using feather as a cheap and eco-friendly substrate.

Biochemical and Molecular Characterization of a New Local Keratinase Producing Pseudomomanas sp., MS21

This study aimed to isolate and identify a new local bacterial strain, able to completely degrade keratin-rich wastes into soluble and useful materials which can be used in many proposes. Bacterial keratinases are of particular interest because of their action on insoluble keratin substrates and generally on a broad range of protein substrates. These enzymes have been studied for de-hairing processes in the leather industry and hydrolysis of feather and keratin. Samples from poultry industry wastes, soil, water, fodder and feather were collected from different places in Jeddah, Saudi Arabia. Each sample was plated on feather meal agar plates containing 5 g L feather as the sole carbon and nitrogen source and 1 the obtained colonies were selected, purified and their growth were detected on skimmed milk agar and feather meal broth media. The well grown isolates on feather meal agar which producing the largest clearing zone on skimmed milk plate were selected for keratinase assays. Out of 23 bacterial isolates, 7 isolates were selected. The best keratinase producing bacterium kera MS21 was selected and identified based on morphological, physiological and some biochemical characteristics. It was recorded as a species belonging to the genus Pseudomonas and identified as Pseudomonas sp. The results of identificatio n were confirmed by 16S rDNA studies. Precipitation and purification of the keratinase enzyme in addition to factors affecting enzyme activity were studied. The enzyme molecular weight was determined to be of 30 KDa using sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. The optimum temperature and pH were determined to be 37°C and pH 8.0, respectively. The effect of some proteases inhibitors and activators were also studied.

Degradation of raw feather by a novel high molecular weight extracellular protease from newly isolated Bacillus cereus DCUW

Biotreatment of feather wastes and utilization of the degraded products in feed and foodstuffs has been a challenge. In the present study, we have demonstrated the degradation of feather waste by Bacillus cereus DCUW strain isolated during a functional screening based microbial diversity study on East Calcutta Wetland Area. A high molecular weight keratinolytic protease from feather degrading DCUW strain was purified and characterized. Moreover, utilization of degraded products during feather hydrolysis was developed and demonstrated. The purified keratinolytic protease was found to show pH and temperature optima of 8.5 and 50 degrees C, respectively. PMSF was found to inhibit the enzyme completely. The purified enzyme showed molecular weight of 80 kDa (from SDS-PAGE). The protease was found to have broad range substrate specificities that include keratin, casein, collagen, fibrin, BAPNA and gelatin. The protease was identified as minor extracellular protease (Vpr) by RT-PCR and northern blotting techniques. This is the first report describing the characterization of minor extracellular protease (Vpr) and its involvement in feather degradation in B. cereus group of organisms.

Production of an extracellular keratinase from Chryseobacterium sp. growing on raw feathers

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.

Recycling of Keratin-containing Materials (Chicken Feather) Through Genetically Engineered Bacteria

Chicken feather is mainly keratin which is not normally degraded by common proteolytic enzymes. It is generated in large quantities as a by-product of poultry processing industry and little is known about its recycling. We reported the biodegradation of chicken feather waste (CFW) by a recombinant Bacillus subtilis strain harboring a multicopy alkaline protease (aprE) gene which acted as a keratinase. In present work, degradation of CFW was greatly enhanced by optimizing several factors. Pretreatment of CFW with NaOH or two times autoclaving enhanced the process. Cultures supplemented, separately, with 0.1% yeast extract or 0.5% corn oil enhanced the degradation of CFW. Biodegradation was optimized when the cultures contained 2% (w/v) CFW, 5% inoculum size, and incubated at 45°C for 3–4 days. Biodegradation was evaluated by monitoring soluble proteins and NH2-free amino groups that were obtained as a result of the enzymatic hydrolysis of feather. Biodegradation of feather waste using these recombinant cells represents an alternative way to improve the nutritional value of feather. Moreover, the release of soluble proteins and amino acids from feather as well as the secreted keratinase enzyme would promote several industries based on feather waste.

English

Eight strains of Bacillus were isolated from non treated soil, characterized and used for the digestion of feather wastes in the laboratory. Non-protein nitrogen (NPN) and total protein (TP) were determined during the incubation time and the microbial counts of the different strains during feather hydrolysis were also monitored. Results of the screening test showed that the solid pieces of feather were completely digested by all the strains. The most efficient isolated strain selected was compared with Bacillus subtilis ATCC 6633. Results showed that the total protein decreased from 13.6% to 1.92 % with the isolated strain, and from 12.25 % to 2.99% with the standard strain. The NPN reached a concentration of 43.2mg/100g and 20.5 mg/100g with the isolated and standard strains, respectively.