Biodegradation of chicken feathers waste directed by Bacillus subtilis recombinant cells: scaling up in a laboratory scale fermentor.

Biodegradation of chicken feathers waste directed by Bacillus subtilis DB 100 (p5.2) cells was successfully carried out in 14L Bio Flo 110 laboratory scale fermentor. Seven liters of feathers-based modified basal medium II, feathers-based tap water and feathers-based distilled water separately in the fermentor were inoculated with activated bacterial cells. The fermentation processes were conducted at 37°C, 700 rpm agitation speed and 0.7 vvm air flow rate in the absence of kanamycin. Highest net levels of released feathers hydrolysis end products [soluble proteins and NH(2)-free amino groups] and keratinolytic alkaline protease activity in the fermentor were greatly comparable to those of shake flasks. Interestingly, the plasmid (p5.2) inside the recombinant B. subtilis cells growing in the fermentor displayed 100% stability till the fifth day of incubation and this presents a great challenge. Data certainly would encourage the transfer to larger scale fermentors to carry out feathers biodegradation process.

Key determinants affecting sheep wool biodegradation directed by a keratinase-producing Bacillus subtilis recombinant strain.

OVAT (one variable at a time) approach was applied in this study to screen the most important physicochemical key determinants involved in the process of sheep wool biodegradation. The process was directed by a keratinase-producing Bacillus subtilis DB 100 (p5.2) recombinant strain. Data indicate that, sheep wool could be degraded efficiently in cultures incubated at 30°C, with initial pH of 7 with agitation at 150 rpm. Two times autoclaved alkali treated and undefatted chopped sheep wool is more accessible to biodegradation. B. subtilis recombinant cells could utilize sheep wool as a sole source of carbon and nitrogen. Sheep wool-based modified basal medium II, lacking NH4Cl and yeast extract, could greatly support the growth of these bacterial cells. Sheep wool biodegradation was conducted efficiently in the absence of kanamycin consequently; high stability of the recombinant plasmid (p5.2) represents a great challenge upon scaling up this process. Three key determinants (sheep wool concentration, incubation time and inoculum size) imposing considerable constraints on the process are highlighted. Sheep wool-based tap water medium and sheep wool-based distilled water medium were formulated in this study. High levels of released end products, produced from sheep wool biodegradation are achieved upon using these two sheep wool-based water media. Data indicate that, sheep wool hydrolysate is rich in some amino acids, such as tyrosine, phenylalanine, lysine, proline, isoleucine, leucine, valine, aspartic acid and glutamic acid. Moreover, the resulting sheep wool hydrolysate contains soluble proteins of high and intermediate molecular weights. The present study demonstrates a feasible, cheap, reproducible, efficient and rapid biotechnological approach towards utilization of raw sheep wool waste through a recombinant bacterium.

Optimizing the biodegradation of two keratinous wastes through a Bacillus subtilis recombinant strain using a response surface methodology.

Statistical optimization of the biodegradation of two keratinous wastes directed by Bacillus subtilis recombinant cells was carried out by means of a response surface methodology. A Box-Behnken design was employed to predict the optimal levels of three variables namely, keratin percent, incubation time and inoculum size. Analysis of variance revealed that, only keratin percent had the highest significant effect. Canonical analysis and ridge max analysis were used to get the optimal levels of the three predictors along with the optimum levels of the responses. The optimal sets of predicted and validated levels of the three variables were [7.69% (w/v) feathers, 96.58 h and 1.28% (v/v) inoculum size] and [8% (w/v) feathers, 98.45 h, 3.9% (v/v) inoculum size] to achieve the highest levels of soluble proteins (1.25-1.7 mg/ml) and NH(2)-free amino groups (245.82-270.0 µmol leucine/ml), respectively upon using three optimized feathers-based media. These values represented 83.67-100% and 100% adequacy for the models of soluble proteins and NH(2)-free amino groups, respectively. While, [8.23% (w/v) sheep wool, 5.52% (v/v) inoculum size and 46.58 h] and [8.33% (w/v) sheep wool, 5.89% (v/v) inoculum size and 63.46 h] were the optimal sets of predicted and validated levels of the above variables to achieve the highest yields of soluble proteins (3.4-4.6 mg/ml) and NH(2)-free amino groups (290.9-302.0 µmol leucine/ml), respectively upon using three optimized sheep wool-based media. These values represented 100% adequacy for the models of soluble proteins and NH(2)-free amino groups. By the end of the optimization strategy, a fold enhancement (2.14-2.43 and 1.78-2.12) in the levels of released soluble proteins and NH(2)-free amino groups, respectively was obtained upon using three optimized feathers-based media. However, a fold enhancement (4.25-5.75 and 2.42-2.5) in the levels of soluble proteins and NH(2)-free amino groups, respectively was obtained upon using three optimized sheep wool-based media. Data would encourage pilot scale optimization of the biodegradation of these wastes.