Optimizing the biodegradation of two keratinous wastes through a Bacillus subtilis recombinant strain using a response surface methodology |
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Authors: | Amira M Embaby Taha I Zaghloul and Ahmed R Elmahdy |
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Institution: | (1) Department of Biotechnology, Institute of Graduate Studies and Research, Alexandria University, 163 El Horreya Aven., EL Chatby, P.O. Box 830, Egypt;(2) Department of Food Science and Technology, Faculty of Agriculture, Alexandria University, Alexandria, Egypt |
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Abstract: | 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 NH2-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 NH2-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 NH2-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 NH2-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 NH2-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 NH2-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. |
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