Blibech M, Farhat-Khemakhem A, Kriaa M, Aslouj R, Boukhris I, Alghamdi OA, Chouayekh H. Optimization of β-mannanase production by Bacillus subtilis US191 using economical agricultural substrates.
Biotechnol Prog 2020;
36:e2989. [PMID:
32134202 DOI:
10.1002/btpr.2989]
[Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 03/02/2020] [Accepted: 03/04/2020] [Indexed: 12/13/2022]
Abstract
The Bacillus subtilis US191 strain producing highly thermostable β-mannanase was previously selected as potential probiotic candidate for application as feed supplement in poultry industry. Initially, the level of extracellular β-mannanase production by this strain was 1.48 U ml-1 . To improve this enzyme titer, the present study was undertaken to optimize the fermentation conditions through experimental designs and valorization of agro-industrial byproducts. Using the Plackett-Burman design, in submerged fermentation, a set of 14 culture variables was evaluated in terms of their effects on β-mannanase production. Locust bean gum (LBG), soymeal, temperature, and inoculum size were subsequently optimized by response surface methodology using Box-Behnken design. Under optimized conditions (1 g L-1 LBG, 8 g L-1 soymeal, temperature of 30°C and inoculum size of 1010 CFU ml-1 ), a 2.59-fold enhancement in β-mannanase titer was achieved. Next, to decrease the enzyme production cost, the effect of partial substitution of LBG (1 g L-1 ) by agro-industrial byproducts was investigated, and a Taguchi design was applied. This allowed the attaining of a β-mannanase production level of 8.75 U ml-1 in presence of 0.25 g L-1 LBG, 5 g L-1 of coffee residue powder, 5 g L-1 of date seeds powder, and 5 g L-1 of prickly pear seeds powder as mannans sources. Overall, a 5.91-fold improvement in β-mannanase production by B. subtilis US191 was achieved.
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