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Optimization of β‐mannanase production by Bacillus subtilis US191 using economical agricultural substrates
Author(s) -
Blibech Monia,
FarhatKhemakhem Ameny,
Kriaa Mouna,
Aslouj Rania,
Boukhris Ines,
Alghamdi Othman A.,
Chouayekh Hichem
Publication year - 2020
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1002/btpr.2989
Subject(s) - locust bean gum , bacillus subtilis , food science , box–behnken design , response surface methodology , fermentation , chemistry , food industry , microbiology and biotechnology , biology , chromatography , materials science , bacteria , xanthan gum , rheology , composite material , genetics
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 10 10 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.