Laboratoire de Microorganismes et de Biomolécules, Centre de Biotechnologie de Sfax, Sfax, Tunisia.
Department of Biological Sciences, Faculty of Sciences, University of Jeddah, Jeddah, Kingdom of Saudi Arabia.
Biotechnol Prog. 2020 Jul;36(4):e2989. doi: 10.1002/btpr.2989. Epub 2020 Mar 13.
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 . 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 LBG, 8 g L soymeal, temperature of 30°C and inoculum size of 10 CFU ml ), 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 ) 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 in presence of 0.25 g L LBG, 5 g L of coffee residue powder, 5 g L of date seeds powder, and 5 g L of prickly pear seeds powder as mannans sources. Overall, a 5.91-fold improvement in β-mannanase production by B. subtilis US191 was achieved.
先前已选择产生高度热稳定β-甘露聚糖酶的枯草芽孢杆菌 US191 菌株作为在禽类工业中用作饲料补充的潜在益生菌候选物。最初，该菌株的胞外β-甘露聚糖酶的产量为 1.48 U/ml。为了提高这种酶的效价，本研究通过实验设计和农业工业副产物的增值来优化发酵条件。在浸没发酵中，使用 Plackett-Burman 设计评估了 14 种培养变量，以评估它们对β-甘露聚糖酶生产的影响。随后通过响应面法使用 Box-Behnken 设计对罗望子胶（LBG）、豆粕、温度和接种量进行了优化。在优化条件下（1 g/L LBG、8 g/L 豆粕、温度为 30°C 和接种量为 10 个 CFU/ml），β-甘露聚糖酶的效价提高了 2.59 倍。接下来，为了降低酶的生产成本，研究了部分替代 LBG（1 g/L）的农业工业副产物的效果，并应用了 Taguchi 设计。这使得在存在 0.25 g/L LBG、5 g/L 咖啡渣粉、5 g/L 椰枣籽粉和 5 g/L 仙人掌籽粉作为甘露聚糖源的情况下，β-甘露聚糖酶的产量达到了 8.75 U/ml。总体而言，枯草芽孢杆菌 US191 产生β-甘露聚糖酶的能力提高了 5.91 倍。
