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.

中文翻译：

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使用经济的农业底物优化枯草芽孢杆菌 US191 的 β-甘露聚糖酶生产。

产生高度热稳定性 β-甘露聚糖酶的枯草芽孢杆菌US191 菌株先前被选为潜在的益生菌候选物，用于在家禽业中用作饲料添加剂。最初，该菌株产生的细胞外 β-甘露聚糖酶水平为 1.48 U ml ^-1. 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品的增值来优化发酵条件。使用 Plackett-Burman 设计，在深层发酵中，评估了一组 14 个培养变量对 β-甘露聚糖酶产生的影响。随后使用 Box-Behnken 设计通过响应面方法优化刺槐豆胶 (LBG)、豆粕、温度和接种量。在优化条件下（1 g L ^-1 LBG，8 g L ^-1豆粕，温度为 30°C，接种量为 10 ¹⁰  CFU ml ^-1)，β-甘露聚糖酶滴度提高了 2.59 倍。接下来，为了降低酶的生产成本，研究了农工副产品部分替代 LBG (1 g L ^-1 )的效果，并应用了田口设计。这允许的8.75üml的β甘露聚糖酶的生产水平的实现^-1在0.25克L-存在^-1 LBG 5克L- ^-1咖啡粉残余物，5克L- ^-1日期种子粉，和5g L ^-1作为甘露聚糖来源的仙人球种子粉。总体而言，枯草芽孢杆菌US191 的β-甘露聚糖酶产量提高了 5.91 倍。