Department of Food Engineering, Akdeniz University, 07058, Antalya, Turkey.
Biotechnol Lett. 2020 Oct;42(10):1939-1955. doi: 10.1007/s10529-020-02913-1. Epub 2020 May 18.
The fermentation medium contains many complex components (vitamins, minerals, etc.) for better growth of the microorganisms. The increasing purity and number of these components used in the medium seriously affect the cost of the microbial process. This study aimed to further optimize the concentration of the components used in the medium (yeast extract and peptone) for inulinase fabrication by Aspergillus niger from sugar-beet molasses in shake flask fermentation by using Central Composite Design (CCD) and to kinetically identify the fermentation.
The results indicated that the optimal medium composition consisted of only 4.2% (w/v) yeast extract. By using the fermentation environment, the inulinase generation, inulinase/sucrase ratio, maximum inulinase generation rate, maximum sugar depletion rate, and substrate utilization yield were determined as 1294.5 U/mL, 1.2, 159.6 U/mL/day, 7.4 g/L/day, and 98.1%, respectively. The kinetic analysis of the fungal development (logistic model) indicated that a specific development rate and initial biomass concentration were 0.89/day and 1.79 g/L, respectively. Inulinase and sucrase productions are mixed-development associated since the α value ≠ 0 (8.46 and 4.31 U/mgX) and the β value ≠ 0 (5.15 and 4.83 U/mgX day), respectively (Luedeking-Piret model). Besides, the maintenance value (Z) (0.009 gS/gX day) was lower than γ value (1.044 gS/gX), showing that A. niger commonly uses the substrates for enzyme fabrication and fungal development (modified Luedeking-Piret model).
The enzyme activity was increased by optimizing the concentration of the components used. It was demonstrated that the proposed kinetic models can victoriously define fungal development, enzyme fabrication, and sugar depletion.
发酵培养基含有许多复杂成分（维生素、矿物质等），以促进微生物更好地生长。培养基中使用的这些成分的纯度和数量不断增加，严重影响了微生物过程的成本。本研究旨在通过中心组合设计（CCD）进一步优化黑曲霉从糖蜜中发酵生产菊粉酶的培养基（酵母提取物和蛋白胨）中各成分的浓度，并对发酵过程进行动力学鉴定。
结果表明，最佳培养基组成为仅 4.2%（w/v）酵母提取物。利用发酵环境，确定了菊粉酶生成量、菊粉酶/蔗糖酶比值、最大菊粉酶生成速率、最大糖耗速率和底物利用率分别为 1294.5 U/mL、1.2、159.6 U/mL/天、7.4 g/L/天和 98.1%。真菌生长的动力学分析（逻辑模型）表明，特定生长速率和初始生物量浓度分别为 0.89/天和 1.79 g/L。由于α值不等于 0（8.46 和 4.31 U/mgX）和β值不等于 0（5.15 和 4.83 U/mgX 天），因此菊粉酶和蔗糖酶的产生是混合生长相关的（Luedeking-Piret 模型）。此外，维持值（Z）（0.009 gS/gX 天）低于γ值（1.044 gS/gX），表明黑曲霉通常会使用底物来制造酶和真菌生长（改良的 Luedeking-Piret 模型）。
通过优化各成分的浓度提高了酶活性。结果表明，所提出的动力学模型可以成功地定义真菌生长、酶的合成和糖的消耗。
