Shi Jingjun, Chen Xi, Yang Ruoxi, Zhao Dan
Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education & Heilongjiang Provincial Key Laboratory of Plant Genetic Engineering and Biological Fermentation Engineering for Cold Region & Key Laboratory of Microbiology, College of Heilongjiang Province & School of Life Sciences, Heilongjiang University, Harbin, Heilongjiang, People's Republic of China.
Appl Biochem Biotechnol. 2025 Mar 26. doi: 10.1007/s12010-025-05231-2.
Pediococcus acidilactici, a generally regarded as safe (GRAS) lactic acid bacteria species, is a desirable microbial mannanase source due to its high bio-safety. P. acidilactici HDM2 isolated from dragon fruit culture was identified according to morphological, physiological, and biochemical characteristics as well as preserved nucleic acid (16S rDNA and rpoA) sequencing. A two-step response surface methodology (RSM) experiment subsequently screened out and then predicted the optimal levels of two factors which significantly affected P. acidilactici HDM2's mannanase production. The maximal enzyme activity reached 97.9 U/mL under the condition of glucose 17.5 g/L and initial pH 4.6. RSM optimization resulted in a 39.3% increase of mannanase yield which was verified by six repeated trials and consequent t-test (P < 0.05). The enhancement of mannanase production was also proved by congo-red dyeing on KGM (konjac glucomannan)-MRS (de Man, Rogosa, and Sharpe) agar. Diameter of clearance zone enlarged from 2.7 to 4.5 cm through RSM. The purified P. acidilactici HDM2 mannanase with a molecular weight of 30 KDa was then applied in fruit juice clarification process. The enzyme exhibited significantly higher clarifying efficiency than commercial mannanase in both yield and clarity for six out of eight fruits, i.e., orange, peach, grape, pear, kiwi, and grapefruit. These results promised the application of P. acidilactici HDM2's mannanase in various especially food-level fields.
嗜酸乳杆菌是一种通常被认为安全（GRAS）的乳酸菌，因其高生物安全性而成为理想的微生物甘露聚糖酶来源。根据形态、生理和生化特征以及保存的核酸（16S rDNA和rpoA）测序，对从火龙果培养物中分离出的嗜酸乳杆菌HDM2进行了鉴定。随后，通过两步响应面法（RSM）实验筛选并预测了两个对嗜酸乳杆菌HDM2甘露聚糖酶产量有显著影响的因素的最佳水平。在葡萄糖17.5 g/L和初始pH 4.6的条件下，最大酶活性达到97.9 U/mL。RSM优化使甘露聚糖酶产量提高了39.3%，这通过六次重复试验和随后的t检验得到验证（P < 0.05）。在魔芋葡甘露聚糖（KGM）-MRS（德氏、罗格斯和夏普）琼脂上进行刚果红染色也证明了甘露聚糖酶产量的提高。通过RSM，透明圈直径从2.7 cm扩大到4.5 cm。然后将纯化的分子量为30 KDa的嗜酸乳杆菌HDM2甘露聚糖酶应用于果汁澄清过程。在八种水果中的六种，即橙子、桃子、葡萄、梨、猕猴桃和葡萄柚中，该酶在产量和澄清度方面均表现出比商业甘露聚糖酶更高的澄清效率。这些结果表明嗜酸乳杆菌HDM2的甘露聚糖酶有望应用于各种特别是食品级领域。
