Saad Moataza Mahmoud, Saad Abdelnaby Mahmoud, Hassan Helmy Mohamed, Ibrahim Eman I, Abdelraof Mohamed, Ali Basant A
Microbial Chemistry Department, National Research Centre (NRC), 33 Bohouth St, Dokki, 12622, Giza, Egypt.
Bioresour Bioprocess. 2023 Oct 28;10(1):73. doi: 10.1186/s40643-023-00686-9.
Tannases are valuable industrial enzymes used in food, pharmaceutical, cosmetic, leather manufacture and in environmental biotechnology. In this study, 15 fungal isolates were obtained from Egyptian cultivated soil and marine samples. The isolated fungi were qualitatively and quantitatively screened for their abilities to produce tannase. The selected fungal isolate NRC8 giving highest tannase activity was identified by molecular technique (18S rRNA) as Aspergillus glaucus. Among different tannin-containing wastes tested, the black tea waste was the best substrate for tannase production by Aspergillus glaucus in solid-state fermentation (SSF). Optimization of the different process parameters required for maximum enzyme production was carried out to design a suitable SSF process. Maximal tannase production was achieved with moisture content of 75%, an inoculums size of 6 × 10 spore/ml and sodium nitrate 0.2% (pH of 5.0) at 30 °C after 5 days of incubation. Box-Behnken experiment was designed to get a quadratic model for further optimization studies. Four-factor response-surface method with 27 runs was prepared using independent parameters including (moisture content %, initial pH, substrate concentration (g) and sodium nitrate concentration (g) for tannase model. The F- and P-values of the model were 4.30 and 0.002, respectively, which implied that the model is significant. In addition, the lack-of-fit was 1040.37 which indicates the same significance relative to the pure error. A. glaucus tannase was evaluated by the efficiency of conversion of tannic acid to gallic acid. Moreover, production of gallic acid from SSF process of A. glaucus using black tea waste was found to be 38.27 mg/ml. The best bioconversion efficiency was achieved at 40 °C with tannic acid concentration up to 200 g/L.
单宁酶是食品、制药、化妆品、皮革制造及环境生物技术领域中重要的工业用酶。本研究从埃及耕地土壤和海洋样本中分离出15株真菌。对分离得到的真菌进行定性和定量筛选，以检测其产生单宁酶的能力。通过分子技术（18S rRNA）鉴定出具有最高单宁酶活性的所选真菌菌株NRC8为灰绿曲霉。在测试的不同含单宁废弃物中，红茶废弃物是灰绿曲霉固态发酵（SSF）生产单宁酶的最佳底物。为设计合适的固态发酵工艺，对最大酶产量所需的不同工艺参数进行了优化。在30℃培养5天后，水分含量75%、接种量6×10孢子/ml、硝酸钠0.2%（pH 5.0）时可实现最大单宁酶产量。设计Box-Behnken实验以获得二次模型用于进一步优化研究。使用包括（水分含量%、初始pH、底物浓度（g）和硝酸钠浓度（g））的独立参数，为单宁酶模型准备了27次运行的四因素响应面法。该模型的F值和P值分别为4.30和0.002，这表明该模型具有显著性。此外，失拟值为1040.37，这表明相对于纯误差具有相同的显著性。通过单宁酸转化为没食子酸的效率评估了灰绿曲霉单宁酶。此外，发现使用红茶废弃物的灰绿曲霉固态发酵过程中没食子酸的产量为38.27mg/ml。在40℃、单宁酸浓度高达200g/L时实现了最佳生物转化效率。
