Department of Chemical and Biological Engineering/Food Science Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
Int J Food Microbiol. 2012 Feb 1;153(1-2):73-7. doi: 10.1016/j.ijfoodmicro.2011.10.018. Epub 2011 Nov 4.
The fermented cereal-based gruel togwa is used as weaning food for children in Tanzania. Togwa is rich in minerals but these are often not available for uptake in the human intestine due to natural inhibitors, such as phytate (IP(6)). The yeasts Pichia kudriavzevii TY13, Hanseniaspora guilliermondii TY14 and TY20, isolated from Tanzanian togwa, and selected for high phytase activity in complex yeast medium YPD, were now studied regarding their ability to degrade IP(6) in maize-based model togwa. A modified constitutively high-phytase producing Saccharomyces cerevisiae BY80 and commercial Aspergillus ficuum phytase were included for comparison. In addition, a strain of Lactobacillus plantarum was included in the model-togwa set-up. All yeasts in the study grew and reached final cell density 1.5-2 log units higher than the start value. S. cerevisiae BY80 degraded 85% of the IP(6) in 48 h; the same degradation level as with A. ficuum phytase (89%). Of the togwa-isolated yeasts, P. kudriavzevii TY13 and H. guilliermondii TY14 showed strong phytate degradation in the model-togwa; 95% or more of the initial IP(6) was degraded after 48 h. This corresponds to a remaining level of 0.4 and 0.3μmol IP(6)/g dw. Co-inoculation with L. plantarum did not increase IP(6) degradation. Moreover, fermentation with P. kudriavzevii TY13 yielded a successive increase in inorganic phosphate (P(i)), from 0.7 to 5.4 mM, suggesting a phytase production in TY13 which is fairly insensitive to P(i) repression. The study shows that phytate in a model togwa is available for yeast phytase enzymes, and addresses the importance of strain selection for effectively degrading the phytate. Certain yeasts originating from togwa seem to have developed a natural high phytase production, and P. kudriavzevii TY13 and H. guilliermondii TY14 seem particularly well adapted to phytate degradation in togwa, and is our choice for further studies and strain improvement.
发酵的以谷物为基础的粥状 togwa 被用作坦桑尼亚儿童的断奶食品。 togwa 富含矿物质，但由于天然抑制剂（如植酸（IP(6)））的存在，这些矿物质通常无法被人体肠道吸收。从坦桑尼亚 togwa 中分离出来的毕赤酵母 Pichia kudriavzevii TY13、汉逊酵母 Hanseniaspora guilliermondii TY14 和 TY20，以及在复杂酵母培养基 YPD 中具有高植酸酶活性的选择，现被用于研究它们在玉米为基础的模型 togwa 中降解 IP(6)的能力。为了比较，还包括了一株改良的组成型高植酸酶产生酿酒酵母 BY80 和商业 Aspergillus ficuum 植酸酶。此外，在模型 togwa 中还包括了一株植物乳杆菌。在研究中，所有酵母都生长并达到最终细胞密度，比起始值高 1.5-2 个对数单位。酿酒酵母 BY80 在 48 小时内降解了 85%的 IP(6)；与 Aspergillus ficuum 植酸酶（89%）相同的降解水平。在从 togwa 中分离出来的酵母中，P. kudriavzevii TY13 和 H. guilliermondii TY14 在模型 togwa 中表现出强烈的植酸降解能力；48 小时后，初始 IP(6)的 95%或更多被降解。这相当于剩余的 IP(6)水平为 0.4 和 0.3μmol/g dw。与植物乳杆菌共同接种并没有增加 IP(6)的降解。此外，用 P. kudriavzevii TY13 发酵导致无机磷酸盐（P(i)）的连续增加，从 0.7 增加到 5.4 mM，表明 TY13 中存在一种植酸酶的产生，这种酶对 P(i)的抑制作用相当不敏感。该研究表明，模型 togwa 中的植酸可被酵母植酸酶酶降解，并强调了菌株选择对有效降解植酸的重要性。某些来自 togwa 的酵母似乎已经发展出一种天然的高植酸酶产生能力，而 P. kudriavzevii TY13 和 H. guilliermondii TY14 似乎特别适应于 togwa 中的植酸降解，是我们进一步研究和菌株改良的选择。
