Department of Chemical and Biological Engineering/Food Science, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.
Int J Food Microbiol. 2010 Jan 1;136(3):352-8. doi: 10.1016/j.ijfoodmicro.2009.10.011. Epub 2009 Oct 22.
The focus of the present investigation was on the Tanzanian fermented food togwa as a source for dietary iron and zinc, and the potential for mineral availability improvements using selected yeasts. To establish the content of target minerals and main inhibitor for intestinal uptake, iron and zinc as well as the mineral chelating phytic acid, (IP(6) or phytate) were determined in naturally fermented togwa. Yeasts were isolated from sorghum, maize and cassava based togwa, and identified by sequencing the D1/D2 region of the LSU rRNA gene. The isolated yeasts were subsequently screened for phytase activity. The total iron content in sorghum, maize and cassava based togwa were 41.5 (+/-7.2), 85.4 (+/-31.9) and 28.6 (+/-3.8) microg/g dw (dry weight) respectively. The zinc content was 12.3 (+/-3.1), 11.0 (+/-1.1) and 6.4 (+/-4.5) microg/g dw in sorghum, maize and cassava based togwa, and the phytate content in the three varieties were 2.6+/-1.2, 4.7+/-0.8 and 0.4+/-0.4 micromol/g dw respectively. The phytate levels in the sorghum and maize based togwa are expected to substantially reduce the availability of iron. The molar ratio phytate to iron for these two varieties were estimated to be 3.5:1 and 3.1:1 respectively. In general, a phytate to iron molar ratio below 1 is needed to increase the availability of iron. Among 26 isolates, 9 different species could be distinguished: Issatchenkia orientalis, Pichia anomala, Pichia norvegensis, Pichia burtonii, Pichia guilliermondii, Kluyveromyces marxianus, Saccharomyces cerevisiae, Hanseniaspora guilliermondii and Candida glabrata. The strains were screened for phytase activity in YPD supplemented with 0.5 mM IP(6). Of 26 screened strains, the phytase activity was most prominent in strains of I. orientalis and H. guilliermondii. The strains and data constitute a basis for further improvements of iron and zinc bioavailability in togwa.
本研究的重点是坦桑尼亚发酵食品 togwa 作为膳食铁和锌的来源，以及使用选定的酵母提高矿物质可用性的潜力。为了确定目标矿物质的含量和主要的肠道吸收抑制剂，铁和锌以及矿物质螯合植酸（IP（6）或植酸盐），在天然发酵的 togwa 中进行了测定。从高粱、玉米和木薯基 togwa 中分离出酵母，并通过测序 LSU rRNA 基因的 D1/D2 区进行鉴定。随后筛选了分离出的酵母的植酸酶活性。高粱、玉米和木薯基 togwa 的总铁含量分别为 41.5（+/-7.2）、85.4（+/-31.9）和 28.6（+/-3.8）μg/g dw（干重）。锌含量分别为 12.3（+/-3.1）、11.0（+/-1.1）和 6.4（+/-4.5）μg/g dw，三种品种的植酸盐含量分别为 2.6+/-1.2、4.7+/-0.8 和 0.4+/-0.4 μmol/g dw。高粱和玉米基 togwa 中的植酸盐水平预计将大大降低铁的生物利用度。这两种品种的植酸盐与铁的摩尔比估计分别为 3.5:1 和 3.1:1。一般来说，需要植酸盐与铁的摩尔比低于 1 才能提高铁的生物利用度。在 26 个分离株中，可以区分出 9 个不同的种：东方伊萨酵母、异常毕赤酵母、挪威毕赤酵母、 Burton 毕赤酵母、毕赤酵母、马克斯克鲁维酵母、酿酒酵母、汉逊酵母和光滑假丝酵母。在 YPD 培养基中添加 0.5mM IP（6）筛选了这些菌株的植酸酶活性。在 26 株筛选的菌株中，东方伊萨酵母和汉逊酵母的植酸酶活性最为显著。这些菌株和数据为进一步提高 togwa 中铁和锌的生物利用度奠定了基础。
