Università di Torino, Dipartimento di Scienze Agrarie, Forestali e Alimentari, Grugliasco, Torino, Italy.
Department of Food Science, Food Microbiology, Faculty of Science, University of Copenhagen, Denmark.
Int J Food Microbiol. 2015 Jul 16;205:81-9. doi: 10.1016/j.ijfoodmicro.2015.04.011. Epub 2015 Apr 9.
Phytate is known as a strong chelate of minerals causing their reduced uptake by the human intestine. Ninety-three yeast isolates from traditional African fermented food products, belonging to nine species (Pichia kudriavzevii, Saccharomyces cerevisiae, Clavispora lusitaniae, Kluyveromyces marxianus, Millerozyma farinosa, Candida glabrata, Wickerhamomyces anomalus, Hanseniaspora guilliermondii and Debaryomyces nepalensis) were screened for phytase production on solid and liquid media. 95% were able to grow in the presence of phytate as sole phosphate source, P. kudriavzevii being the best growing species. A phytase coding gene of P. kudriavzevii (PHYPk) was identified and its expression was studied during growth by RT-qPCR. The expression level of PHYPk was significantly higher in phytate-medium, compared to phosphate-medium. In phytate-medium expression was seen in the lag phase. Significant differences in gene expression were detected among the strains as well as between the media. A correlation was found between the PHYPk expression and phytase extracellular activity.
植酸是一种很强的矿物质螯合剂，会导致人体肠道对矿物质的吸收减少。从传统非洲发酵食品中筛选出的 93 株酵母分离株，属于 9 个种（毕赤酵母、酿酒酵母、鲁氏接合酵母、马克斯克鲁维酵母、米曲霉、光滑假丝酵母、异常汉逊酵母、毕赤酵母和德巴利酵母），在固体和液体培养基上筛选植酸酶的产生。95%的菌株能够在以植酸为唯一磷源的条件下生长，毕赤酵母是生长最好的菌株。鉴定了毕赤酵母的植酸酶编码基因（PHYPk），并通过 RT-qPCR 研究了其在生长过程中的表达。与磷酸盐培养基相比，PHYPk 在植酸盐培养基中的表达水平显著更高。在植酸盐培养基中，在迟滞期就可以观察到基因表达。菌株之间以及培养基之间的基因表达存在显著差异。发现 PHYPk 表达与植酸酶胞外活性之间存在相关性。
