Department of Soil Science, College of Agricultural Engineering and Technology, University of Tehran, Tehran, Iran.
World J Microbiol Biotechnol. 2012 Jul;28(7):2601-8. doi: 10.1007/s11274-012-1069-3. Epub 2012 May 10.
In this study 97 soil samples from different soil ecosystems were collected. The initial screening was performed on modified glycerol arginine agar (MGAA) to isolate common actinomycetes and on modified MGA-SE (MMGA-SE) to isolate rare actinomycetes. Sixty-seven isolates potentially producing extracellular phytate-degrading activity were identified. The potential to dephosphorylate phytate was confirmed in liquid culture for 46.3 % of the isolates. 12 strains were selected for a direct determination of their phytate-degrading capacity. The results highlighted that the selected isolates produced extracellular phytate-degrading activity; however their capacity in InsP(6) degradation was different. In addition the fermentation medium had an effect on the extent of phytate degradation. Some enzymatic properties of the phytases from isolate No. 43 and isolate No. 63 were determined after obtaining phytase-enriched samples. The enzymes had maximum phytate-degrading capability at 55 °C and pH 5 (isolate No. 43) and 37 °C and pH 7 (isolates No. 63), respectively. Due to their properties, the phytase of isolate No. 43 behaves like a histidine acid phytase, whereas the phytase of No. 63 showed similar enzymatic properties to the phytase of lily. To our knowledge, the results from this study demonstrated for the first time that actinomycetes produce extracellular phytate-degrading activity. By 16SrRNA sequencing, the more closely studied phytase producers were identified as Streptomyces sp. Isolate No. 43 showed 98 % identity to Streptomyces alboniger and S. venezuelae, while isolate No. 63 exhibited 98 % sequence identity to S. ambofaciens and S. lienomycini.
本研究采集了来自不同土壤生态系统的 97 个土壤样本。最初的筛选是在改良的甘油精氨酸琼脂（MGAA）上进行的，以分离常见的放线菌，在改良的 MGA-SE（MMGA-SE）上进行的，以分离罕见的放线菌。鉴定出 67 株具有潜在胞外植酸降解活性的分离株。在液体培养中，有 46.3%的分离株被证实具有去磷酸化植酸的能力。选择了 12 株菌进行植酸降解能力的直接测定。结果表明，所选分离株具有胞外植酸降解活性；然而，它们在 InsP(6)降解中的能力不同。此外，发酵培养基对植酸降解的程度有影响。从 43 号和 63 号分离株获得植酸酶富集样品后，测定了植酸酶的一些酶学性质。在 55°C 和 pH 5（43 号分离株）和 37°C 和 pH 7（63 号分离株）下，酶具有最大的植酸降解能力。由于其特性，43 号分离株的植酸酶表现为组氨酸酸性植酸酶，而 63 号分离株的植酸酶表现出与百合植酸酶相似的酶学性质。据我们所知，本研究的结果首次表明放线菌产生胞外植酸降解活性。通过 16SrRNA 测序，对研究较多的植酸酶产生菌进行了鉴定，43 号分离株与链霉菌属 alboniger 和 S. venezuelae 的同源性为 98%，而 63 号分离株与 S. ambofaciens 和 S. lienomycini 的同源性为 98%。
