Prasongsuk Sehanat, Berhow Mark A, Dunlap Christopher A, Weisleder David, Leathers Timothy D, Eveleigh Douglas E, Punnapayak Hunsa
Plant Biomass Utilization Research Unit, Department of Botany, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
J Ind Microbiol Biotechnol. 2007 Jan;34(1):55-61. doi: 10.1007/s10295-006-0163-7. Epub 2006 Aug 15.
Tropical isolates of Aureobasidium pullulans previously isolated from distinct habitats in Thailand were characterized for their capacities to produce the valuable polysaccharide, pullulan. A. pullulans strain NRM2, the so-called "color variant" strain, was the best producer, yielding 25.1 g pullulan l(-1) after 7 days in sucrose medium with peptone as the nitrogen source. Pullulan from strain NRM2 was less pigmented than those from the other strains and was remarkably pure after a simple ethanol precipitation. The molecular weight of pullulan from all cultures dramatically decreased after 3 days growth, as analyzed by high performance size exclusion chromatography. Alpha-amylase with apparent activity against pullulan was expressed constitutively in sucrose-grown cultures and induced in starch-grown cultures. When the alpha-amylase inhibitor acarbose was added to the culture medium, pullulan of slightly higher molecular weight was obtained from late cultures, supporting the notion that alpha-amylase plays a role in the reduction of the molecular weight of pullulan during the production phase.
先前从泰国不同栖息地分离出的热带出芽短梗霉菌株，对其生产有价值的多糖——普鲁兰多糖的能力进行了表征。出芽短梗霉NRM2菌株，即所谓的“颜色变异”菌株，是最佳生产者，在以蛋白胨作为氮源的蔗糖培养基中培养7天后，产率为25.1 g普鲁兰多糖l(-1)。NRM2菌株产生的普鲁兰多糖比其他菌株产生的色素含量少，经过简单的乙醇沉淀后纯度显著提高。通过高效尺寸排阻色谱分析，所有培养物中普鲁兰多糖的分子量在生长3天后显著降低。对普鲁兰多糖具有明显活性的α-淀粉酶在蔗糖培养基中组成型表达，在淀粉培养基中诱导表达。当向培养基中添加α-淀粉酶抑制剂阿卡波糖时，从后期培养物中获得了分子量略高的普鲁兰多糖，这支持了α-淀粉酶在生产阶段对普鲁兰多糖分子量降低起作用的观点。
