Lara Carla A, Santos Renata O, Cadete Raquel M, Ferreira Carla, Marques Susana, Gírio Francisco, Oliveira Evelyn S, Rosa Carlos A, Fonseca César
Departamento de Alimentos, Faculdade de Farmácia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, 31270-901, Brazil.
Antonie Van Leeuwenhoek. 2014 Jun;105(6):1107-19. doi: 10.1007/s10482-014-0172-x. Epub 2014 Apr 19.
In this study, yeasts associated with lignocellulosic materials in Brazil, including decaying wood and sugarcane bagasse, were isolated, and their ability to produce xylanolytic enzymes was investigated. A total of 358 yeast isolates were obtained, with 198 strains isolated from decaying wood and 160 strains isolated from decaying sugarcane bagasse samples. Seventy-five isolates possessed xylanase activity in solid medium and were identified as belonging to nine species: Candida intermedia, C. tropicalis, Meyerozyma guilliermondii, Scheffersomyces shehatae, Sugiyamaella smithiae, Cryptococcus diffluens, Cr. heveanensis, Cr. laurentii and Trichosporon mycotoxinivorans. Twenty-one isolates were further screened for total xylanase activity in liquid medium with xylan, and five xylanolytic yeasts were selected for further characterization, which included quantitative analysis of growth in xylan and xylose and xylanase and β-D-xylosidase activities. The yeasts showing the highest growth rate and cell density in xylan, Cr. laurentii UFMG-HB-48, Su. smithiae UFMG-HM-80.1 and Sc. shehatae UFMG-HM-9.1a, were, simultaneously, those exhibiting higher xylanase activity. Xylan induced the highest level of (extracellular) xylanase activity in Cr. laurentii UFMG-HB-48 and the highest level of (intracellular, extracellular and membrane-associated) β-D-xylosidase activity in Su. smithiae UFMG-HM-80.1. Also, significant β-D-xylosidase levels were detected in xylan-induced cultures of Cr. laurentii UFMG-HB-48 and Sc. shehatae UFMG-HM-9.1a, mainly in extracellular and intracellular spaces, respectively. Under xylose induction, Cr. laurentii UFMG-HB-48 showed the highest intracellular β-D-xylosidase activity among all the yeast tested. C. tropicalis UFMG-HB 93a showed its higher (intracellular) β-D-xylosidase activity under xylose induction and higher at 30 °C than at 50 °C. This study revealed different xylanolytic abilities and strategies in yeasts to metabolise xylan and/or its hydrolysis products (xylo-oligosaccharides and xylose). Xylanolytic yeasts are able to secrete xylanolytic enzymes mainly when induced by xylan and present different strategies (intra- and/or extracellular hydrolysis) for the metabolism of xylo-oligosaccharides. Some of the unique xylanolytic traits identified here should be further explored for their applicability in specific biotechnological processes.
在本研究中，分离了巴西与木质纤维素材料（包括腐朽木材和甘蔗渣）相关的酵母，并研究了它们产生木聚糖分解酶的能力。共获得358株酵母分离株，其中198株从腐朽木材中分离，160株从腐朽甘蔗渣样品中分离。75株分离株在固体培养基中具有木聚糖酶活性，被鉴定为属于9个物种：中间假丝酵母、热带假丝酵母、季也蒙毕赤酵母、嗜热栖热孢酵母、斯氏苏糖酵母、扩散隐球菌、橡胶隐球菌、罗伦隐球菌和抗真菌毒素丝孢酵母。进一步在含有木聚糖的液体培养基中筛选21株分离株的总木聚糖酶活性，选择5株木聚糖分解酵母进行进一步表征，包括对木聚糖和木糖生长以及木聚糖酶和β - D - 木糖苷酶活性的定量分析。在木聚糖中显示出最高生长速率和细胞密度的酵母，即罗伦隐球菌UFMG - HB - 48、斯氏苏糖酵母UFMG - HM - 80.1和嗜热栖热孢酵母UFMG - HM - 9.1a，同时也是木聚糖酶活性较高的酵母。木聚糖在罗伦隐球菌UFMG - HB - 48中诱导出最高水平的（细胞外）木聚糖酶活性，在斯氏苏糖酵母UFMG - HM - 80.1中诱导出最高水平的（细胞内、细胞外和膜相关）β - D - 木糖苷酶活性。此外，在木聚糖诱导的罗伦隐球菌UFMG - HB - 48和嗜热栖热孢酵母UFMG - HM - 9.1a培养物中检测到显著的β - D - 木糖苷酶水平，主要分别存在于细胞外和细胞内空间。在木糖诱导下，罗伦隐球菌UFMG - HB - 48在所有测试酵母中显示出最高的细胞内β - D - 木糖苷酶活性。热带假丝酵母UFMG - HB 93a在木糖诱导下显示出较高的（细胞内）β - D - 木糖苷酶活性，且在30℃时比在50℃时更高。本研究揭示了酵母在代谢木聚糖和/或其水解产物（木寡糖和木糖）方面不同的木聚糖分解能力和策略。木聚糖分解酵母主要在木聚糖诱导时能够分泌木聚糖分解酶，并呈现出不同的（细胞内和/或细胞外水解）策略用于木寡糖的代谢。这里鉴定出的一些独特的木聚糖分解特性应进一步探索其在特定生物技术过程中的适用性。
