Lima Juliana Oliveira, Pereira Jorge Fernando, Araújo Elza Fernandes de, Queiroz Marisa Vieira de
Universidade Federal de Viçosa, Departamento de Microbiologia, Viçosa, MG, Brazil.
Universidade Federal de Viçosa, Departamento de Microbiologia, Viçosa, MG, Brazil; Embrapa Trigo, Passo Fundo, RS, Brazil.
Braz J Microbiol. 2017 Jul-Sep;48(3):602-606. doi: 10.1016/j.bjm.2016.12.009. Epub 2017 Feb 9.
Expression of pectinolytic genes is regulated by catabolic repression limiting the production of pectin lyase (PL) if the natural inducer, pectin, is missing from the growth medium. Here, we report the isolation of Penicillium griseoroseum mutants resistant to 2-deoxy-d-glucose (DG) that show resistance to catabolite repression and overproduce PL. Three spontaneous and nine UV-induced mutants were obtained. Some mutants produced sectors (segments morphologically different) that were also studied. The mutants were analyzed for pectinases production on pectinase-agar plates and five mutants and two sectors showing larger clearing zones than the wild type were selected for quantitative assay. Although PL production higher than the wild type has been found, phenotype instability was observed for most of the mutants and, after transfers to nonselective medium, the DG resistance was no longer present. Only mutants M03 and M04 were stable maintaining the DG-resistance phenotype. When growing for 120h in liquid medium containing glucose with or without pectin, both mutants showed higher PL production. In the presence of glucose as sole carbon source, the mutant M03 produced 7.8-fold more PL than the wild type. Due its phenotypic stability and PL overproduction, the mutant M03 presents potential for industrial applications.
如果生长培养基中缺少天然诱导剂果胶，果胶分解基因的表达会受到分解代谢阻遏的调控，从而限制果胶裂解酶（PL）的产生。在此，我们报道了对2-脱氧-D-葡萄糖（DG）具有抗性的灰玫瑰青霉突变体的分离，这些突变体对分解代谢阻遏具有抗性并过量产生PL。获得了三个自发突变体和九个紫外线诱导的突变体。还对一些产生扇形区域（形态上不同的区段）的突变体进行了研究。在果胶酶琼脂平板上分析突变体的果胶酶产生情况，并选择五个突变体和两个比野生型显示出更大透明圈的扇形区域进行定量测定。虽然发现PL产量高于野生型，但大多数突变体表现出表型不稳定性，转移到非选择性培养基后，对DG的抗性不再存在。只有突变体M03和M04保持稳定，维持对DG的抗性表型。当在含有葡萄糖且有或没有果胶的液体培养基中培养120小时时，这两个突变体均显示出更高的PL产量。在以葡萄糖作为唯一碳源的情况下，突变体M03产生的PL比野生型多7.8倍。由于其表型稳定性和PL过量产生，突变体M03具有工业应用潜力。
