Kosciow Konrad, Domin Claudia, Schweiger Paul, Deppenmeier Uwe
Institute of Microbiology and Biotechnology, University of Bonn, Meckenheimer Allee 168, 53115, Bonn, Germany.
Biology Department, Missouri State University, 901 S. National Ave, Springfield, MO, 65897, USA.
J Ind Microbiol Biotechnol. 2016 Jul;43(7):989-99. doi: 10.1007/s10295-016-1770-6. Epub 2016 Apr 20.
Gluconobacter (G.) oxydans strains have great industrial potential due to their ability to incompletely oxidize a wide range of carbohydrates. But there is one major limitation preventing their full production potential. Hydrolysis of polysaccharides is not possible because extracellular hydrolases are not encoded in the genome of Gluconobacter species. Therefore, as a first step for the generation of exoenzyme producing G. oxydans, a leaky outer membrane mutant was created by deleting the TolB encoding gene gox1687. As a second step the xynA gene encoding an endo-1,4-β-xylanase from Bacillus subtilis was expressed in G. oxydans ΔtolB. More than 70 % of the total XynA activity (0.91 mmol h(-1) l culture(-1)) was detected in the culture supernatant of the TolB mutant and only 10 % of endoxylanase activity was observed in the supernatant of G. oxydans xynA. These results showed that a G. oxydans strain with an increased substrate spectrum that is able to use the renewable polysaccharide xylan as a substrate to produce the prebiotic compounds xylobiose and xylooligosaccharides was generated. This is the first report about the combination of the process of incomplete oxidation with the degradation of renewable organic materials from plants for the production of value-added products.
氧化葡萄糖杆菌（Gluconobacter，G.）菌株因其能够不完全氧化多种碳水化合物而具有巨大的工业潜力。但存在一个主要限制因素阻碍了它们的全部生产潜力。由于氧化葡萄糖杆菌属的基因组中未编码细胞外水解酶，因此无法进行多糖的水解。因此，作为产生能分泌胞外酶的氧化葡萄糖杆菌的第一步，通过缺失编码TolB的基因gox1687构建了一个外膜渗漏突变体。第二步，在氧化葡萄糖杆菌ΔtolB中表达了来自枯草芽孢杆菌的编码内切-1,4-β-木聚糖酶的xynA基因。在TolB突变体的培养上清液中检测到超过70%的总XynA活性（0.91 mmol h⁻¹ l培养物⁻¹），而在氧化葡萄糖杆菌xynA的上清液中仅观察到10%的内切木聚糖酶活性。这些结果表明，构建出了一种底物谱增加的氧化葡萄糖杆菌菌株，它能够利用可再生多糖木聚糖作为底物来生产益生元化合物木二糖和木寡糖。这是关于不完全氧化过程与植物可再生有机材料降解相结合以生产增值产品的首次报道。
