Trujillo-Roldán M A, Moreno S, Espín G, Galindo E
Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, 62250, Cuernavaca, Morelos, México.
Appl Microbiol Biotechnol. 2004 Feb;63(6):742-7. doi: 10.1007/s00253-003-1419-z. Epub 2003 Aug 20.
An Azotobacter vinelandii mutant lacking alginate-lyase (SML2) and the wild type (ATCC 9046) were used to discriminate between the roles of the polymerase complex and alginate-lyase in the synthesis of alginate in cultures conducted under controlled dissolved oxygen tension (DOT). To avoid the presence of pre-synthesized alginates, all cultures were inoculated with washed cells. For cultures carried out at 3% DOT using the mutant, a well defined family of alginates of high mean molecular weight (MMW) were obtained (985 kDa). Under 1% and 5% DOT, the mutant produced unique families of alginates with lower MMW (150 and 388 kDa). A similar behavior was observed using the wild type: a production of well defined families of alginates of high MMW at 3% DOT (1,250 kDa) and lower MMW at 1% and 5% DOT (370 and 350 kDa). At the end of the ATCC 9046 fermentations, alginate was depolymerized by the action of lyases. Overall, the evidence indicated that polymerization of alginate is carried out by producing families of polysaccharide in a narrow MMW range, and that it is highly dependent on DOT. The role of alginate-lyase (present in the wild type) is restricted to a post-polymerization step.
使用一株缺乏藻酸盐裂解酶（SML2）的维涅兰德固氮菌突变体和野生型（ATCC 9046），以区分在受控溶解氧张力（DOT）条件下培养时，聚合酶复合物和藻酸盐裂解酶在藻酸盐合成中的作用。为避免存在预合成的藻酸盐，所有培养物均接种洗涤过的细胞。对于使用该突变体在3% DOT条件下进行的培养，获得了一系列分子量分布明确的高平均分子量（MMW）藻酸盐（985 kDa）。在1%和5% DOT条件下，该突变体产生了具有较低MMW的独特藻酸盐家族（150和388 kDa）。使用野生型时观察到了类似的行为：在3% DOT条件下产生了分子量分布明确的高MMW藻酸盐家族（1250 kDa），在1%和5% DOT条件下产生了较低MMW的藻酸盐家族（370和350 kDa）。在ATCC 9046发酵结束时，藻酸盐在裂解酶的作用下解聚。总体而言，证据表明藻酸盐的聚合是通过产生一系列分子量范围狭窄的多糖来进行的，并且高度依赖于DOT。藻酸盐裂解酶（存在于野生型中）的作用仅限于聚合后步骤。
