Wang X, Conway P L, Brown I L, Evans A J
CRC for Food Industry Innovation at Food Science Australia, Highett, VIC 3190, Australia.
Appl Environ Microbiol. 1999 Nov;65(11):4848-54. doi: 10.1128/AEM.65.11.4848-4854.1999.
It has been well established that a certain amount of ingested starch can escape digestion in the human small intestine and consequently enters the large intestine, where it may serve as a carbon source for bacterial fermentation. Thirty-eight types of human colonic bacteria were screened for their capacity to utilize soluble starch, gelatinized amylopectin maize starch, and high-amylose maize starch granules by measuring the clear zones on starch agar plates. The six cultures which produced clear zones on amylopectin maize starch- containing plates were selected for further studies for utilization of amylopectin maize starch and high-amylose maize starch granules A (amylose; Sigma) and B (Culture Pro 958N). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to detect bacterial starch-degrading enzymes. It was demonstrated that Bifidobacterium spp., Bacteroides spp., Fusobacterium spp., and strains of Eubacterium, Clostridium, Streptococcus, and Propionibacterium could hydrolyze the gelatinized amylopectin maize starch, while only Bifidobacterium spp. and Clostridium butyricum could efficiently utilize high-amylose maize starch granules. In fact, C. butyricum and Bifidobacterium spp. had higher specific growth rates in the autoclaved medium containing high-amylose maize starch granules and hydrolyzed 80 and 40% of the amylose, respectively. Starch-degrading enzymes were cell bound on Bifidobacterium and Bacteroides cells and were extracellular for C. butyricum. Active staining for starch-degrading enzymes on SDS-PAGE gels showed that the Bifidobacterium cells produced several starch-degrading enzymes with high relative molecular (M(r)) weights (>160,000), medium-sized relative molecular weights (>66,000), and low relative molecular weights (<66,000). It was concluded that Bifidobacterium spp. and C. butyricum degraded and utilized granules of amylomaize starch.
业已明确，一定量摄入的淀粉可在人类小肠中逃避消化，进而进入大肠，在大肠中它可作为细菌发酵的碳源。通过测量淀粉琼脂平板上的透明圈，对38种人类结肠细菌利用可溶性淀粉、糊化支链淀粉玉米淀粉和高直链玉米淀粉颗粒的能力进行了筛选。选择在含支链淀粉玉米淀粉平板上产生透明圈的六种培养物，进一步研究其对支链淀粉玉米淀粉和高直链玉米淀粉颗粒A（直链淀粉；Sigma）和B（Culture Pro 958N）的利用情况。采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）检测细菌淀粉降解酶。结果表明，双歧杆菌属、拟杆菌属、梭杆菌属以及真杆菌属、梭菌属、链球菌属和丙酸杆菌属的菌株能够水解糊化的支链淀粉玉米淀粉，而只有双歧杆菌属和丁酸梭菌能够有效利用高直链玉米淀粉颗粒。事实上，丁酸梭菌和双歧杆菌属在含有高直链玉米淀粉颗粒的高压灭菌培养基中具有较高的比生长速率，分别水解了80%和40%的直链淀粉。淀粉降解酶在双歧杆菌和拟杆菌细胞上与细胞结合，而在丁酸梭菌中为胞外酶。SDS-PAGE凝胶上淀粉降解酶的活性染色显示，双歧杆菌细胞产生了几种相对分子质量（M(r)）较高（>160,000）、中等相对分子质量（>66,000）和低相对分子质量（<66,000）的淀粉降解酶。得出的结论是，双歧杆菌属和丁酸梭菌能够降解并利用高直链玉米淀粉颗粒。
