Andrieux C, Pacheco E D, Bouchet B, Gallant D, Szylit O
INRA, Jouy en Josas, France.
Br J Nutr. 1992 May;67(3):489-99. doi: 10.1079/bjn19920053.
To study in vivo the contribution of the bacterial flora to amylomaize starch degradation in the rat, germ-free and conventional rats were fed on a diet containing either a normal maize starch or an amylomaize starch. In germ-free rats maize starch was almost totally digested in the small intestine, whereas 40% of the ingested amylomaize starch reached the caecum and 30% was excreted, despite the very high endogenous amylase activity. Study by transmission electron microscopy of germ-free caecal contents showed an endocorrosion of the starch granule. In conventional rats, as in germ-free rats, digestibility of maize starch reached 98% in the small intestine, whereas that of amylomaize starch was only 60%. In the caecum of these rats amylomaize starch was fermented, and this led to a decrease in caecal pH and to formation of short-chain fatty acids (SCFA), especially propionate. Comparison between conventional rats fed on maize starch or amylomaize starch showed that caecal SCFA concentrations during a circadian cycle varied in the same way whereas total SCFA and lactic acid concentrations were much higher in rats fed on amylomaize starch. Amylase (EC 3.2.1.1) activity was similar in the caecal contents of conventional rats whatever the ingested starch. It was lower in conventional than in germ-free rats, but no starch granule remained in the caecum of conventional rats. These results showed that bacterial amylase was more efficient at degrading resistant amylomaize starch than endogenous amylase.
为了在体内研究细菌菌群对大鼠食用的玉米淀粉降解的贡献，给无菌大鼠和普通大鼠喂食含有普通玉米淀粉或直链玉米淀粉的饲料。在无菌大鼠中，玉米淀粉几乎在小肠中完全消化，而尽管内源性淀粉酶活性很高，但摄入的直链玉米淀粉仍有40%到达盲肠，30%被排泄。对无菌大鼠盲肠内容物进行透射电子显微镜研究显示淀粉颗粒有内腐蚀现象。在普通大鼠中，和无菌大鼠一样，玉米淀粉在小肠中的消化率达到98%，而直链玉米淀粉的消化率仅为60%。在这些大鼠的盲肠中，直链玉米淀粉被发酵，这导致盲肠pH值下降并形成短链脂肪酸（SCFA），尤其是丙酸。比较喂食玉米淀粉或直链玉米淀粉的普通大鼠发现，昼夜周期中盲肠SCFA浓度的变化方式相同，而喂食直链玉米淀粉的大鼠中总SCFA和乳酸浓度要高得多。无论摄入何种淀粉，普通大鼠盲肠内容物中的淀粉酶（EC 3.2.1.1）活性相似。普通大鼠的淀粉酶活性低于无菌大鼠，但普通大鼠的盲肠中没有残留淀粉颗粒。这些结果表明，细菌淀粉酶在降解抗性直链玉米淀粉方面比内源性淀粉酶更有效。
