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Related Experiment Videos

Starch utilization by the human large intestinal microflora.

G T Macfarlane, H N Englyst

    The Journal of Applied Bacteriology
    |March 1, 1986
    PubMed
    Summary

    Human gut bacteria efficiently break down starch using extracellular amylase enzymes. These bacteria produce volatile fatty acids, which are potentially absorbable energy sources in the colon.

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    Digestive diseases (Basel, Switzerland)·2010

    Area of Science:

    • Microbiology
    • Gastroenterology
    • Biochemistry

    Background:

    • Amylase activity in human feces is significant, with most being extracellular.
    • Bacterial amylases are crucial for starch breakdown in the gut.
    • Gut bacteria play a key role in digesting dietary components like starch.

    Purpose of the Study:

    • To quantify amylase activity in human feces.
    • To investigate the efficiency of bacterial cell-bound versus soluble amylases.
    • To identify dominant starch-hydrolyzing bacteria in the human gut.

    Main Methods:

    • Measurement of amylase activity in fecal samples.
    • Fractionation of fecal samples to distinguish extracellular and cell-associated activity.
    • Isolation and identification of starch-hydrolyzing bacterial colonies.
    • Analysis of fermentation products (volatile fatty acids, organic acids) from starch by mixed bacterial cultures.

    Main Results:

    • High amylase activity (2-565 units/g) detected in human feces, predominantly extracellular (>92%).
    • Bacterial cell-bound amylases showed higher efficiency in starch degradation compared to soluble forms.
    • Anaerobic starch-hydrolyzing bacteria populations ranged from 1.1 X 10(10) to 3.3 X 10(12) cells/g.
    • Predominant genera identified were Bifidobacterium, Bacteroides, Fusobacterium, and Butyrivibrio.
    • Starch fermentation by mixed gut bacteria produced volatile fatty acids (approx. 60% of utilized starch) and organic acids, with lactate as a transient intermediate.

    Conclusions:

    • Human fecal amylase activity is largely extracellular and bacterial in origin.
    • Bacterial cell-bound amylases are key players in colonic starch digestion.
    • Gut microbiota efficiently ferments starch into absorbable volatile fatty acids, contributing to host energy metabolism.

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