American Journal of Clinical Nutrition, Vol 23, 1508-1513, Copyright © 1970 by The American Society for Clinical Nutrition, Inc.

Energy Metabolism in Anaerobes

¹ From the Department of Animal Science University of California, Davis, California 95616

An analysis of factors affecting fermentation and growth patterns of the anaerobic microbes of the digestive tract was undertaken and, based upon this, estimates of the amounts of nutrients required for microbial growth in the digestive tract were formulated. It is suggested that under ideal conditions—not often found in vivo—for microbial growth in the digestive tract 3.2-3.9 g available nutrient are utilized to produce 1.0 g dry wt of microbes. Forty-nine to 52% of the digestible energy available to the microbes is converted to fermentation products such as acetic, propionic, and butyric acids in obtaining chemical energy (ATP) to support microbial growth and 26-32% is incorporated into microbial cells. It is implied that knowledge of quantitative aspects of anaerobic microbial metabolism and growth, of amounts of nutrients available for microbial use in vivo, and amounts of fermentation products formed in vivo or amounts of microbial growth occurring in vivo, or both, can provide valuable bases for evaluating microbial and microbe-animal interactions and competition for nutrients, and for extending the usefulness of existing data.