The concept of eating microorganisms as food is not quite so exotic when we consider that humans have been consuming microorganisms for centuries in such things as bread, wine, yogurt and cheese. But foods such as these won acceptance only after many generations of experimentation and refinement, and, in past centuries, people were unaware of the microbial content as well as the involvement of microorganisms in disease. Today's health-conscious population would probably be more reluctant to sit down to a meal of microbial protein.
Nevertheless, microorganisms may hold a potential solution for relieving growing food shortages. Though microorganisms are not materially a better food source than animals or plants, microorganisms are superior in several respects: a bacterium with a generation time of 30 minutes doubles every half-hour; microorganisms feed on such diverse things as petroleum waste, methanol gas, feathers, and horses' hooves; and, while a thousand-pound steer produces one pound of protein per day, a thousand pounds of bacteria may produce a trillion pounds of protein in the same day.
To allay the fears of consumers, a microbial cell mass used as food is called a single cell protein (SCP). German chemists during World War II were among the first to experiment with SCP. They grew the yeasts Saccharomyces cerevisiae and Candida utilis in the sulfite waste from paper pulp factories and incorporated it into numerous foods. British scientists opted for molasses, and grew yeasts in a commercial plant in Jamaica in 1944. In post-war years, consumer acceptance declined, but yeasts continued to be used in animal feeds.
In the 1950s, Japanese scientists investigated two genera of algae—Chlorella and Scenedesmus—as food sources. The algae were successfully grown in the oxidation lagoons used for sewage treatment and are currently sold in Japan as additives to yogurt, ice cream, and related products. Another alga, Spirulina maxima, has been harvested and consumed by African tribes for centuries. The high protein content of this organism makes it another good candidate for SCP.
Biotechnologists in modern pilot plants are producing enormous quantities of bacteria of the genus Methylophilus in methanol. The bacteria are dried, granulated, and sold as Pruteen for addition to livestock cereals. Methanol-consuming yeasts are used in another product known as Provesteen. Other biotechnologists are investigating fungi as food sources. For example, Trichoderma species digest cellulose and can therefore be cultivated in old newspapers by a paper-to-protein process. Also, Morchella hortensis, a mushroom with a high protein content, has been grown in fermentation tanks and is projected as a possible food source.
As the world continues to approach the limits of crop and animal husbandry, the micro-organisms emerge as a potential answer to the food problem. However, before bacteria burgers become a diet staple, a good deal of salesmanship will be required to overcome the social and psychological stigma of eating microorganisms.
