Science
Growing waste
Bernard Dixon
IF all available sulphite liquor (effluent from the paper industry), whey (cheese creamery waste), and molasses were used to grow microbes for food, about a twentieth of the world's protein needs would be satisfied. This startling calculation — highlighting the largely unexploited potential of microbes for novel food production — emerged during a seminar, the proceedings of which have now been published, held earlier this year by the Octagon Group at Manchester University.
The Octagon Group is concerned with "the controlled uses of microorganisms for human welfare, and specifically with the technological, economic, and political problems that their large-scale exploitation raises". It brings together people from industry and the universities, and came into being late last year with, as its organisers euphemistically put it, "the rapidly changing patterns of world economy very much in our minds."
Global inflation, the perilous world food situation, the energy and resource crises (epitomised though not initiated by the action of the oil sheikhs a year ago), and the likelihood of increasing exploitation of natural resources for political ends, have all begun to stimulate a reassessment of existing and potential technology. In that context, the contributions which the unseen, teeming world of bacteria, yeasts, fungi and other microbes could make to the relief of our complex plight are outstanding.
Consider, for example, the beauty and economic sense in using what are otherwise waste materials or grossly inconvenient effluents to make (very cheaply indeed) food rich in protein, vitamins, and other nutritional goodies. The Swedes have seen the sense of this idea sooner than most Western countries. The Swedish Sugar Corporation has devised the 'Symba' process, which turns potato waste into animal fodder. The idea is simplicity itself. First, a fungus growing on the waste produces enzymes which convert the starch into glucose. (A similar enzyme in saliva is responsible for the sweet
taste of starch when chewed.) Next, a yeast which cannot subsist on starch, but which manufactures much protein and valuable nutrients, is grown on the glucose.
The Swedish Sugar Corporation produces some 1,000 tons of yeast per year by this process, and sells it as chicken feed. What is especially attractive about the scheme is that the raw material is in ample supply and is an otherwise bothersome pollutant that would have to be rendered inoffensive before being released into the environment. According to Dr Colin Ratledge, who described the system at the Octagon meeting, looked at solely as a method of purifying effluent the process costs at least ten times less per ton of waste than when using conventional methods.
There are innumerable other potential, techniques of this sort, simply awaiting practical development. Dr Ratledge points out that large cream cheeseries produce vast quantities of whey, a waste liquor that contains an appreciable quantity of lactose (milk sugar). There is no use or market for the whey at present. But it too could probably be exploited as a free and abundant starting material for growing microbes. The Milk Marketing Board is currently investigating the possibilities. Similarly, some 80 million tons of bagasse, the waste cellulose from sugar cane processing, are avail able each year. At the moment, bagasse is used for such inefficient and uneconomic purposes as firing boilers. Again, it is theoretically entirely possible to convert the cellulose into food, by turning it first into sugar, and thence into microbial cells that can supplement
human or animal diets. All that is wanted is the practical incentive to move from theory to large-scale practice. "
True, there are snags. Waste materials must be of relatively constant composition if they are to
be used in industrial processes. And some microbial foods produced in
the past have proved to cause , minor digestive troubles. But these difficulties are small compared with similar ones that technologists have already solved in related fields. They are trivial indeed in relation to the global problems that have begun to make microbial food look such an attractive avenue for development.
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