Single Cell Protein and the Exploitation of Mutant Algae lacking Cell Walls

Abstract

MICROBIAL cells are potentially attractive sources of protein food, but this usefulness is at present limited, not merely by technical and economic difficulties^1–4, but also because the indigestibility of the cell walls limits the extent to which they can be incorporated directly into human food. Indeed it has been suggested that microbial cells⁵ and the alga Chlorella⁶ cannot be used in human food without removal of the cell walls. For algae, there are two ways of overcoming this difficulty—either the material can be fed to ruminants, or mechanical, chemical or enzymatic techniques⁷ can be used for the fractionation and removal of the cell walls. Enzymatic methods are as yet inefficient and, whereas industrial scale production in Czechoslovakia involves mechanical disruption of the algal cells with Ballotini beads, Japanese commercial production involves chemical extraction. Although all these methods are easy and efficient on a laboratory scale, on an industrial scale problems of fractionation are as formidable as those of cultivation². Furthermore, the cost involved militates against a more general utilization of this food source. There is now evidence that by genetic manipulation it is possible in some instances to overcome these problems posed by the presence of the cell wall.