Selection of Rhodobacter sphaeroides P47 as a useful source of single cell protein.

Abstract

Rhodobacter sphaeroides P47 was selected as a potent microorganism for SCP production. The selection criteria were: high growth rate, high growth yield from consumed sugar, ability to consume various sugars, high protein content with a balanced amino acid composition, and acceptable contents of vitamin B12 and carotenoids. When the cells grew aerobically on minimal medium containing glucose, fructose and xylose as sole carbon sources, they grew at the relatively high specific growth rate of 0.12-0.161/hr. Also, the growth yield from sugar, 0.52-0.55g of cells/g of sugar, was high compared with Rb. sphaeroides S as a standard. In the sugar uptake test, strain P47 not only preferably consumed glucose, fructose, xylose and mannose, but also consumed maltose, sucrose, cellobiose and treharose. Strain S consumed only glucose, fructose, xylose and mannose. Strain P47 cells cultured on pineapple waste medium had a relatively high protein content (66.6%) with balanced amino acid composition. The intracellular contents of vitamins B12 and E and carotenoids were 7.9, 21, and 80mg/100g of dry cells, respectively. These values were considerably higher than those of other photosynthetic bacteria.