An apparent anomaly in the calculation of ash-free dry weights for the determination of cellular yields

Abstract

The use of ash-free dry weights results in a determination of CHON-containing cell mass that is 5 to 6% less than that determined on the basis of total cellular composition. This discrepancy derives from the fact that phosphorus and sulfur contribute greater weight to ash as oxides and salts of P and S than the contribution they make as part of the cellular fabric. In addition, in the absence of P and S, the unit carbon formula for this mass becomes changed, on the basis of an equivalent number of available electrons per unit of carbon formula weight.