typically 5-10%: in phytoplankton 20-30% %
||Ashley E. Beck, Kristopher A. Hunt, and Ross P. Carlson, Measuring Cellular Biomass Composition for Computational Biology Applications, Processes 2018, 6(5), 38, doi:10.3390/pr6050038 p.16 bottom paragraph
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||P.16 bottom paragraph: "Experimentally measured biomass composition provides a species-relevant basis for representing cellular growth in computational models. The results of the macromolecular assays for E. coli, Synechococcus 7002, and A. acidocaldarius are summarized in Table 4. The mass percentages for the five assays do not necessarily sum to 100% of cell dry weight. The reduced mass recovery may be due to loss of biomass during centrifugation and transfer of material while performing the assays. Some bacteria may also possess other storage compounds that are not accounted for in these analyses, such as polyhydroxyalkanoates or polyphosphates. Ash weight typically accounts for 5–10% of cell dry weight [primary source 72], or perhaps even more for some organisms (e.g., 20–30% ash content has been measured in phytoplankton [primary source 73]). To adjust for losses during sample processing, measurements can be normalized to the total mass recovered such that the sum of biomass recovered from all measurements is 100% (Table 4)."