An economic and theoretical yield analysis of C1 carbon sources as alternative substrates in biocatalytic processes

Recently, methane and methanol have garnered attention for their potential to replace sugars as the source of carbon in biocatalytic processes due to their relatively low cost and high abundance.  Despite their low cost, these molecules are not as easily assimilated into biological systems as traditional sugar-based carbon sources.  Additionally, methane and methanol provide much less cellular energy per molecule than glucose or other carbohydrates.  In order to understand the economic viability of using these alternative carbon sources in biocatalysis, we have performed a theoretical yield analysis in the bacteria Escherichia coli, the yeast Saccharomyces cerevisiae, and the cyanobacteria Synecchocus PCC 7002 when grown on methanol, methane, and other well-studied carbon feedstocks.  By comparing theoretical yield and the cost of the carbon source used, we can understand the substrate price ranges that allow for higher profitability using alternative carbon sources in different organisms.  Under current market prices for glucose and methanol, methanol is not a viable substrate economically.  On the other hand, methane could be a more profitable substrate than glucose at current market prices if the slow kinetics of assimilation can be overcome and near theoretical yield can be reached.