Figure 1.
Mixed‐acid fermentation (MAF) of E. coli (A) and use of purple non‐sulfur bacteria (B) in photofermentation (PF) of organic acids (OAs) into H2. The organic acids are taken up by (e.g.) R. sphaeroides, and reducing power is generated as NADH (not shown). This reducing power can either be used for polyhydroxybutyrate synthesis or growth to maintain cellular redox or alternatively can be used for H2 production under light when growth is restricted by limitation of N or P source. Italicized bottlenecks are those overcome by use of the dual system (see text).