Biomass densities attained after 3-days of growth in the AP as a function of HTL temperature and dilution are illustrated in Fig. 4-a and summarized in Fig. 4-b confirming the hypothesis that higher biomass productivity could, in fact, be attained by recycling the AP of HTL than with the standard growth medium. These findings also confirm that G. sulphuraria can be successfully grown heterotrophically on recycled AP.