The biological hydrogen production from amino acids obtained by protein degradation was comprehensively
investigated to increase heating value conversion efficiency. The five amino acids (i.e., alanine, serine,
aspartic acid, arginine, and leucine) produced limited hydrogen (0.2–16.2 mL/g) but abundant soluble
metabolic products (40.1–84.0 mM) during dark-fermentation. The carbon conversion efficiencies of alanine
(85.3%) and serine (94.1%) during dark-fermentation were significantly higher than those of other
amino acids. Residual dark-fermentation solutions treated with zeolite for NH4
+ removal were inoculated
with photosynthetic bacteria to further produce hydrogen during photo-fermentation. The hydrogen
yields of alanine and serine through combined dark- and photo-fermentation were 418.6 and
270.2 mL/g, respectively. The heating value conversion efficiency of alanine to hydrogen was 25.1%,
which was higher than that of serine (21.2%).
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