Culture condition optimization of C. curvatus has been
reported in previous research [1,15e17]. However, our
preliminary research found that optimal conditions for C.
curvatus’ growth with acetate as carbon source was significantly
different from that with glucose. For example, pH 5.5 is
usually used in glucose culture, but pH 5.5 with acetate
resulted in poor growth. Therefore, culture conditions with
VFA as carbon sources need to be investigated and optimized.
Furthermore, the hydrogen fermentation process which uses
bacteria produces many metabolites, and some of them may
inhibit yeast growth. Thus, the presence of potential inhibitors
in HPE should be examined. Finally, an actual waste
stream should be tested to prove the feasibility of this entire
waste-to-biofuel process. In this study, optimal pH and
acetate concentration was first determined. To test if inhibitors
were produced in the fermentative hydrogen production
process, sucrose, instead of the actual waste stream, was
tested as surrogate for raw waste material, since pure sucrose
will not introduce any inhibitor into the hydrogen production
process. Finally, food waste was used as an actual example of
potential commercial raw material for dark fermentation
hydrogen production, and the effluent was tested as a feedstock
for lipid production with C. curvatus culture.