The later organic acids have been identified as resulting from the proteolytic fermentation of aminoacids
by anaerobic bacteria, particularly from L-leucine and L-valine, with
the production of CO2 [45–47]. Their production might have contributed to the higher amount of CO2 detected in the fermentations
by LE37 or including LE37 (Table 1). Conversely, C. butyricum
achieved a high H2 production with all the microalgal loads tested
with a simultaneous high H2/CO2 ratio. In spite of the need of carrying out the fermentation under aseptic conditions, pure cultures
are more predictable than mixed cultures in terms of co-produced
metabolites passible of further upgrading.