Pathways could be resulting in the other products as malate, succinate, and
glycerol, which have been reported to be fermentative products of C. reinhardtii.
In contrast, the PFL1 pathway is not active in strain 48F5 because of disruption
of the PFL1 gene (indicated by light gray lines and text, and red crosses near PFL1
and below formate in Fig. 4). Instead, the dark-incubated PFL1 mutant generated
more H 2 , CO 2 , ethanol, and D-lactate than the wild type, while acetate secretion
was reduced. Strain 48F5 also showed reduced in vitro hydrogenase activity and
reduced HYD1 transcript and HYD1 protein levels. The amounts of ADH1 were
almost identical in the wild type and the PFL1 mutant. Red downward arrows
indicate a reduction, green upward arrows indicate an increase, and orange equal
symbols indicate unchanged results. The double upward arrows for D-lactate
indicate a more than twofold increase in this metabolite.
Costa et al. (2015) reported in their study the effect of inoculum concentration
and carbon source to C. reinhardtii, as well as the influence of hybrid system and
coculture (C. reinhardtii and R. capsulatus) on the photofermentative ethanol
production. Maximum ethanol content (19.94 g/L) and productivity (0.17 g/(Lh))
were achieved by hybrid system in which the effluent of C. reinhardtii containing
organic acids was used as substrate to R. capsulatus. The results from this work are
beneficial to comprehend the potentiality of microalgae and photosynthetic bacteria
to synthesize ethanol concerning several strategies such as media composition and
different culture systems (hybrid and cocultivation).
Fig. 4 Fermentative pathways of C. reinhardtii mutant PFL1-deficient strain 48F5
242
R. G. Bastos
glycerol, which have been reported to be fermentative products of C. reinhardtii.
In contrast, the PFL1 pathway is not active in strain 48F5 because of disruption
of the PFL1 gene (indicated by light gray lines and text, and red crosses near PFL1
and below formate in Fig. 4). Instead, the dark-incubated PFL1 mutant generated
more H 2 , CO 2 , ethanol, and D-lactate than the wild type, while acetate secretion
was reduced. Strain 48F5 also showed reduced in vitro hydrogenase activity and
reduced HYD1 transcript and HYD1 protein levels. The amounts of ADH1 were
almost identical in the wild type and the PFL1 mutant. Red downward arrows
indicate a reduction, green upward arrows indicate an increase, and orange equal
symbols indicate unchanged results. The double upward arrows for D-lactate
indicate a more than twofold increase in this metabolite.
Costa et al. (2015) reported in their study the effect of inoculum concentration
and carbon source to C. reinhardtii, as well as the influence of hybrid system and
coculture (C. reinhardtii and R. capsulatus) on the photofermentative ethanol
production. Maximum ethanol content (19.94 g/L) and productivity (0.17 g/(Lh))
were achieved by hybrid system in which the effluent of C. reinhardtii containing
organic acids was used as substrate to R. capsulatus. The results from this work are
beneficial to comprehend the potentiality of microalgae and photosynthetic bacteria
to synthesize ethanol concerning several strategies such as media composition and
different culture systems (hybrid and cocultivation).
Fig. 4 Fermentative pathways of C. reinhardtii mutant PFL1-deficient strain 48F5
242
R. G. Bastos