314
P. Prabakaran et al.
higher sugar concentrations (Kalnenieks et al. 2014). Yang et al. (2016) summarized
that Z. mobilis was able to utilize glucose, sucrose, and fructose to produce bioethanol.
For instance, a production of 78 g/L of bioethanol under batch fermentation (pH 6
and 32 °C) with an initial carbon content of 295 g/L; 20.5 g/L of bioethanol from
60 g/L of xylose; 72 g/L of bioethanol from 150 g/L of fructose under continuous
fermentation with immobilized cells (pH 5 and 30 °C); and 87.2 g/L of bioethanol
from sucrose (350 g/L) under repeated batch fermentation with immobilized cells
(pH 4 and 30 °C).
8 Products Recovery
The commercial production of bioethanol required a product recovery process (Balat
et al. 2008). The bioethanol can be recovered from distillation process, where
the bioethanol distillate is concentrated (~37%) below the azeotrope in distillation
column, whereas the bottom product is discharged to stripping column to remove
excessive water, and the remaining bioethanol was recycled back to the feed. The
recovery of bioethanol process can be controlled at 99.6% to minimize the lost. On
the other hand, the solids product from the fermentation process was separated by
a centrifuge, followed by drying process in rotary dryer. Then, the solids products
are recovered in the evaporation process as clean condensate and concentrated syrup
(15–20% of total solids weight).
9 Conclusion
Microalgae biomass is the third generation feedstock for biofuel production. Besides
the accumulation of lipid within the microalgae cells for biodiesel production, the
stored carbohydrate also can be further utilized for bioethanol production. It is foreseen that bioethanol derived from microalgae biomass could pave a sustainable route
to substitute the gasoline in the global market. However, more researches are still
required to justify the commercial feasibility of microalgae bioethanol production,
especially the life cycle impact assessment and techno-economic analysis.
Acknowledgements We gratefully acknowledge RUSA—Phase 2.0 grant sanctioned vide Letter
No.F.24-51/2014-U, Policy (TN Multi-Gen), Dept. of Edn. Govt. of India, Dated 09.10.2018 and
financial assistance rendered to Ms. N. Rashiya in the form of a UGC – RGNF by University Grants
Commission, New Delhi [No. F1 – 17.1/2014-15/RGNF-2014-15-SC-TAM-75166].
P. Prabakaran et al.
higher sugar concentrations (Kalnenieks et al. 2014). Yang et al. (2016) summarized
that Z. mobilis was able to utilize glucose, sucrose, and fructose to produce bioethanol.
For instance, a production of 78 g/L of bioethanol under batch fermentation (pH 6
and 32 °C) with an initial carbon content of 295 g/L; 20.5 g/L of bioethanol from
60 g/L of xylose; 72 g/L of bioethanol from 150 g/L of fructose under continuous
fermentation with immobilized cells (pH 5 and 30 °C); and 87.2 g/L of bioethanol
from sucrose (350 g/L) under repeated batch fermentation with immobilized cells
(pH 4 and 30 °C).
8 Products Recovery
The commercial production of bioethanol required a product recovery process (Balat
et al. 2008). The bioethanol can be recovered from distillation process, where
the bioethanol distillate is concentrated (~37%) below the azeotrope in distillation
column, whereas the bottom product is discharged to stripping column to remove
excessive water, and the remaining bioethanol was recycled back to the feed. The
recovery of bioethanol process can be controlled at 99.6% to minimize the lost. On
the other hand, the solids product from the fermentation process was separated by
a centrifuge, followed by drying process in rotary dryer. Then, the solids products
are recovered in the evaporation process as clean condensate and concentrated syrup
(15–20% of total solids weight).
9 Conclusion
Microalgae biomass is the third generation feedstock for biofuel production. Besides
the accumulation of lipid within the microalgae cells for biodiesel production, the
stored carbohydrate also can be further utilized for bioethanol production. It is foreseen that bioethanol derived from microalgae biomass could pave a sustainable route
to substitute the gasoline in the global market. However, more researches are still
required to justify the commercial feasibility of microalgae bioethanol production,
especially the life cycle impact assessment and techno-economic analysis.
Acknowledgements We gratefully acknowledge RUSA—Phase 2.0 grant sanctioned vide Letter
No.F.24-51/2014-U, Policy (TN Multi-Gen), Dept. of Edn. Govt. of India, Dated 09.10.2018 and
financial assistance rendered to Ms. N. Rashiya in the form of a UGC – RGNF by University Grants
Commission, New Delhi [No. F1 – 17.1/2014-15/RGNF-2014-15-SC-TAM-75166].