**7. Conclusion**

**Algae Classification Pre-treatment Fermenting organism, process type and process time**

*Chlorococum sp*. Microalgae Supercritical CO2 lipid extraction *Saccharomyces bayanus,* SHF, 60 h 38.30 [28]

Microalgae 0.75% (w/v) NaOH pre-treatment in120°C for 30 min *Saccharomyces cerevisiae,* SHF, 72 h 26.00 [89]

*Chlamydomonas reinhardtii* UTEX 90 Microalgae 3% H2SO4 pre-treatment in 110°C for 30 min *Saccharomyces cerevisiae* S288C, SHF, 24 h 29.10 [90]

Microalgae a-amylase (90 °C, 30 min) and glucoamylase (55 °C, 30 min) enzymatic hydrolysis *Saccharomyces cerevisiae S288C*, SSF, 40 h 23.50 [91]

Microalgae 3% H2SO4 pre-treatment in 110 °C, for 105 min *Escherichia coli* SJL2526, SHF, 24 h 40.00 [92]

Microalgae Hydrothermal degradation and a-enzymatic hydrolysis *Escherichia coli KO11*, SSF, 72 h 5.51 [93]

48 [94]

44 [95]

Microalgae H2SO4 pre-treatment *Saccharomyces cerevisiae,* SHF, 50 h

*alvarezii* Macroalgae 0.9 N H2SO4 pre-treatment in 120 °C, for 60 min *Saccharomyces cerevisiae NCIM 455*,SHF, 96 h 15.4 [96]

Macroalgae 0.2% H2SO4 pre-treatment in 130 °C, for 15 min *Saccharomyces cerevisiae* SHF, 4h 1.31 [97]

Macroalgae 2% H2SO4 pre-treatment in 120 °C for 30 min and enzymatic hydrolysis with cellulose in 40 °C *Escherichia coli KO11*, SHF, 48 h 7.90 [98]

Macroalgae Meicelase pre-treatment in 50 °C for 120 h *Saccharomyces cerevisiae IAM 4178*, SHF, 48 h 36.7 [99]

Macroalgae Thermal liquefaction in 15 MPa 200 °C for 15 min *Pichia stipitis CBS 7126*, SHF, 48 h 10.0 [100]

Macroalgae 0.1 N HCl acid pre-treatment in 121 °C for 15 min and enzymatic hydrolysis with Celluclast 1.5 L, Viscozyme L *Escherichia coli KO11*, SSF, 72 h 16.1 [101]

Macroalgae Disruption and washing in water in pH 2 65 °C *Pichia angophorae*, SHF, 48 h 0.86 [102]

Macroalgae Shredding and saccharification pre-treatment *Saccharomyces cerevisiae Ethanol Red*, SSF, 48 h 0.47 [103]

Macroalgae Shredding and saccharification pre-treatment *Pichia angophorae*, SSF, 96 h 13.2 [104]

Macroalgae 0.1 M H2SO4 acid pre-treatment in 121 °C for 1 h and enzymatic hydrolysis with cellulose and cellobiase *Saccharomyces cerevisiae*, SHF, 36 h 11.3 [105]

Macroalgae Milling and otoclave in 120 °C for 15 min *Pichia stipitis* KCTC7228 2.9 [106]

43 [107]

5.8 [108]

65 [109]

24.48 [38]

Macroalgae Enzymatic hydrolysis with cellulose and β–glucosidase *Saccharomyces cerevisiae,* SHF, 48 h

Macroalgae 0.5–1% acid pre-treatment in 121°C for 30 and 60 min *Saccharomyces cerevisiae,* SHF, 96 h

Macroalgae 3.4-4.6% H2SO4 acid pre-treatment and enzymatic hydrolysis *Saccharomyces cerevisiae,* SHF, 48 h

*Ulva lactuca* Macroalgae 2 N acid pre-treatment *Saccharomyces cerevisiae,* SSF, 48 h

*Chlamydomonas reinhardtii cw15* Microalgae 12 N H2SO4 pre-treatment *Saccharomyces cerevisiae,* SHF, 48 h

*Chlorococcum*

*infusionum*

**Table 4.** Studies of ethanol production from micro and macroalgae

*Chlamydomonas*

*reinhardtii UTEX 90*

*Chlorella vulgaris* *Schizochytrium sp* *Chlorococcum humicola*

*Kappaphycus*

*Kappaphycus*

*alvarezii* *Gracilaria salicornia*

*Gelidium elegans* *Sargassum sagamianum*

*Laminaria japonica* *Laminaria hyperborea* *Saccharina latissima*

*Laminaria digitata* *Laminaria japonica* *Laminaria japonica* *Gracilaria verrucosa*

*Gelidium corneum*

*Sargassum spp.*

**Yield (%) Ref.** 

152 Biofuels - Status and Perspective

Today, demand for fossil fuels cannot be met with current reserves and increasing oil prices with economical and political crisis and effects of global warming are led countries to use renewable energy sources. Algae as third generation feedstock have a great potential because of their characteristics. Different valuable products can be obtained from algae such as biodiesel, bioethanol, biogas, pharmaceuticals and nutraceuticals. Nowadays algae are mostly utilized for biodiesel production due to their high lipid content. However algae have also high carbohydrate content that cannot be ignored. Thus they can be utilized for bioethanol pro‐ duction directly or with the remains which are obtained after oil extraction. In this study, potential of algae as a bioethanol feedstock, important steps of bioethanol production espe‐ cially pre-treatment techniques have been mentioned. In production sections, pre-treatment techniques and fermentation processes are explained in details. Recently, bioethanol produc‐ tion from algae is very new technology and open to development. Innovative and efficient fermentation processes and pre-treatment techniques are needed to make ethanol production preferable. In conclusion, algae will with their huge potential will outclass the first and second generation feedstocks and lots of improvements for usage of it will carried out in the future.
