Conclusion
The growing need to cater the energy demand coupled with the urge to mitigate GHG footprint
in the energy sector has
necessitated inventorying of renewable and sustainable energy alternatives. Green seaweeds
have the potential to
serve as a renewable and sustainable feedstock for bioethanol production. Dilute acid,
H2SO4
is an appropriate pretreatment method for extraction of sugars from algal biomass. Algal
biomass pretreated using
dilute acid yields higher sugar during enzyme hydrolysis by exposing cellulose fibres for
enzyme degradation.
Neutralization using Na2CO3 exhibited lower sugar removal for U.lactuca (39.8%)
and
E.intestinalis (14.7%). Green seaweeds U.lactuca and
E.intestinalis are viable feedstock
for bioethanol production due to higher carbohydrate content of 62.15% and 40.1%
respectively. Saccharification and
Fermentation (SSF) process yielded higher conversion efficiency compared to SHF (Separate
hydrolysis and
fermentation) process and SSF achieved higher efficiency for U.lactuca indicating
fermentation of more than
one sugar present in the medium. Toddy yeast strain exhibited higher efficacy in
fermentation of
E.intestinalis hydrolysate in both SHF and SSF process achieving 25.8% and 77.4%
efficiency respectively.
Macroalgal biomass has potential to produce various value added products of commercial
significance in addition to
the production of biofuels. The study highlights the scope for bioethanol from macroalgae
and also the availability
of potential sites for cultivation. The comprehensive knowledge of macro algal resources
distribution, seasonality
and biochemical composition through field survey and choice of appropriate enzyme and yeast
would aid in realizing
the path of the sustainable, economical and commercially viable biofuel.
Data and accessibility
Data used in the analyses are compiled from the field. Data is anlysed
and organized in the form of table, which are presented in the manuscript. Also, synthesized
data are archived at http://wgbis.ces.iisc.ernet.
in/energy/water/paper/researchpaper2.html#ce, http://wgbis.ces.iisc.
ernet.in/biodiversity/
Competing interests
We have no competing interests either financial or non-financial.
Authors contribution
Ramachandra T V: data analysis and interpretation of data; revising
the article critically for important intellectual content; final editing
Deepthi H: Isolation and characterisation, Design of the fermentation
experiment, Carrying out experiments, analysis and interpretation of
data; and Paper writing.
Funding
This research was supported with the grant (i) ISRO-IISc Space
Technology Cell [ISTC/BES/TVR/389] (ii) Gajanana and Madhavi
Hegde [CES/TVR/GJH001] endowment for biofuel research; (iii) Indian
Institute of Science.
Research ethics
The publication is based on the original research and has not been
submitted elsewhere for publication or web hosting.
Animal ethics
The research does not involve either humans, animals or tissues.
Permission to carry out fieldwork
Our research is commissioned by the Ministry of Science and Technology (NRDMS Division),
Government of India and hence no further
permission is required as the field work was carried out in the non-restricted areas/protected
areas.
Acknowledgement
The authors are grateful to (i) ISRO-IISc Space Technology Cell [ISTC/BES/TVR/389] (ii)
Gajanana and Madhavi Hegde
[CES/TVR/GJH001] endowment for biofuel research for the financial support and (iii) the
NRDMS Division, Ministry of
Science and Technology, Government of India [CES/TVR/DST1045]; (iv) Indian Institute of
Science [R1011] for the
infrastructure support and colleagues at EWRG, IISc field station, Kumta for assistance
during the field
sampling.
We thank Sreekanth Naik and Gayatri Naik for the assistance during
the field data collection. We thank all the stakeholders of Aghanashini
estuary for actively taking part in the scientific discussions and cooperation during field
data compilation. We are grateful to the official
languages section at IISc for the assistance in language editing.