TITLE:
A Review on 1st and 2nd Generation Bioethanol Production-Recent Progress
AUTHORS:
Radhakumari Muktham, Suresh K. Bhargava, Satyavathi Bankupalli, Andrew S. Ball
KEYWORDS:
Bioethanol, Biomass, Cellulose, Fermentation, Hydrolysis, Pretreatment
JOURNAL NAME:
Journal of Sustainable Bioenergy Systems,
Vol.6 No.3,
September
8,
2016
ABSTRACT: Today’s society is based on the use of fossil resources for transportation fuels. The result of unlimited
consumption of fossil fuels is a severe depletion of the natural reserves and damage to the
environment. Depleting fossil reserves and increasing demand for energy together with environmental
concerns have motivated researchers towards the development of alternative fuels which
are eco-friendly, renewable and economical. Bioethanol is one such dominant global renewable
transport biofuel which can readily substitute fossil fuels. Conventionally, bioethanol has been
produced from sucrose and starch rich feedstocks (edible agricultural crops and products) known
as 1st generation bioethanol; however this substrate conflicts with food and feed production. As an
alternative to 1st generation bioethanol, currently there is much focus on advancing a cellulosic
bioethanol concept that utilizes lignocellulosic residues from agricultural crops and residues
(such as bagasse, straw, stover, stems, leaves and deoiled seed residues). Efficient conversion of
lignocellulosic biomass into bioethanol remains an area of active research in terms of pretreatment
of the biomass to fractionate its constituents (cellulose, hemicellulose and lignin), breakdown
of cellulose and hemicellulose into hexose and pentose sugars and co-fermentation of the
sugars to ethanol. The present review discusses research progress in bioethanol production from
sucrose, starch and cellulosic feedstocks. Development of efficient technology to convert lignocellulosic
biomass into fermentable sugars and optimization of enzymatic hydrolysis using on-site/
in-house enzyme preparation are the key areas of development in lignocellulosic bioethanol production.
Moreover, finding efficient fermenting microorganisms which can utilize pentose and
hexose sugars in their metabolism to produce ethanol together with minimum foam and glycerol
formation is also an important parameter in fermentation. Research has been focusing on the application
of genetically modified strains, thermoanaerobes and mixed cultures of different strains
in bioethanol production from sucrose, starch and lignocellulosic feedstocks.