**Conflict of interest**

*pombe* R3DOM and *Saccharomyces cerevisiae* R3DIM4 fermentation of sulfuric acid pretreated *Parthenium hysterophorus*. The efficiency of bioethanol production by the three microbial strains was reported as 78.84, 87.82, and 87.17%, respectively. Chandel [37] used *Pichia stipitis* NCIM3498 to ferment hydrolyzate obtained from aqueous ammonia, sulfuric acid and sodium hydroxide pretreated *Saccharum spontaneum*. The results show maximum bioethanol production from hydrolyzate for all the pretreated biomass. Gusain and Suthar [13] converted alkaline pretreated aquatic weeds into bioethanol using *Saccharomyces cerevisiae*. Bioethanol yields of between 0.189 and 0.218 g/g biomass were reported for the four different species of aquatic weeds. Prasertwasu [42] fermented hydrolyzate from sodium hydroxide pretreated *Pennisetum polystachion* with *Saccharomyces cerevisiae* (TISTR 5596) and reported high bioethanol yield after 24 hours. Ratsamee [10] also reported maximum bioethanol yield after fermenting hydrolyzate from calcium hydroxide pretreated *Panicum maximum* cv. TD 53 with

Weed biomass is a promising feedstock for economic bioethanol production. The abundance of weed biomass worldwide is an assurance of its sustainability as a feedstock. Current research on the conversion of weed biomass to bioethanol is focused on pretreatment techniques. Different pretreatment techniques have been explored to convert weed biomass into bioethanol. Maximum bioethanol yields have been reported after fermentation of hydrolyzates from pretreated weed biomass. However, current technologies are still inadequate for bioethanol production from weed biomass to compete with starch and sugar based bioethanol in terms of production yield and cost. Production of cellulosic bioethanol from weedy plants is only at the laboratory scale. Further research to establish cost effective and efficient conversion processes including pretreatment technique(s) for a wide range of weed biomass is needed. Predictive models will also aid in the selection, design, optimization, and process control pretreatment technologies that match biomass feedstock with appropriate method and process configuration. On the other hand, active research is going on to ensure commercial production of bioethanol from weed biomass. This includes improvements in pretreatment technologies, specific activities of enzymes as well as isolation of new fermentation microorganism from natural environment. With strong support from various governments, bioethanol production

from weed biomass will play a major role in meeting energy demand globally.

The author would like to devote this chapter to Emeritus Prof. Dr. Norio Takamura, Emeritus Prof. Dr. Kazuhiko Sameshima and Prof. Dr. Yoshito Ohtani, all of Kochi University, Nankoku, Japan, Emeritus Prof. Dr. Kazuhiko Ogino (Former Dean of United Graduate School Ehime, 1991–1993), Emeritus Prof. Dr. Sanro Tachibana, Ehime University, Matsuyama, Japan, and Emeritus Prof. Dr. Ryuichiro Kondo, Kyushu University, Fukuoka, Japan for their immense

*Saccharomyces cerevisiae* TISTR 5596 for 48 hours.

94 Fuel Ethanol Production from Sugarcane

**4. Conclusion and future perspectives**

**Acknowledgements**

The author has no conflict of interest to declare.
