A novel crude glycerol assisted surfactant pretreatment strategy of chili post-harvest residue for bioethanol production

Abstract

A novel crude glycerol assisted surfactant pretreatment was evaluated for bioethanol production from chili post-harvest residue. Among the various surfactants screened crude glycerol assisted polyethylene glycol (PEG) pretreatment was found to be more effective. Various process parameters affecting pretreatment were optimized. The optimum conditions of pretreatment were crude glycerol concentration of 0.55% w/w, PEG concentration of 4.5% w/w, biomass loading of 25% w/w and incubation time of 60 min. Under optimized conditions 0.459 g of reducing sugar per g of dry biomass (g/g) was observed. The hydrolyzate is devoid of major fermentation inhibitors like furfurals, 5-hydroxymethylfurfural and organic acids like citric acid, succinic acid and propionic acid. Fermentation of the non-detoxified hydrolyzate yielded 8.60 g of bioethanol per 100 g of dry biomass with a fermentation efficiency of 36.68%.

Keywords:

• pretreatment
• biomass
• bioethanol
• saccharification
• fermentation

Acknowledgements

The authors are grateful to the Ministry of New and Renewable Energy, Government of India, New Delhi; Department of Science and Technology, Government of India, New Delhi; and Technology Information, Forecasting and Assessment Council, New Delhi, for the financial support provided to the Centre for Biofuels R&D, CSIR-NIIST, Trivandrum. Raveendran Sindhu acknowledges the Department of Biotechnology for financial support under DBT Bio-CARe scheme. Raveendran Sindhu and Parameswaran Binod acknowledge Ecole Polytechnique Federale de Lausanne for financial support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Executive summary

Composition

• Crude glycerol assisted surfactant pretreatment was found to be effective in lignin and hemicelluloses removal.

• The cellulose content in the pretreated sample is higher when compared to native sample.

Effect of different process parameters on crude glycerol assisted surfactant pretreatment of chili post-harvest residue

• The optimum conditions of pretreatment were crude glycerol concentration of 0.55% w/w, PEG concentration of 4.5% w/w, incubation time of 60 min and biomass loading of 25% w/w.

Inhibitors

• Major fermentation inhibitors like furfural, hydroxymethylfurfural and organic acids were absent.

Fermentation

• Fermentation yielded 8.90 g of ethanol with a fermentation efficiency of 36.68%.

Conclusion

• First report on crude glycerol assisted surfactant pretreatment of CPHR.

• Steps like washing, neutralization and detoxification is eliminated making the process economically viable.