Bioethanol production from non-edible de-oiled Pongamia pinnata seed residue-optimization of acid hydrolysis followed by fermentation

Published Date
Industrial Crops and Products
30 December 2016, Vol.94:490–497, doi:10.1016/j.indcrop.2016.09.019

• Author 

• Radhakumari Muktham ^a,b
• Andrew S Ball ^a
• Suresh K Bhargava ^a
• Satyavathi Bankupalli ^b,,,

• aSchool of Science, RMIT University Bundoora 3083, Australia
• bChemical Engineering Division, CSIR-Indian Institute of Chemical Technology Hyderabad 500 007, India

Received 10 May 2016. Revised 29 August 2016. Accepted 8 September 2016. Available online 16 September 2016. 

Highlights

• •
  Pongamia pinnata seed residue represents a promising source for ethanol production.
• •
  Effect of H₂SO₄, HCl and H₃PO₄ on P. pinnata seed residue hydrolysis was studied.
• •
  Acid treatment for 60 min was used for hydrolysis of P. pinnata seed residue.
• •
  41% of theoretical maximum ethanol was formed from the seed residue conversion.

Abstract

De-oiled Pongamia pinnata seed cake has been gaining attention as a promising feed stock for ethanol production owing to the large amounts of carbohydrates (42% w/w) present in the seed biomass. This, coupled with the potential of seed productivity (>200,000 t annum⁻¹) makes it suitable for the sustainable production of ethanol. The present research explores the application of glucose obtained from acid hydrolysis of the seed cake for ethanol production in a three step process: acid treatment, neutralization and fermentation. The Taguchi robust design of experiments was employed to study the effects of the parameters including acid type (H₂SO₄, HCl, H₃PO₄), acid concentration (2–6% w/w), and temperature (80–100 °C) on the formation of glucose. Among the reaction variables considered, acid concentration and temperature showed a positive effect on glucose release from the biomass with HCl the best catalyst compared to H₂SO₄ and H₃PO₄ showing highest glucose formation (173.4 g kg⁻¹ seed residue) at 100 °C with 6% w/w HCl concentration. The energy required for this pretreatment was estimated to get an insight into the process energy demand (1080–1110 KJ kg⁻¹ of seed cake). Downstream processing before fermentation included neutralization. Fermentation of hydrolysis product obtained from 2%, 4% and 6% HCl treatments (carried out using Saccharomyces cerevisiae) gave 67.52, 74.98 and 88.62 g ethanol kg⁻¹ dry seed residue, respectively, corresponding to ∼31.45%, 34.92% and 41.28% of theoretical ethanol (214 g kg⁻¹) formation, calculated based on ethanol produced per gram of carbohydrate in the seed residue.

Keywords

Acid hydrolysis

Bioethanol

Fermentation

Glucose

Lignocellulosic biomass

Taguchi method

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• ⁎ 
  Corresponding author.

© 2016 Elsevier B.V. All rights reserved.

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