Bioethanol production from acid pretreated microalgal hydrolysate using microwave-assisted heating wet torrefaction

Kai Ling Yu, Wei Hsin Chen, Herng Kuang Sheen, Jo Shu Chang, Chih Sheng Lin, Hwai Chyuan Ong, Pau Loke Show, Tau Chuan Ling

Research output: Contribution to journalArticlepeer-review

58 Scopus citations


This study focused on the bioethanol production from the co-production of solid biochar and liquid hydrolysate under microwave-assisted heating wet torrefaction towards a sustainable green technology. The two indigenous microalgal biomass undergone dilute acid pretreatment using wet torrefaction to produce microalgal hydrolysates and biochar at operating conditions of 160–170 °C with holding times of 5–10 min. The hydrolysates were utilized for fermentation with the yeast Saccharomyces cerevisiae at 29 °C in a dark condition at a non-agitation state for 120 h. The concentrations of total reducing sugar, reducing sugar by-product, and bioethanol in the hydrolysates were determined. The carbohydrate-rich microalga C. vulgaris ESP-31 showed a good performance in bioethanol production. Microalgal hydrolysate obtained after the pretreatment consisted of a total reducing sugar with the highest concentration of 98.11 g/L. The formation of by-product 5-hydroxymethyl-2-furaldehyde (5-HMF), which might act as the fermentation inhibitor that led to the low ethanol yield, was also analyzed. The highest ethanol yield achieved was 7.61% with a maximum experimental conversion probability of 95.22%. This study has demonstrated the feasible bioethanol production from microalgal hydrolysate through microwave-assisted heating wet torrefaction using dilute acids and the optimization of bioethanol production can be carried out for better performance in the future study.

Original languageBritish English
Article number118435
StatePublished - 1 Nov 2020


  • Acid hydrolysis
  • Alternative fuel
  • Bioethanol and biochar
  • Hydrolysate
  • Microalgae
  • Wet torrefaction


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