An innovative recyclable deep eutectic solvent-ultrasound pretreatment of pineapple leaf waste biomass for enhanced bioethanol production

The non-conventional fossil fuels despite serving as significant contributors to modern energy needs have raised concerns due to their adverse environmental effects and rapid depletion, prompting both the scientific community and governments to seek renewable energy sources, such as biofuels. Pineapple leaf (PL) waste biomass represents an appropriate feedstock for biofuel production owing to its abundance, energy efficiency, and sustainability. The current study investigated the use of an ultrasound-assisted deep eutectic solvent (DES) pretreatment, choline chloride (ChCl):ethylene glycol (EG) (1:5), to improve sugar yield from pineapple leaf biomass for bioethanol production. The ultrasound-assisted ChCl-EG pretreatment improved the enzymatic hydrolysis efficiency, achieving a higher glucose yield of 448 mg/g biomass and 466.17 mg/g PL biomass total reducing sugar with 5% (w/v) substrate loading. Using the recycling process, the pretreatment efficiencies of the recycled DES (ChCl-EG) were maintained with a marginal cellulose decrease of 15.44% after five DES recycles. The dual yeast culture demonstrated superior fermentation efficiency (60.06%), with an ethanol yield of 229.43 mg/g biomass. The mass balance analysis further provided valuable insights into using an integrated ultrasound-DES pretreatment, highlighting its potential for sustainable biofuel production from pineapple leaf waste. The novelty of ultrasound-assisted DES pretreatment for PL biomass lies in its enhanced lignocellulosic breakdown, offering a greener alternative by improving DES penetration and lignin removal, increasing cellulose accessibility, and boosting bioethanol production efficiency.