Assessment of the Potential of Some Selected Herbaceous Weeds in Bioethanol Production Using Saccharomyces cerevisiae

Abstract

This study focuses on the assessment of the potential of some selected herbaceous weeds in Bayero University Kano, Nigeria, on bioethanol production using Saccharomyces cerevisiae. The study involved the collection, pretreatment, and biological conversion of these biomass samples. The substrates were treated by washing, air-drying, and grinding. S. cerevisiae was subcultured from baker's yeast. The substrates underwent thermal, ultrasonication, and enzymatic hydrolysis to convert lignocellulosic material into fermentable sugars, with the reducing sugar content measured using UV-spectrophotometry. Optimization of fermentation conditions including pH, temperature and time were carried out to determine the optimum yield. The reducing sugar yields after pretreatment were found to be 21.17mg/g, 19.2mg/g, 23.4mg/g and 20.1mg/g for Cynodon dactylon, Panicum virgatum, Cenchrus ciliaris, and Hyperrhenia hirta, respectively, with C. ciliaris having the highest yield. C. dactylon achieved the highest ethanol yield of 6.62% at pH 4.0 and 30°C after 9 days of fermentation, indicating its potential as a primary feedstock. P. virgatum also performed well, yielding 4.07% under the same conditions, suggesting its viability as a complementary resource. In contrast, both C. ciliaris and H. hirta produced lower yields of 3.51% and 3.20%, respectively, but required only 3 days of fermentation. Statistically, there is significant difference (P<0.05) in bioethanol produced between the four substrates. It is concluded that temperature and pH played crucial roles in ethanol yield. At pH 4.0 and 30°C, C. dactylon produced the highest ethanol concentration and fermentation efficiency.  In contrast, higher temperatures and variations in pH levels generally resulted in decreased ethanol production, suggesting that optimal conditions are critical for maximizing yield.