Due to the existing energy crisis and scarcity of conventional supplies of fossil fuels, there is a strong desire for the production of bioethanol from sustainable biodegradable waste as an alternative energy source . The aim of this study was to produce bioethanol from grain waste flour (GWF), Tella spent (TS), pineapple (PAP) and papaya peels (PYP) using native yeasts isolated from Ethiopian traditional alcoholic beverages . Diluted H 2 SO 4 was used to hydrolyze polysaccharides in the waste materials. Starch content from GWF and reducing sugar concentration from each hydrolysate were determined by the standard protocol. Seventy-five native yeasts were isolated from local beverages for ethanol production . The 2% H 2 SO 4 pretreatment produced the highest reducing sugar of GWF (30.1%); PYP (28.6%); PAP (16.4%); and TS (10.4%). In addition to this, GWF had 60.6% starch content. Of 75 isolates, 12 were able to tolerate ≥8% ethanol concentration, and 2 isolates, Y10 and Y55 showed strong ethanol production capacity (glucose to ethanol conversion efficiency) with 8.2% (79.8%) and 9.6% (94.3%) from synthetic medium, respectively. The highest ethanol yields of 16.1%, 9.8%, 8.0% and 6.1% were produced from GWF, PAP, PYP and TS, respectively using isolate, Y55 (identified as S. cerevisiae ) within 168 h for GWF, 120 h for PAP and 72 h for PYP and TS. This study revealed that native yeast isolates could be used for industrial production of bioethanol via cheap biodegradable wastes.
A method was proposed to enhance the growth of Saccharomyces cerevisiae cells and increase the alcohol yield. This strategy utilized nanozymes, specifically FeCo-Prussian blue analogue nanoparticles (FeCo-PBA NPs), FeCo-N-C, CoSO porous nanocubes (CoSO PNCs), and FeN3P-single-atom nanozymes (FeN3P-SAzyme), to mimic the antioxidant enzymes. When subjected to H2O2 stress, the nanozymes significantly stimulated cell growth and effectively reduced the levels of reactive oxygen species (ROS), as evidenced by the decrease in the malondialdehyde (MDA) content. Additionally, the decline in lactate dehydrogenase (LDH) activity within the fermentation environment suggested that nanozymes provided protection against cell membrane damage caused by H2O2. This protective effect can be attributed to their inhibitory impact on ROS production. Further results demonstrated that 50 μg mL–1 of nanozymes led to an increase in the ethanol yield and total alcohol yield in S. cerevisiae. This approach held great potential for enhancing alcohol production efficiency in the S. cerevisiae industrial fermentation process.
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