The objective of the study was to produce bioethanol from papaw fruit peel wastes and to determine its quality to use as a cost effective natural hand sanitizer. When the blended papaw (Carica papaya) fruit peel (100g/L) was inoculated with the Saccharomyces cerevisiae (baker’s yeast- 2g/L) in the fermentation media composed of 10 g/L yeast extract, 10 g/L KH₂PO₄, 2 g/L (NH₄)₂SO₄ and 0.5 g/L MgSO₄·7H₂O and allowed for fermentation for 12-96 hours at room temperature, the bioethanol yield obtained after 24 hours, was 0.6% (V/V). The fermentation conditions were optimized by changing one factor at a time while keeping the other variables constant. When fermentation period (12 hours), ratio between air space and fermentation solution (5:1), amount of yeast inoculum (5g/L) quantity of the papaw fruit peel (15g in 100 mL) were optimized, bio ethanol yield was increased by 2.5 times (1.5% (V/V)). When different nitrogen sources (2.0g/100mL) such as peptone, soy beans, corn flour and green gram were used in the fermentation media, significantly higher ethanol yield (2.67 times) was obtained in the medium where soy bean was added. When the amount of the nitrogen source was optimized as 1g/100ml, ethanol yield was significantly increased (3.83 times, 2.3% (V/V)). When different quantities of diluted sulphuric acid was used for acidic hydrolysis as pretreatment, significantly higher ethanol yield was obtained (4.2 times) with 60ml of diluted sulphuric acid. When the pH of the medium was optimized as 5.0, significantly higher ethanol yield (6.17 times, 3.7% V/V) was obtained. When the agar well diffusion assay was performed against diverse pathogenic bacterial strains such as Escherichia coli, Staphylococcus aureus, Bacillus spp. and Pseudomonas spp. in order to determine the antimicrobial quality of bioethanol, all the bacterial strains showed the inhibition zone thus, they were sensitive for the bioethanol extract. Fungal and viral responses of the bioethanol extract need to be studied in order to determine whether this bioethanol extract could be used as a potential sanitizer.

Key words: Baker’s yeast, Bioethanol, Fermentation, Optimization, Papaw fruit wastes, Soybean