Utilization of waste product from water chestnut stems to produce bioethanol
Nguyen Phuoc Minh
Bioethanol is one of the most promising replacements for fossil fuel since it is renewable and emits 85% less green-house gases compared to gasoline. Water chestnut (Trapa natans L., sensu lato) is an annual, ﬂoating-leaved aquatic plant of temperate and tropical freshwater wetlands, rivers, lakes, ponds, and estuaries. Water chestnut corm is used for human consumption. The remaining part is waste product being discarded and abundant in environment. Purpose of our research is to utilize this waste to product bioethanol. The dried water chestnut stem has moisture 10%; including cellulose 24.07%, hemicellulose 37.19%, lignin 7.82% and 30.92% others. The primary treatment of water chestnut stem powder is hydrolized by H2SO4 0.5% at 121oC in 1 hour with ratio material: acid 1:10 (w/v) to get high reduced sugar 4g/l. Actinobacteria ACT 06 is used for hydrolysis and yeast SA.03 is used for fermentation. Actinobacteria ACT 06 is well performed at 35- 50 0C in neutral pH. At 3% supplementation, they can decompose CMC cirlce at diameter 40 mm after 3 cultivation days, cell density 8.53x108 CFU/ml and sugar concentration 5.10 g/l. Reduced sugar transformation efficiency 70-75% is noticed when fermenting at reduced sugar 3.0-5.0 g/l. Bioethanol is formed at 1.9-4.2% so we can consider water chestnut stems as potential material for bioethanol production.