The single-batch bioconversion of wheat straw to ethanol employing the fungusTrichoderma viride and the yeastPachysolen tannophylus

We have developed and optimized a single-batch process for the production of ethanol from wheat straw employing the fungusTrichoderma viride and the yeastPachysolen tannophylus. T. viride andAspergillus niger were examined for their ability to produce fermentable sugars from cellulosic waste materials, e.g. different kinds of straw and wood waste.T. viride most efficiently saccharified delignified wheat straw within 3 days at 25–30°C with a yield of reducing sugars of 27 g from 50 g delignified wheat straw. The resulting wheat straw hydrolysates contained xylose and glucose in a 1:1.6 molar ratio. After heat inactivation of fungal activities the sugars were converted to ethanol by the oxygen-tolerant yeastP. tannophylus in the same batch. Under the optimized conditions developed (all weights are per liter) 70 g natural untreated wheat straw (100%) yielded 50 g delignified straw (71.4%), which was saccharified to 27 g reducing sugars (38.6%). Fermentation of the sugars yielded 11.8 g ethanol (16.9%) and followed the molar equation: 1 xylose + 1.6 glucose 5.3 ethanol + 5.6 CO₂.