Integrated storage and pretreatment of wheat straw with different fungi : impact on ethanol production and storage microflora

Sammanfattning: Production of ethanol using cellulosic material as feedstock is crucial for sustainable fuel ethanol production.However a production process based on cellulosic biomass involves several energy and cost intensive steps like storage of biomass, pretreatment, hydrolysis and fermentation, where pretreatment is the energy intensive and troublesome step. This project aimed for an integration of storage and pretreatment step, to get more energy efficiency and more ethanol yield. In the present investigation wheat strawwas used as a model and wasstored in moist conditions with different fungal species (Pichia anomala, Pichia stipitis, and Anthracophyllum discolor) inoculated separately in mini-silos for 1 month at 15°C and 4°C. Simultaneous saccharification and fermentation was carried out afterthe storage period andethanol yields were compared with dry wheat straw as a control.A7.52 % higher ethanol yield (compared to the dry wheat straw) was obtained from wheat straw incubated by P. anomala at 15°C, and 6.87 % higher ethanol yield from P.stipitis inoculated wheat straw incubated at 4°C showed ISP can result in increasing the ethanol yield. Also it was obvious from the study that, the release of sugar from integrated storage and pretreatment (ISP) sample was fasterthan from the traditional sample. The higher concentration of non-fermentable sugars (eg: xylose, arabinose, mannose etc.) left during fermentation of ISP samples indicate that the ISP process causes more structural damage to the cellulosic substances and produces more sugar release than the control. Moreover P. anomala and P.stipitis showed a biocontrol activity during moist storageby preventing growth of other fungi and enterobacteria in the wheatstraw during the one month incubation. In conclusion, ISP acted as an efficient method of storage and resulted in higher ethanol yield.