Integrated storage and pretreatment of wheat straw for biofuel production

Abstract: The study aims for the development of a Pretreatment method for wheat straw, when it is stored at low temperature. The hypothesis is that an initial disruption of the crystalline nature of lignocellulose can improve the efficiency of current pretreatment method during low temperature storage. A silo model storage of wheat straw, with high moisture, involving 3 different fungal species (Holtermanniella takashimae, Pichia anomala and Anthracophyllum discolor) andtheir combination at two different temperatures (4°C and 15°C) was tested. The microbiology of samples was studied for analyzing the effectiveness of conservation. Dilute acid treatment was done prior to the saccharification with Accellerase™ 1000 enzyme. The soluble fraction of hydrolysate was fermented in 15 ml serum flask with Saccharomyces cerevisiae.The biomass stored with combination of Holtermanniella takashimae and Pichia anomala at 4°C showed significant improvement in initial ethanol yield (2.8% increase in ethanol at P‐value<0.05) compared to the non inoculated wet control sample. A detailed study of the simple sugars released, showed that the total sugar yield for P. anomala inoculated sample was double as that of control sample (29.283g/L Vs 17.43g/L). The ethanol yield for A. discolor inoculated samples (59%) was higher than the theoretical maximum (<50%), which suggests that the saccharification may not have completed at the time of fermentation.The samples stored with P. anomala showed significant inhibition of mold and other contaminants. But the results were compared with wet non inoculated samples which were non sterile and had high microbial load (106 CFU/g of fungus, 108 CFU/g aerobic bacteria, 107 CFU/g of enterobacteria) during incubation. So it is suggested to carry out a future study with simultaneous saccharification and fermentation (SSF) to completely utilize the free sugars and with a dry stored material as control, to avoid the effect of natural microflora.